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The significance of human leukocyte antigen profiles in human infertility, recurrent abortion, and pregnancy disorders
FERTILITY AND STERILITY Copyright" 1985 The American Fertility Society
Vol. 43, No.5, May 1985 Printed in U.8A.
The significance of human leukocyte antigen profiles in human infertility, recurrent abortion, and pregnancy disorders
Alan C. Menge, Ph.D. *
Alan E. Beer, M.D. Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan
Received March 13, 1985. *Reprint requests: Alan C. Menge, Ph.D., Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan 48109. Vol. 43, No.5, May 1985
Over the past 5 years there have been numerous articles addressing the influence of the major histocompatibility complex (MHC) on fertility and reproductive outcome. In this issue of Fertility and Sterility, the contribution by Persitz et al. l onhistoincompatibility in couples with unexplained infertility concludes that there is no significant difference in the frequency or shaing of human leukocyte antigens (HLAs) between infertile and fertile couples. The purpose of this editorial is to present for the clinician and clinician scientist a position statement that will be helpful as patients present with unexplained infertility, recurrent abortion, or disorders of pregnancy. The MHC in humans is a region on chromosome 6 consisting of a series of genes that code for cell surface expression of strong transplantation antigens. This system, called HLA, is composed of two types of transplantation antigens, class I and class II. The general function of the class I gene products is to serve as determinants necessary for immune recognition and elimination of virally infected cells and as targets in graft rejection; whereas the class II molecules are involved in immune responses through cell-to-cell interactions and cooperation among immune cells, graft rejection, and possibly graft-versus-host disease. The occurrence of certain HLA antigens has been associated with susceptibility to some diseases involving the immune and endocrine systems and autoimmunity, although the mechanisms are not well understood. The lack of an association between HLA antigens and unexplained infertility, as reported by Persitz et al. l 'in Israeli couples, also was noted earlier by Nordlander et al. 2 among couples of Scandinavian origin. Failure to observe a direct relationship is not unexpected, because the cause of the infertility may be diverse, and the numbers of observations were small. The occurrence of antisperm antibodies, however, has reportedly been related to the expression of certain HLA-B antigens and antibodies against some HLA antigens. a This study needs expansion, and confirmation for it and studies on HLA expression on human sperm cells are areas of controversy. The literature reveals studies that find no evidence of HLA antigens to those reporting multiple antigens of class I and II types on sperm. A recent study by Anderson et al.,4 using a panel of monoclonal antibodies, failed to detect HLA-A, -B, -C, -DR or 132microglobulin on postmeiotic germ cells of testes or on sperm cells from the epididymides and ejaculates of men. Also, the contention Menge and Beer Editor's corner
693
that common antigens exist between sperm and lymphocytes is questioned in light of results of Beer and co-workers,5 in which the induction or anamnestic response of antisperm antibodies did not occur in women given injections of their husbands' lymphocytes. While sperm and leukocytes may share antigens, most, if not all, are probably species-specific. The lack of HLA antigens on sperm cells may account for the low incidence of cell-mediated autoimmune orchitis in man and the low association of infertility with measures of cell-mediated immunity. Thus, while sperm may not express HLA, the ejaculate usually contains other nucleated cells possessing HLA antigens (Le., leukocytes, epithelial cells) which under some conditions may sensitize the female partner against incompatible HLA antigens. Likewise, microbial and viral infections of the male reproductive tract may trigger leukocyte release of secretions capable of stimulating or potentiating immune responses in the male or female reproductive tract. Interferon-), is known to induce Ia expression in nonexpressing or poorly expressing cells, which in turn allows these cells to