The Immunogenetics of Autoimmune Diabetes and Autoimmune Thyroid Disease

and suppressor cell induction. Immunol Rev 106:93-111. Iwatani Y, Amino N, Miyai K: 1989. Peripheral self-toleranceand autoimmunity: the protective role of expression of class II histocompatibility antigens on non-lymphoid cells. Biomed Pharmacother 43:593+05. Kohn LD, Giuliani C, Montani V, et aL: 1995. Antireceptor immunity In Rayner DC, Champion BR, eds. Thyroid Autoimmunity Austin, TX, RG Landes, pp 115-170.

ResetkovaE, Nishikawa M, Mukuta T, Arreaza G, Fournasier V, Volp6 R: 1995. Hc~mingof sICR-labeledhuman peripherallymphocytes to Graves’ thyroid tissue xenografted into SCID mice. Thyroid 5:293-298. Satoh J, PrabhakarBS, Haspel m, (;insbergFellner F, Notkins AL: 1983. Human monoclinal autoantibodiesthat reactwith muftiple endocrineorgans.N Engl J Med 309:217–230. TLanJ,AtkinsonM, Clare-SafzlerM, et id.: 1995. GAD based immunotherapies for murine IDDM [abst]. Autoimmunity 21:68.

LeslieRDG, CarotenutoP,Pozzilfi P: 1993. New developments in non-specific and semi-specific immunosuppression in type I diabetes. Diabetes Metab Rev 9:257-267.

Tomer Y, Davies TF: 1993. Infection, thyroid disease and autoimmunity. Endocr Rev 14: 107-120.

Martin A, Davies TF: 1992. T cells in human autoimmune disease: emerging data shows lack of need to invoke suppressorT cell problems. Thyroid 2:247-261.

Viselli SM, Stanziale S, Shults K, Kovacs WJ , Olsen NJ: 1995. Castration alters peripheral immune function in normal male mice. Immunology 84:337–342.

McGregor AM: 1992. Autoimmunity in the thyroid:can the molecufarrevolutioncontribute to our understanding?Q J Med 82:1–13.

Volp6 R: 1990. Autoimmune diseases of the endocrine system. Boca Raton, FL, CR.CPress, pp 1-364.

MukutaT,YoshikawaN, ArreazaG, et al.: 1995. Activation of T cell subsets by syntheticTSH receptor peptides and recombinant glutamate decarboxylase in autoimmune thyroid disease and insulin dependent diabetes mellitus. J Clin Endocnnol Metab 80:1264-1272. Murakami M, MiyashitaK, Monden T,Yamada M, Iriuchijima T, Mori M: 1993. Evidence that a soluble form of the TSH receptor is present in the peripheral blood of patients with Graves’ disease. In Nagataki S, Mori T, Tonzuka K, eds. EightyYearsof Hashimoto’s Disease. Amsterdam, Elsevie~pp 19-25. Nepom GT: 1990. A unified hypothesis for the complex genetics of HLA associations with IDDM. Diabetes 39:1153–1157. Nepom GT, Erlich H: 1990. MHC class II molecules and autoimmunity. Annu Rev Immunol 90:493–525. Olsen NJ, Watson MB, Henderson GS, Kovacs WJ: 1991.Androgen deprivationinduces phenotypic and functional changes in the thymus of adult male mice. Endocrinology 129: 2471-2476.

Volp6 R: 1992.A perspectiveon human autoimmune thyroid disease: is there an abnormality on the target cell that predisposes to the disorder? Autoimmunity 12:3-9. Volp&R: 1993. Suppressor T lymphocyte dysfunction is important in the pathogenesis of autoimmune thyroid disease.Thyroid 3:345– 350. Volp6 R: 1994a. Immunoregulation in autoimmune thyroid disease. Thyroid 4:373–377.

Volp4 R 1994b. Autoimmune endccrinopathies: aSWCtS ofpathogenesisand theroleof immune assaysin investigationand management.Clin Chem 40:2132-2145. Volp6 R: 1995. Human autoimmune thyroid disease: recent advances. In Rayner DC, Champion BR, eds. Thyroid autoimmunity Austin, TX, RG Landes, pp 199-230. Volp6R, KasugaY,Akasu~ MoritaT,Resetkova E, ArreazaG: 1993.Theuse of theSCIDmouse and the nude mouse as models for thestudyof human auto” mmmne thyroiddisease.Clin hnmunol Immunopathol 67:9>99. Wachtel SS, Koo GC, Boyce EA: 1975. Evolutionaryconservationof HY male antigen.Nature 254:270–274. WeetmanAP: 1995a.The effect of treatmenton autoimmune thyroid disease. In Rayner DC Champion BR, eds. Thyroid Autoimmunity. Austin, TX, RG Landes, pp 170-198. Weetman AP: 1995b. Review: antigen presentation in the pathogenesis of autoimmune thyroid disease. J Autoimmun 8:305–312. WeetmanM, McGuegorAM: 1994.Autoimmune thyroid disease: further developmentsin our understanding.Endocr Rev 15:788-830. YoshikawaN, Arreaza G, Morita T, et aL: 1994. Effect of removing human Graves’ thyroid xenografts after eight weeks in nude mice and rexenografting them into SCID mice. J Clin Endocnnol Metab 78:367-374. TEM

The Immunogenetics of Autoimmune Diabetes and-Autoimmune Thyroid Disease Yaron Tomer, Giuseppe 13arbesino, David Greenberg, and Terry F. Davies

PlotnikoffN, Murgo A, FaithR, Wybran J: 1991. Stress and immunity. Boca Raton, FL, CRC Press, pp 1-558.

Although medical genetics is a well-developedarea of interest, relatively little is known about the diseases caused by the combination of many genes. These multiinfluenceddiseasesinclude the autoimmune endocrine diseases. Recent advances in the techniques for whole-genome screening have shown a varietyof loci thatare linkedto the development of insulindependent diabetes mellitus,and similardata are likely to be soon generated in autoimmune thyroiddisease.Here, the authors survey the current stateofgenetic knowledgein these two areasand descn”bethe investigative and analyticaltechniques that are now available. (Trends Endocrinol Elsevier Science Inc. Metab 1997; 8:63–70). 01997,

Ramiya V MackuwnN, Muir A, WasserfallC, Shang XZ, Schatz D: 1995. Auto-antigenspecific immunothempiesin the preventionof diabetesin NOD mice [abst].Autoimmunity21: 68.