participate in antigen (sperm?, HLA?) processing and immune cell cooperation, initiating or promoting an immune response. A question still to be an_swered and relevant to the following section is whether or not the ejaculate normally sensitizes the female against antigens that would be expressed by a developing conceptus. Progress in our understanding of the critical features of the placental trophoblast for immune protection in the mother has burgeoned during the past 5 years.6 It can be stated with certainty that these critical features of the trophoblast are (1) resisting destruction by cytotoxic lymphocytes and antibodies; (2) forming a physical barrier to immune effector cells but not antibody, prohibiting them from reaching the fetus; (3) signaling the migration of suppressor or other functionally hyporesponsive lymphocytes to the uterine decidual and uterine lymphatics; (4) promoting the production of maternal serum mixed lymphocyte culture (MLC) blocking antibody with paternal specificity; (5) establishing receptors on its membrane which bind to agents in maternal plasma (Le., transferrin, epithelial growth factor, which have both transport and immunodirective function); (6) producing protein and steroid hormones in high local concentrations that have immunoregulatory .functions as well as regulating gene expression of cells at the maternal-fetal tissue 694
Menge ~d Beer Editor's corner
l
interface; and (7) sustaining the production of blocking antibodies that bind on a paternal-antigen-specific basis to its membrane. The question currently facing clinicians is whether HLA antigen screening and other immunologic screening6 identifies couples whose infertility, pregnancy wastage, or poor pregnancy performance is due to the failure of the trophoblast to perform in a timely manner these critical functions for immune protection in the mother, or is due to immunodeviation of their responses along cytotoxic lines that interfere with sperm function or viability or to responses that are cytotoxic to the preimplantation embryo. Unlike what has been reported in inbred strains of mice, mating in humans appears to be a random event, in that HLA antigen profiles between spouses do not vary from the expected. Also, the expected HLA antigen frequency between computer-mated individuals does not differ in any respect from the observed frequency in couples studied in Switzerland. 7 Many couples with recurrent abortions of unknown etiology, however, share significantly more HLA-B, -DR, and -MT locus antigens than control couples. 6 In addition, the following observations in aborting couples have been made: (1) HLA antigen frequency in the aborting group is comparable to that of fertile control subjects or of American Caucasians. (2) Aborting women do not show any differences in distribution of ABO blood types from those of fertile couples or those of couples tested for paternity determination. (3) The incidence of antisperm antibodies is not significantly elevated in this group. (4) Immunotherapy of aborting women with paternal leukocytes will sustain a subsequent pregnancy to term in those developing blocking factors in MLC, whereas in those women lacking the blocking factors abortions recur. (5) In over 300 couples evaluated, no woman positive for agglutinating and immobilizing sperm antibodies and also a recurrent aborter of unknown etiology has delivered a live-born infant. Support for the influence of HLA on fertility is provided by a prospective study in Hutterites by Ober et al. 8 that showed a marked decrease in fertility in couples sharing HLA-DR antigens. In a related study, they found an increased sex ratio among HLA-DR-compatible pregnancies in the same population. They postulate that the mechanism is that the H-Y antigen of male fetuses may compensate compatible pregnancies by providing
Fertility and Sterility