Yaron Tomer, Giuseppe Barbesino, David Greenberg, and Terry F. Davies are at the Division of Endocrinology and Metabolism, Department of Medicine, and the Department of Psychiatry, Mount Sinai School of Medicine, New York, NY 10029, USA.

PetterssonA, Wilson D, Daniels T, et al.: 1995. Thyroiditis in the BB rat is associated with lymphopenia but occurs independentlyof diabetes. J Autoimmun 8:493–505. Phillips D, McLachkin S, StephensonA, et al.: 1990.Autosomaldominanttransmissionof autoantibodiesto thymglobulinand thyroidperoxidase.J Clin Endocrinol Metab 70:742–746.

TEM vol.8, No. 2, 1997

@ 1997,ElsevierScienceInc., 1043-2760/97/$17.00 PIIS1043-276O(96)OO266-4

63

The autoimmune endocrine diseases are multifactorial diseases that may develop as a result of an interplay between a specific genetic background and an environmental insult. The genetic susceptibility may serve as a platform on which environmental agents (for example, infectious organisms) can induce the disease (Tomer and Davies 1995). Complex, or multifactorial, diseases are likely to have several ~emetic influences, including interacting genes, disease heterogeneity, and variable degrees of penetrance, making the identification of susceptibility genes for these diseases difficult. New developments in molecular biology and genetic analysis, however, have opened the way to identifying susceptibility genes of complex diseases. Indeed, the first successful utilization of new genetic approaches has led to the identification of several susceptibility markers for insulin-dependent diabetes mellitus (IDDM) (Davies et al. 1994), This review examines some of the data on the genetic susceptibility to autoimmune endocrine diseases, focusing on these recent developments and the future directions in the search for the susceptibility genes of IDDM and the autoimmune thyroid diseases (AITD).

●

Looking for Evidence of Genetic Susceptibility

Evidence for a genetic contribution to a disease may be sought in a wide variety

of ways. At the simplest level, a family history of the disease may indicate a genetic component, although an environmental agent may also be involved. If, however, the family history suggests Mendelian inheritance, as for example with thyroid autoantibodies (Phillips et al. 1991, Shields et al. 1994), then a genetic contribution can be confirmed by a genome search. Additional information can be obtained from identical (monozygous) twin studies, which may demonstrate that the disease is present in both twins more often than the expected disease prevalence. Although an environmental contribution could only be excluded in studies of separated twins who develop the disease more than expected, such data do provide a unique view of disease penetrance. Because both twins inherit the same genetic repertoire, if 50Y0 of them develop an autoimmune disease, the usual interpretation is to

64

conclude that the penetrance of those genes occurs in 50% of the individuals who inherit them, although this assumes no genetic heterogeneity. Twin studies have, therefore, contributed critical data to statistical analyses of endocrine genetics. Other simple ways of analyzing genetic contributions to disease etiology may come from the study of different ethnic populations. For example, non– insulin-dependent diabetes mellitus (NIDDM) appears to be more common in American Indians and African Americans (Bennett et al. 1976, Freedman et al. 1995). Even within ethnically homogeneous populations, geographic relationships with disease have been observed, suggesting either an environmental contribution or the development of new gene repertoires (Gamble 1980). At a more fundamental level, many investigators have studied human leukocyte antigen (HLA) haplotypes and showed clear associations wit%a tiety of autoimmune diseases, Stmlies that have been widely reviewed (Nelson and Hansen. 1990). As a development of such studies, we now have the ability to examine markers other than HLA within the genome and to assess their relevance for the disease under investigation, always remembering that statistical corrections need to be applied when many markers are being examined simuhaneously. Indeed, searching the entire human genome for such markers is now possible. The differences between association and linkage are discussed in detail later here, but both types of analyses indicate the presence of a genetic component in disease etiology

●

Linkage and Association Analyses

The two approaches used to study susceptibility genes of complex diseases are association and linkage analyses. Association studies are ideal for locating genes that increase the risk for the development of the disease but may not be necessary for the development of the disease. Association studies are performed in the simplest case by comparing the frequency of the specific phenotype of the marker studied (for example, HLA DR-3) in patients having the disease with the frequency of that marker in an ethnically similar disease-free population. Common techniques for testing for association include the haplotype rela-

tive risk and transmissiorddisequilibrium tests (Falk and Rubinstein 1987, Spielman et al. 1993). In contrast, linkage studies are powerful took in analyzing disease-related genes because they detect genes that are directly involved in the pathogenesis of the disease, that is, genes that are required (but perhaps not sufficient) for the development of the disease (Greenberg 1993). The principle of linkage analysis is based on the fact that if two genes are close enough on a chromosome, they will tend to segregate together; therefore, if a marker is close to a disease-related gene, this marker will cosegregate with the disease in families. The lod score is the measure of the likelihood of linkage between a disease and a genetic marker (Ott 1996). The great advantage of linkage analysis is that it identifies genes that are necessary for disease expression (that is, an individual must inherit these genes in order to develop the disease) (Greenberg 1993). Both association and linkage have been utilized to study the genes of IDDM and AITD.

●

Measuring Linkage

If a marker is close to a disease susceptibility gene, this marker will cosegregate with the disease within families. A lod score of >3 is considered strong evidence of linkage and a lod score of –2 is considered strong evidence against linkage between the marker and the trait or disease (Ott 1996). Two analytical approaches can be taken. These are the parametric approach (likelihood maximization or standard lod score analysis) and the nonparametric approach (affected sib pair analysis). Likelihood maximization is the more powerful approach. It has the disadvantage that a mode of inheritance must be assumed for the analysis, and therefore, assuming several different sets of genetic parameters is usually necessary. Having to test multiple genetic parameters increases the type 1 error, but recent work has shown that this increase is minimal (Knapp et al. 1994). Lod score analysis has important advantages for the study of autoimmune endocrine disease because it (a) allows a way to test for the presence of heterogeneity within the data set, (b) allows the deduction of the mode of inheritance and penetrance from the linkage data, and (c) allows the testing of whether the

@ 1997,ElsevierSiciemce he., 1043-2760/97/$17.00 PIIS1043-276O(96)OO266-4

TEM vol. 8, No. 2, 1997

presence of autoantibodies in unaffected family members is related genetically to the disease genotype. Hence, when there is expected disease heterogeneity and the opportunity to measure disease markers such as autoantibodies, then the traditional parametric analysis under differing assumptions of dominant and recessive inheritance may be the most appropriate.

●

Genotypingin the Search for SusceptibilityGenes

As a consequence of the Human Genome Program, it is now straightforward to identify genes for diseases that have a simple Mendelian genetic basis. The approach is to “type” individuals in suitable families using a “genome screen” of genetic markers (microsatellites) covering the entire genome and to observe which markers segregate with the disease. It is only recently that microsatellites were also shown to be a powerful tool for linkage analysis of more complex inherited diseases (Weber 1990). In practical terms, microsatellites are regions in the genome that are composed of repetitive sequences. The most common microsatellites are the CA-repeats (dC-dA).; however, microsatellite loci are highly polymo~hic, owing to variation in the number of repeats (usually there are 5–15 alleles per locus), and they are uniformly distributed throughout the genome at distances of less than 1 million base pairs (Weber 1990) (Figure 1A and B). Therefore, microsatellites can serve as excellent markers in linkage studies designed to search for unknown disease susceptibility genes. The SUSpected gene region can then be further narrowed with the use of denser markers and cloning techniques applied so that the gene can be identified.

●

Insulin-Dependent Diabetes Mellitus (IDDM)

IDDM results from an autoimmune destruction of the islet P cells. The autoimmune etiology of IDDM has been reviewed elsewhere (Falorni et al. 1995) and is suggested by several findings: 1. The presence of inflammatory cell infiltratesin the islets (Botazzo 1984). 2. The detection of islet cell antibodies and islet specific T cells in approxiTEM vol.8, No. 2, 1997

mately 80Vo of the patients (Cahill and McDevitt 1981). 3. The finding of autoimmune reactions to organs other than the endocrine pancreas in 1OVO–15Y0 of the patients (Torfs et al. 1986). 4. The strong association with certain HLA alleles (see later here). 5. The response to immunosuppression (for example, cyclosporin) (Bougneres et al. 1982). A large body of indirect evidence points to a genetic susceptibility for IDDM, including epidemiological studies in families, twin studies, animal studies, and association and linkage studies in families. We now have, therefore, direct evidence of a genetic predisposition for the development of autoimmune diabetes. Population and Family Studies IDDM is much more prevalent in whites than in other ethnic groups (for example, African Americans, Japanese, and Chinese) (West 1978). The prevalence of IDDM in the United Sstates is 0.26Y0 by age 20 (LaPorte et al. 1981). The Pittsburgh study demonstrated that the incidence of IDDM was 16:100,00 for white males and 10: 100,000 for nonwhite males (LaPorte et al. 1981). There is also evidence for familial clustering of IDDM, albeit not as commonly as in AITD. Approximately 4%1070 of patients with IDDM have a first-degree relative with the disease (Tattersall and Fajans 1975, Wagener et al. 1982). Interestingly, offspring of IDDM diabetic fathers are at much higher risk for autoimmune diabetes than are the offspring of IDDM mothers. This risk is not the result of a selective loss of diabetes-susceptible fetuses in the perinatal period (Warram et al. 1984).

Twin Studies Investigations of twins are the classic method of studying genetics of human diseases. The twin studies provide information concerning the inheritance of a disease and can also yield certain quantitative evaluations of the etiological significance of heredity in relation to exogenic factors. The twin method is based upon comparison of concordance (disease in both twins) of a given disease among monozygotic (MZ) twins with concordance among dizygotic (DZ) twins. If concordance is

higher in the MZ twins when compared with the DZ twins, it suggests a hereditary component. The discordance among the MZ twin pairs indicates that the gene or genes concerned show reduced penetration; that is, certain factors must occur or be present before the disease becomes manifest. The concordance rate in MZ twins can give an estimate of the penetrance of the disease and is useful for studies of multifactorial diseases such as IDDM and AITD, in which reduced penetrance must be assumed in the linkage analyses. Twin studies in diabetes have shown a concordance rate of 300/o–500/o in MZ twins and about 50/0in DZ twins (Tattersall and Pyke 1972, Barnett et al. 1981). These results indicate a genetic contribution to the pathogenesis of IDDM; however, the relatively high (more than 50%) discordance rate among MZ twins suggests that environmental factors must also play an important role in the development of the diseases (Tomer and Davies 1995). Human LeukocyteAntigen Studies in Insulin-DependentDiabetesMellitus A positive association was first detected between IDDM and HLA-B8 (Singal and Blajchman 1973). This association was later shown, by stronger associations, to be due to linkage disequilibrium between these class I alleles and class II alleles. About 950/0of Caucasian diabetics are HLA-DR3 and/or DR4, compared with 450/o–550/o of controls (Spielman et al. 1980, Nerup et al. 1987). Recent analyses have shown that the extended hapDR4-DQA1*0301-DQB1‘0302 lotypes and DR3-DQA1*0501-DQB 1*0201 are strongly associated with IDDM. On the other hand, DR15-DQA1*O1O2-DQB1* 0602 demonstrates strong negative associations with IDDM (Kockum et al. 1993). The sequencing of HLA alleles has shown that if an aspartic acid residue occupies position 57 in both alleles of that chain, autoimmune diabetes will not occur (Todd et al. 1987). Full susceptibility requires both alleles to be Asp57negative. It is hypothesized that an aspartic acid at position 57 on the P chain influences the antigen-binding properties of the HLA-DQa~ heterodimer (Brown et al. 1993). In addition to the associations between HLA and IDDM just described, several linkage studies have also been performed, confirming

01997, ElsevierScienceInc., 1043-2760/97/$17.00 PIIS1043-276O(96)OO266-4

65

primerA

A

5’

(dC-dA)n

~

3’

3’

(dG-dT)n

~

5’

primerB

LOCUS B

ac

Id cc 1’1 bc

II bc

bc

Figure 1. (A) A microsatellite is a polymorphic locus consisting of a short segment of repetitive sequences, most commonly CA-repeats (dC-dA).. Microsatellite loci polymorphisms can be analyzed by polymerase chain reaction (PCR) amplification of the locus using two primers that flank the CA-repeat segment. (B) One of the primers is labeled (by 32Por by a fluorescent dye), and the PCR products are electrophoresed on a sequencing gel and separated according to size. In the figure, the =p-labeled products are demonstrated by autoradiography. The haplotypes ‘f a multiplex family are shown.

Insulin Gene Region Polymovhisms and Susceptibility to Insulin-Dependent DiabetesMellitus The first locus outside the HLA region that was consistently found by several 66

groups to be associated with IDDM was the insulin gene region on chromosome 1lp15. Most studies reported that the insulin gene region polymorphisms conferred a risk independent of HLA genotype (Bell et al. 1984, Bain et al. 1992, Van der Auwera et al. 1993, Lucassen et al.1993, Hashimoto et al.1994). The disease-associated locus has recently been mapped to a 4. l-kb region encompassing the insulin gene (Lucassen et al. 1993) and is now designated IDDM-2 (Davies et al. 1994). This region was

bd

II cd

bc

linkage of HLA-DR to IDDM, mostly assuming a recessive mode of inheritance (Rich et al. 1987). Hence, the HLA-related gene region provides an important contribution to the genetic susceptibility of IDDM and is often referred to as diabetes susceptibility gene IDDM-1.

H

ac

found to contain 10 polymorphisms, including restriction sites and a variable number of tandem repeat (VNTR) polymorphisms (Undlien et al. 1995). In a recent study of Finnish IDDM patients, it was demonstrated that of these polymorphisms only those at –23 Hph 1, and the VNTR sites conferred significant relative risk (Undlien et al. 1995). The VNTR polymorphisms are located adjacent to defined regulatory DNA sequences, affecting insulin gene expression (Docherty 1992). Therefore, it was postulated that the biologically important polymorphisms were within the VNTRS. Indeed, it has been shown that the VNTRS can influence insulin gene expression in vitro (Kennedy et al. 1995), as well as in vivo (Bennett et al. 1995). How such an influence may affect the onset or progression of islet cell autoimmune disease is unclear at present.

@ 1997,ElsevierScienceInc., 1043-2760/97/$17.00 PIIS1043-276O(96)OO266-4

TEM vol.8, No. 2, 1997

Genome-WideSearchfor Susceptibility Genesin Insulin-Dependent Diabetes lvlellitus

roid function caused by generation of thyroid-antigen–specific T lymphocytes, production of thyroid autoantibodies, and infiltration of the thyroid gland by immune effecters cells. The AITDs are among the commonest human autoimmune disorders, affecting up to 50/oof the general population (Vanderpump et al. 1995, Hawkins et al. 1980, Tunbridge et al. 1977). The most common form of AITD is Hashimoto’s thyroiditis (Hashimoto’s disease), which manifests by hypothyroidism. Hashimoto’s disease is characterized by infiltration of the thyroid by lymphocytes, gradual destruction of the gland associated with cytotoxic T cells, and production of various secondary polyclonal thyroid autoantibodies, notably antithyroid peroxidase (TPO) and antithyroglobulin (Tg) (Levine 1983). At the other end of the spectrum is Graves’ disease, which manifests by hyperthyroidism and diffuse goiter with or without an associated orbitopathy and dermopathy (Davies 1996). Graves’ disease is caused by the production of TSH receptor autoantibodies that stimulate the TSH receptor (TSHR) to increase iodide uptake and cAMP production, inducing production and secretion of excess thyroid hormones (McDougall 1991).

The HLA and insulin region-associated genes could not completely explain the genetic susceptibilityto IDDM. Moreoveq studies in nonobese diabetic (NOD) mice suggested the existence of additional susceptibility genes (Aitman and Todd 1995, Todd et al. 1991). Therefore, severalindependent groups have utilized microsatellite polymorphic markers in order to perform a genome-wide screen for susceptibility genes for IDDM. As discussed earlier here, microsatellitesare regions in the genome that are composed of short repetitive units—from one to five base pairs. Microsatellites are abundant and uniformly distributed throughout the genome at distances of less than 1 million base pairs (Weber 1990). Therefore, microsatellitescan serve as excellent markers in linkage studies designed to search for unknown disease susceptibilitygenes. It is important to remember that complex disease genes may only increase the risk of the disease, do not cause illnessby themselves,and may be present in healthypersons. Microsatellite markers have now been used for such studies on IDDM families with affected sib pairs. Using this approach, the central role of the HLA (IDDM-1), and the insulin gene (IDDM-2), regions in genetic susceptibility to IDDM was confirmed by demonstrating linkage ● Evidence for a Genetic Susceptibilityto Autoimmune of IDDM to these loci. In addition, wholeThyroid Diseases genome screening using microsatellites yielded evidence for the existence of other Little is known concerning the susceptisusceptibility loci, including IDDM-3 bility genes for AITD; however, epidemi(15q26), IDDM-4 (llq13), IDDM-5 (6q), ological evidence for a genetic susceptiIDDM-6 (18q), IDDM 7 (2q31), and more bility to AITD is abundant. (Julieret al. 1991,Davieset al. 1994,Todd 1995). Furthermore, the combination of Twin Studies such genes, for example within HLA-susceptible populations, greatly increased In the largest twin study of Graves’ distheir evidence for linkage (Aitman and ease, performed in Denmark, the conTodd 1995). These data indicate that the cordance rate for MZ twins was 76Y0(16 genetic susceptibilityto IDDM is probably of 21), and for DZ twins, the concorinfluenced by shared allelesat severalun- dance rate was 11% (4 of 37) (Harvald linked loci across the genome. The identi- and Hauge 1956). There have also been fication of the responsible genes at these reports of monozygotic twins with Hashloci remains a major challenge for inves- imoto’s disease (Irvine et al. 1961), identical triplets with Hashimoto’s disease tigators at this time. (McGregor et al. 1979), and monozygotic twins in whom one twin was affected by Graves’ disease and the other, ● The Autoimmune by Hashimoto’s disease (Chertow et al. Thyroid Diseases 1973). Thus, the twin studies indicate The AITDs are autoimmune disorders that genetic predisposition plays a major characterized by abnormalities of thy- role in the pathogenesis of AITD. TEM vol. 8, No. 2, 1997

Studiesof Relativesof Patients with Autoimmune Thyroid Diseases The familial occurrence of AITD has been recognized by several investigators for many years.Bartels(1941) found evidence of a familial predisposition in 609ioof cases with Graves’ disease. Martin (1945) found that 22V0of patients with Graves’ disease had first-degree relatives with Graves’disease. Moreover, severalthyroid abnormalities have been reported in relatives of patients with AITD (Tamai et al. 1980, Chopra et al. 1977, Tamai et al. 1986). The most common abnormalities were the presence of thyroid autoantibodies reported in up to 50% of the siblingsof patients with AITD (Hall et al. 1960, Hall and Stanbury 1967, Chopra et al. 1977, Burek et al. 1982, Volp6 R. 1985). In a large study from Japan of 206 euthyroid individuals with a family history of Graves’disease,20.7% were found to have Tg antibodies, and 55.2V0had thyroid peroxidase (microsomal) antibodies (Tamai et al. 1986). These data suggest a hereditary influence on the production of antithyroidal antibodies, and the presence of thyroid antibodies in 50% of siblings and children of patientsis suggestiveof a dominant form of inheritance (Hall and Stanbury 1967). Human LeukocyteAntigen Association Studies in Autoimmune Thyroid Diseases Graves’ disease was initially found to be associated with HLA-B8 in Caucasians (Bech et al. 1977). Subsequently it was found that Graves’ disease was more strongly associated with DR3, which is now known to be in linkage disequilibrium with HLA-B8 (Farid et al. 1979, Mangklabruks et al. 1991). The frequency of DR3 in Graves’ disease patients is 56?40and in the general population, 26?40,with a relative risk for people with HLA-DR3 of 3.7 (Mangklabruks et al. 1991). Even though the frequency of HLA-DR3 is increased in Caucasians with Graves’ disease, the HLA associations are different in other ethnic groups. In the Japanese population, Graves’ disease was associated with HLA-B35 (Kawa et al. 1977), and in the Chinese population, an increased frequency of HLA-Bw46 was reported (Chan et al. 1978). Among Caucasians, HLA-DQA1*0501 has recently been described as conferring a risk for Graves’

PIIS1043-276O(96)OO266-4 Q 1997,EkevierScienceInc., 1043-2760/97/$17.00

67

disease that may be over and above that of HLA-DR3 (relative risk 3.8) (Barlow et al. 1996, Yanagawa et al. 1993). Recently, a disease susceptibility–extended haplotype has been described for Graves’ disease (Ratanachaiyavong et al. 1993). It is interesting to note that the risk of HLAidentical siblings developing Graves’ disease was only 7°/0,which is much lower than the concordance for MZ twins (Stenszky et al. 1985). Therefore, we can conclude that the HLA haplotypes associated with Graves’ disease are not necessary disease genes, as observed for IDDM, but merely confer increased risk for the development of the disease. HLA associations have been reported in Hashimoto’s disease as well, albeit the associations were weaker than in Graves’ disease. Hashimoto’s disease was found to be associated in Caucasians with HLA-DR5, with a relative risk of up to 4.2 (Farid et al. 1981, Weissel et al. 1980). In other studies in Caucasians, Hashimoto’s disease was found to be associated with HLA-DR4 (Farid 1987) and HLA-DR3 (Tandon et al. 1991). Recently, an association was reported between Hashimoto’s disease and HLADQw7 (DQB1 ‘0301), with a relative risk of 4.7 (Wu et al. 1994, Badenhoop et al. 1990). Other associations of Hashimoto’s disease with HLA have also been reported in other populations, for example, HLA-DRw53 in Japanese and HLADR9 in Chinese [for a review, see Weetman (1991)]. Other Markers Studiedfor Association with Autoimmune Thyroid Diseases Recognizing that the genes important for the development of AITD are not located within the HLA region, several investigators have recently begun studying other candidate genes in patients with AITD. One of the first studied genes was the IgG heavy chain gene (IgH). Several studies found associations between IgG heavy chain Gm allotypes and Graves’ disease in the Japanese population (Nakao et al. 1980). A T-cell receptor (3chain polymorphism was reported to be associated with Hashimoto’s disease (Ito et al. 1989) and Graves’ disease (Demaine et al. 1987), but this could not be confirmed (Mangldabruks et al. 1991). Tassi and colleagues (Pirro et al. 1995) have shown no association between AITD and a microsatellite marker inside the TPO gene, despite the important role that

68

TPO plays as a thyroid autoantigen. The same workers demonstrated an association between a polymorphic allele localized in the thyroid hormone &receptor gene and Graves’ disease (Tassi et al. 1995). Recently several reports have demonstrated that the CTLA-4 gene, which is known to be in linkage disequilibrium with the CD28 gene, is associated with Graves’ disease, with a relative risk of 2.82 (Yanagawa et al. 1995). A polymorphism at the extracellular domain of the TSH receptor (TSHR) in codon 52 (coding for either threonine of proline) was recently described (Bohr 1993), but despite an early report of an association between this polymorphism and Graves’ orbitopathy (Bahn et al. 1994), later studies demonstrated no association (Ahmad et al. 1994, Watson et al. 1995).

Linkage Studies in Autoimmune Thyroid Diseases In contrast to the many association studies, only a few linkage studies have been performed in AITD to date, mostly investigating the HLA genes. Although the first study suggested linkage of Graves’ disease to the HLA gene region using sib-pair analysis (Payami et al. 1989), we and others showed no linkage between AITD and HLA genes using classic analytical techniques (O’Connor et al. 1993, Roman et al. 1992, Shields et al. 1994). Therefore, it seems that although certain HLA genes confer an increased risk of developing AITD, as evidenced by their association with AITD, such genes only confer a modulating influence on disease development. Prentice et al. (1993) have tested for linkage between thyroid autoantibodies and several candidate genes, including the IgH gene, TCR-a gene, the IDDM 1lq gene, and microsatellites on chromosome 21 (examined because of the association between AITD and Down’s syndrome). These workers failed to find linkage of thyroid autoantibody expression to any of these candidate genes.

●

Summary

It is clear that autoimmune diseases have major genetic components. Genes may influence disease in two distinct ways. They may be essential for disease development so that they must be present in the genome for the disease to

occur. The regions of the genome containing such genes are “linked” to the disease. The second type of genes are those that are not essential for disease development, but if present, increase or decrease the susceptibility of the individual to develop the disease. Such genes are “associated” with the disease. Data are now rapidly accumulating concerning the characteristics of a variety of susceptibility genes in IDDM and AITD. To date, such genes appear to be largely distinct, although data on CTLA-4 suggest that it may be the first common susceptibility gene between IDDM and AITD. Today,we can begin to predict the onset of IDDM in children of patients with IDDM, and tomorrow, a similar approach may be possible in AITD. However, the pathophysiologic functions of the non-HLA related genes, such as the insulin gene, which are being identified as important in disease susceptibility, remain to be discovered.

●

Acknowledgment

This work supported in part by NIDDKD grants DK35764 andDK45011 (to T.F.D.), the David Owen Segaf Endowment (to Y.T.),the Universityof Pisa (to G.B.), and grantsNS27941 and DK31775 (to D.A.G.).

References Ahmad MF, Stenszky V, Juhasz F, Balazs G, Farid NR: 1994. No mutations in the translated region of exon 1 in the TSH receptor in Graves’thyroid glands. Thyroid 4:151-153. Aitman TJ, Todd JA: 1995. Molecular genetics of diabetes mellitus. Bailli&es Clin Endocrinol Metab 9:631+56. Badenhoop K, Schwartz G, Walfish PG, et al.: 1990. Susceptibility to thyroid autoimmune disease: molecular analysis of HLA-D region genes identifies new markers for goitrous Hashimoto’s thyroiditis. J Clin Endocrinol Metab 71:1131–1137. Bahn RS, Dutton CM, Heufelder AE, SarkarG: 1994.A genomic point mutation in the extracellular domain of the TSH receptor in patients with Graves’ ophthalmopathy. J Clin Endocrin Metab 78:256-260. Bain SC, Prins JB, Heame CM, et al.: 1992. Insulin gene region-encoded susceptibilityto type 1 diabetes is not restrictedto HLA-DR4positive individuals. Nat Genet 2:212-215. Barlow ABT,Wheatcroft N, Watson P,Weetman AP: 1996. Association of HLA-DQA1*-0501 with Graves’ disease in English Caucasian

@ 1997,ElsevierScienceInc., 1043-2760/97/$17.00 PIIS1043-276O(96)OO266-4

TEM vol.8, No. 2, 1997

men and women. Clin Endocrinol (Oxf) 44: 73-77.

The Thyroid: A Fundamental Text, 7th ed, Phiiadeiphia, Lippincott-Raven,pp 525-536

BarnettAH, Eff C, Leslie RDG, Pyke DA: 1981. Diabetes in identicaf twins: a study of 200 pairs. Diabetologia 20:87-93.

DaviesJL, Kawauchi Y, Bennet ST,et aL: 1994. A genome-wide search for human type 1 diabetes susceptibility genes. Nature 371:13& 136.

“lto M, ‘“ -lammoto M, ‘- ‘‘ ‘1989. --Kamura ‘H, et al.: Association of HLA antigen and restriction fragment length polymorphism of T cell receptor beta-chain gene with Graves’ disease and Hashimoto’s thyroiditis. J Clin Endocrinol Metab 69:1OG1O4.

Demaine AA, Welsh KI, Hawe BS, Farid NR: 1987. Polymorphism of the T cell receptor beta-chain in Graves’ disease. J Clin Endocrinol Metab 65:643–646.

JulierC, Hyer RN, DaviesJ, et af.: 1991. Insulin1GF2region on chromosome 1lp encodes a gene implicated in HLA-DR4-dependentdiabetes susceptibility.Nature 354:155-159.

Docherty K: 1992. The regulation of insulin gene expression. Diabet Med 9:792-798.

Kawa A, Nakamura S, Nakazawa M, Sakaguch S, Kawabata T, Masda Y, Kanehisa T: 1977. HLA-BW35 and B5 in Japanesepatientswith Graves’ disease. Acta Endocnnol (Copenh) 86:754-757.

BartelsED: 1941. TwinExaminations: Heredity in Graves’ Disease. Copenhagen, Munksgaard, pp 32-36. Bech K, Lumholtz B, Nerup J, et aL: 1977. HLA antigens in Graves’disease. Acta Endocrinol (Copenh) 86:510-516. Bell GI, Horita S, Karam JH: 1984. A polymorphic locus near the human insulin gene is associated with insulin-dependent diabetes mellitus. Diabetes 33:17ti183. Bennett PH, Rushforth NB, Miller M, et af.: 1976. Epidemiologic studies of diabetes in the Pima Indians. Recent Prog Horm Res 32:333-376. Bennett ST, Lucassen AM, Gough SCL, et al.: 1995. Susceptibilityto human type 1 diabetes at IDDM2 is determined by tandem repeat variation at the insulin gene minisatellitelocus. Nat Genet 9:284–292. Bohr URM: 1993, A heritablepoint mutation in an extracellulardomain of the TSH receptor involved in the interaction with Graves’ disease. Biochim Biophys Acta 1216:504–508. Botazzo GF: 1984. Beta-celldamage in diabetic insulitis: are we approaching a solution? Diabetologia 26:241–249. Bougneres PF,Carel JC, Castino L, et al.: 1982. Factors associated with early remission of type 1 diabetes in children treated with cyclosporine. N Engl J Med 306:785–788. Brown JH, JardetzkyT, Gofga J: 1993. Threedimensional structure of the human class II histocompatibility antigen HLA-DR1.Nature 364:33-39. Burek CL, Hoffman WH, Rose NR: 1982. The presence of thyroid autoantibodies in children and adolescents with AITD and in their siblings and parents.ClinImmunol Immunopathol 25:395404. Cahill GFJ, McDevitt HO: 1981. Insulin-dependent diabetes mellitus: the initiaf lesion. N Engl J Med 304:1454-1465. Chan SH, Yeo PP,Lui KF,et al.: 1978. HLA and thyrotoxicosis (Graves’ disease) in Chinese. Tissue Antigens 12:109-114. Chertow BS, Fidler WJ, Fariss BL: 1973. Graves’ disease and Hashimoto’s thyroiditis in monozygotic twins. Acta Endocrinol (Copenh) 72:18-24. Chopra IJ, Solomon DH, Chopra U, Yodhihara E, TersakiPL, Smith F: 1977. Abnormalities in thyroid function in relatives of patients with Graves’ disease and Hashimoto’s thyroiditis: lack of correlation with inheritance of HLA-B8. J Clin Endocrinol Metab 45:45-54. Davies TF: 1996. The pathogenesis of Graves’ disease. In Bravennan LE, Utiger RD, eds.

TEM Vol.8, No. 2, 1997

Falk CT,Rubinstein P: 1987. Haplotype relative risks: an easy and reliable way to construct a proper control sample for risk calculations. Am J Hum Genet 51:227-233. Falorni A, Kockum CB, SanjeeviCB, Lemmark A: 1995. The pathogenesis of insulin-dependent diabetes mellitus. Bailli&es Clin Endocrinol Metab 9:25+6. Farid NR: 1987. Immunogenetics of autoimmune thyroid disorders. Endocrinol Metab Clin North Am 16:229–245. Farid NR, Sampson L, Noel EP, et af.: 1979. A study of human D. locus related antigens in Graves’disease. J Clin Invest 63:108-1 13. Farid NR, Sampson L, Moens H, Barnard JM: 1981. The association of goitrous autoimmune thyroiditis with HLA-DR5. Tissue Antigens 17:265–268. FreedmanBI, TuttleAB, SprayBJ: 1995.Familial predisposition to nephropathy in AfricanAmericans with non–insulin-dependent diabetes mellitus. Am J Kidney Dis 25:710-713. Gamble DR: 1980. The epidemiology of indulin dependentdiabetes,with particularreference to the relationship of virus infection to its etiology Epidemiol Rev 2:49–70. Greenberg DA: 1993. Linkage analysis of “necessary”loci versus “susceptibility”loci. Am J Med Genet 2:135-143. Hall R, Stanbury JB: 1967. Familial studies of autoimmune thyroiditis. Clin Exp Immunol 2:719-725.

Kennedy GC, German MS, Rutter WJ: 1995. The minisatellite in the diabetes susceptibility locus IDDM2 regulates insulin transcription. Nat Genet 9:293–298. Knapp M, Seucher SA, Baur MP: 1994. Linkage analysis in nuclear families. II. Relationship between affected sib-pair tests and lod score anafysis. Hum Hered 44:44–51. Kockum I, Wassmuth R, Holmberg E, et al.: 1993. HL&DQ protection and HLA-DR susceptibility in Type 1 (insulin-dependent) diabetes studied in population-based affected families and controls. Am J Hum Genet 42: 15&167. LaPorte RE, Fishbein HA, Drash AL, et aL: 1981. The Pittsburgh insulin-dependent diabetes mellitus (IDDM) registry:the incidence of insulin-dependent diabetes mellitus in AIlegheny County, Pennsylvania (1965-1976). Diabetes 30:279-284. Levine SN: 1983. Currentconcepts of thyroiditis. Arch Intern Med 143:1952–1956. Lucassen AM, Julier C, Beressi JP,et aL: 1993. Susceptibility to insulin dependent diabetes mellitus maps to a 4.1 kb segment of DNA spanning the insulin gene and associated VNTR. Nat Genet 4:305–310.

Hall R, Owen SG, SmartGA: 1960.Evidencefor genetic predisposition to formation of thyroid autoantibodies. Lancet 2:187–190.

MangkfabruksA, Cox N, DeGroot LJ: 1991. Genetic factors in autoimmune thyroid disease analyzed by restrictionfragmentlength polymorphisms of candidate genes. J Clin Endocrinol Metab 73:236–244.

Harvald B, Hauge M: 1956. A catamnestic investigation of Danish twins. Dan Med Bull 3:15&158.

Martin L: 1945. The heredity and familiaf aspects of exophthalmic goitre and nodular goitre. Q J Med 14:207–219.

Hashimoto L, Habita C, BeresslJB, et al.: 1994. Genetic mapping of a susceptibilitylocus for insulin-dependentdiabetes mellitus on chromosome 1lq. Nature 371:161 –164.

McDougall R: 1991. Graves’ disease: current concepts. Med Clin North Am 75:79–95. McGregor AG, Roberts DF, Hall R: 1979. A studyof tripletswith Hashimoto’s thyroiditis. Postgrad Med J 55:894-896.

Hawkins BR, Cheah PS, Burger HG, Patel Y, MacKay IR, Welborn TA: 1980. Diagnostic significance of thyroid microsomaf antibodies in a randomly selectedpopulation. Lancet 2:1057-1059.

Nakao Y,Matsumoto H, MiyazakiT,et af.: 1980. IgG heavy chain alfotypes (Gin) in atrophic and goitrous thyroiditis. Clin Exp Immunol 42:2C26.

Irvine WJ, McGregor AG, StuartAE, Hall GH: 1961. Hashimoto’s disease in uniowdar twins. Lancet 2:850853.

Nelson JL, Hansen JA: 1990. Autoimmune disease and HLA. CRC Crit Rev Immunol 10: 307-328.

G 1997,ElsevierScienceInc., 1043-2760/97/$17.00 PIIS1043-276O(96)OO266-4

69

Nerup J, Mandnup-Poulsen T, Molvig J: 1987. The HLA-IDDMassociation: implications for etiology and pathogenesis of IDDM. Diabetes Metab Rev 3:779-802. O’Connor G, Neafeld DS, Greenberg DA, Conception L, Roman SH, DaviesTF: 1993. Lack of disease associated HLA-DQ restriction fragment length polymorphisms in famifies with autoimmune thyroid disease. Autoimmunity 14:237–241. Ott J: 1996. Analysis of Human Genetic Link age. Baftimore, Johns Hopkins University Press. Payami H, Joe S, Farid NR, et al.: 1989.Relative predispositionaf effectsof markeralleleswith disease: HLA-DR alleles and Graves’disease. Am J Hum Genet 45:541-546. Phillips DIW, Prentice L, McLachlan SM, Upadhyaya M, Lunt PW, Rees Smith B: 1991. Autosomal dominant inheritance of the tendency to develop thyroid autoantibodies. Exp Clin Endocrinol 97:17L172. Pirro MT,De Filippis V,Di CerbnA, ScillitaniA, Liuzzi A, Tassi V: 1995. Thyroperoxidase microsatellitepolymorphism in thyroid disease. Thyroid 5:461464. Prentice L, Phillips DfW, Premawardhana LDKE, Rees Smith B: 1993. Genetic linkage analysis of thyroid autoantibodies. Autoimmunity 15:225–229. RatanachaiyavongS, Lloyd L, DarkeC, McGregor AM: 1993. MHC-extended haplotypes in families of patients with Graves’ disease. Hum Immunol 36:99-1 11. Rich SS, Green A, Morton NE, et af.: 1987. A combined segregationand linkageanalysisof insulin-dependent diabetes mellitus. Am J Hum Genet 40:237-249. Roman SH, Greenberg DA, Rubinstein P,WaL lenstein S, Davies TF: 1992. Genetics of autoimmune thyroid disease: lack of evidence for linkage to HLA within families. J Clin Endocrinol Metab 74:496-503. Shields DC, Ratanachaiyavong S, McGregor AM, Collins A, Morton NE: 1994. Combined segregation and linkage analysis of Graves’ diseasewith a thyroid antibody diathesis.Am J Hum Gen 55:540-554. Singal DP,Blajchman MA: 1973. Histocompatibility (HL-A) antigens, lymphocytotoxic antibodies and tissue antibodies in patients with diabetes mellitus. Diabetes 22:429432.

the insulin gene region and insulin dependent diabetes melfitus.Am J Hum Genet 52: 506516.

1993. 5’ insulin gene polymorphism confers risks to IDDM independentfyof HLA class II susceptibility.Diabetes 42:851–854.

Stenszky V, Kozma L, Bafazs C, Rochlitz S, Bear JC, Farid NR: 1985. The genetics of Graves’disease:HLA and disease susceptibility.J Clin Endocrinol Metab 61:735–740.

Vanderpump MPJ, Tunbridge WMG, French JM, et al.: 1995. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham survey.Clin Endocrinol (Oxf) 43:5548.

Tamai H, Ohsako N, Takeno K, et al.: 1980. Changes in thyroid function in euthyroid subjects with family history of Graves’ disease: a follow-up study of 69 patients. J Clin Endocrinol Metab 51:1123-1128. Tamai H, KumagaiLF,NagatakiS: 1986.Immunogenetics of Graves’ disease. In McGregor AM, ed. Immunology of Endocrine Diseases. hmaste~ UK, MTP Press,pp 123-141. Tandon N, Zhang L, Weetman AP: 1991. HLA associations with Hashimoto’s thyroiditis. Clin Endocrinol 34:383-386. TassiY Scamecchia L, Di Cerbo A, et al.: 1995. A thyroid hormone receptor beta gene polymorphism associated with Graves’disease. J Mol Endocnnol 15:267-272. Tattersal RB, Fajans SS: 1975. A difference between the inheritance of classical iuvenileonset and maturity-onset type diabetes of young people. Diabetes 24:44-53. TattersallRB, Pyke DA: 1972. Diabetes in identical twins. Lancet 2:1120–1125. Todd JA: 1995. Genetic analysis of type 1 diabetes using whole genome approaches. Proc Natf Acad Sci USA 92:856@8565. Todd JA. Bell JL McDevittHO: 1987. HLA-DQbeta gene contributes to susceptibility and resistanceto insulin-dependentdiabetes mellitus. Nature 329:599-604. Todd JA, Aitman TJ, Comall RJ, et aL: 1991. Genetic analysis of autoimmune type 1 diabetes mellitus in mice. Nature 351:542-547. Tomer Y, Davies TF: 1995. Infections and autoimmune endocrine disease. Bailli?res Clin Endocrinol Metab 9:47-70. Torfs CP,King M, Bing H, MalmgrenJ, Grumet FC: 1986. Genetic interrelationshipbetween insulin-dependent diabetes mellitus, the autoimmune thyroid diseases, and rheumatoid arthritis.Am J Hum Genet 38:170-187. Tunbridge WMG, Evered DC, Half R, et aL: 1977. The spectrum of thyroid disease in a community: the Whickham survey.Clin Endocrinol (Oxf) 7:481493.

Spielman RS, Baker L, Zmijewski CM: 1980 Gene dosage and susceptibilityto insulindependentdiabetes.Ann Hum Genet44:135-150.

Undlien DE, Bennet ST, Todd JA, et al.: 1995. Insufin gene region-encoded susceptibilityto IDDM maps upstream of the insulin gene. Diabetes 44:620425.

Spielman RS, McGinnis RE, Ewens WJ: 1993. Transmission test for linkage disequilibrium:

Van der Auwera B, Heimberg H, SchrevensAF, Van Wayenberge C, Fkunent J, Schuit FC:

70

Volpe R: 1985. Autoimmune thyroid disease.In VolpeR, ed.AutoirnmunitvandEndocrineDisease.New York,Marcel DekkeLpp 109–255. Wagener DK, Sacks JM, LaPorte RE, MacGregor JM: 1982. The Pittsburgh study of insulin-dependent diabetes mellitus: risk for diabetes among relativesof IDDM. Diabetes 31: 136-144. Warram JH, Krolewski AS, Gottlieb MS, Kahn CR: 1984. Differences in risk of insulin-dependent diabetes in offspring of diabetic mothers and diabetic fathem. N Engl J Med 311:149-152. Watson PF, French A, Pickerill AP, McIntosh RS, Weetman AP: 1995. Lack of association between a polymorphism in the coding region of the thyrotropin receptor gene and Graves’disease. J Clin Endocrinol Metab 80: 1032-1035. Weber JL: 1990. Human DNA polymorphisms based on lengthvariationsin simple-sequence tandemrepeats.Genome Anaf 1:159–181. Weetman AP: 1991. Autoimmune Endocrine Disease. Cambridge, Cambridge University Press. Weetman AP, McGregor AM: 1984. Autoimmune thyroid disease: developments in our understanding. Endocr Rev 5:309–355. Weissel M, Hofer R, Zasmeta H, Mayr WR: 1980. HLA-DR and Hashimoto’s thyroiditis. TissueAntigens 16:256259. West KM: 1978. Epidemiology of Diabetes and Its Vascular Lesions. New York, Elsevier. Wu Z, Stephens HAF, Sachs JA, et af.: 1994. Molecukwanalysis of HLA-DQand -DP genes in Caucasoid patients with Hashimoto’s thyroiditis. Tissue Antigens43: 116–119. YanagawaT, MangklabruksA, Chang YB, et aL: 1993. Human histocompatibility leukocyte antigen-DQAl*0501 allele associated with genetic susceptibility to Graves’ disease in a Caucasian population. J Clin Endocrinol Metab 76:1569-1574. Yanagawa T, Hidaka Y, Guimaraes V, Soliman M, DeGroot LJ: 1995. CTLA-4gene po&rnorphism associated with Graves’ disease in a Caucasian population. J Clin Endocrinol TEM Metab 80:41-45.

@ 1997,ElsevierScienceInc., 1043-2760/97/$17.00 PIIS1043-276O(96)OO266-4

TEM vol.8, No. 2, 1997