a sufficient antigenic stimulus to elicit a normal maternal immunologic response. 9 Immunologic concerns regarding immunotherapy of women with paternal leukocytes have arisen. Three of 2& women with three or more recurrent abortions who shared HLA antigens with their spouses and were found to lack some ofthose critical features of the trophoblast for immune protection in the mother were immunized with paternal leukocytes and became pregnant. All three experienced severe intrauterine growth retardation, evident by 22 weeks of pregnancy. In addition, parental HLA compatibility or compatibility at a locus near to HLA-A region in these couples may predispose them to produce children with anencephaly and other neural tube defects.!O In the same vein, there are reports that antigens of the HLA system may be involved in determining which genetically abnormal human infants are aborted and which are gestated to term. 11 In summary, we agree with Persitz and coworkers! that HLA antigen screening in individuals with primary infertility has not proven helpful; however, immunologic screening, including HLA typing of couples with recurrent abortions or anomalies of pregnancy, is beneficial and should be part of the workup in a case of infertility. Immunologic analyses evaluating maternal systemic responses as well as uterine decidual lymphoid cell responses to paternal alloantigens not routine in some laboratories can definitely identifY women who are abortion-prone after a full medical workup and in addition can identify those in whom immunotherapy may be dangerous, in that it may pass a problem on to the fetus (intrauterine growth retardation, neonatal acquired immune deficiency syndrome secondary to graft-versus-host disease, or placing the couple at risk of bearing a genetically abnormal child). Finally, immunologic screening has progressed to an art wherein aborting couples with no cause for their abortions can know whether altered immunologic responses underly their problem. HLA testing, in the minds of most experts, will identifY most, but not all, couples with reproductive failure, i.e., recurrent abortions. Prospective
Vol. 43, No.5, May 1985
studies indicate that HLA antigen sharing may identify couples who share other chromosomal material closely linked to HLA: a growth and reproduction locus similar to the Tit locus in the mouse, where mates homozygous for this locus experience reproductive inefficiency, fetuses with multiple anomalies, and primary infertility.!O In addition, couples sharing antigens at this locus may fail to initiate the protective immune responses or deviate them along lines cytotoxic or damaging to the fetoplacental unit. REFERENCES 1. Persitz E, Oksenberg JR, Margalioth EJ, Hacohen S, Schenker J, Brautbar C: Histoincompatibility in couples with unexplained infertility. Fertil Steril 43:733, 1985 2. Nordlander C, Fuchs T, Hammarstrom L, Smith CIE: Human leukocyte antigens group A in couples with unexplained infertility. Fertil Steril 40:60, 1983 3. Genco PV, Mathur S, Williamson HO, Rust PF, Glassman AB, Fudenberg HH: Antibodies to A19 and Bw35 com~ plexes of human leukocyte antigens are present in infertile subjects with sperm antibodies. Fertil Steril 42:554, 1984 4. Anderson DJ, Narayan P, DeWolf WC: Major histocompatibility antigens are not detectable on postmeiotic human testicular germ cells. J ImmunoI133:1962, 1984 5. Beer AE, Quebbeman JF, Semprini AE: Immunopathological factors contributing to recurrent spontaneous abortions in humans. In Spontaneous Abortions, Edited by ESE Hafez, DK Edmonds. London, Blackwell Scientific Publishers, 1985. In press 6. Beer AE, Semprini AE, Xiaoyu Z, Quebbeman JF: Pregnancy outcome in human couples with recurrent spontaneous abortions. Exp Clin Immunogenet. In press, 1985 7. Bischof P, Jeannet M, Bourrit B, Vuagnat P, Herrman WL, Sizonenko PC: Mating is random. Am J Reprod Immunol. In press, 1985 8. Ober CL, Hauck WW, Kostyu DD, O'Brien E, Elias S, Simpson JL, Martin AO: Adverse effects ofHLA-DR sharing on fertility: a cohort study in a human isolate. Fertil Steril. Submitted for publication 9. Ober CL, Simpson JL, Radvany R: Increased sex ratios among HLA-DR compatible pregnancies. Lancet. In press, 1985 10. Schacter B, Weitkamp LR, Johnson WE: Parental HLA compatibility, fetal wastage and neural tube defects: evidence for a TIt like locus in humans. Am J Hum Genet 36:1082,1984 11. Mottironi VD, Hook EB, Willey AM, Porter IH, Swift RV, Hatcher NH: Decreased HLA heterogenicity in parents of children with Down Syndrome. Am J Hum Genet 35: 1289, 1983
Menge and Beer Editor's corner
695
Vol. 43, No.5, May 1985 Printed in U.8A.
The significance of human leukocyte antigen profiles in human infertility, recurrent abortion, and pregnancy disorders
Alan C. Menge, Ph.D. *
Alan E. Beer, M.D. Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan
Received March 13, 1985. *Reprint requests: Alan C. Menge, Ph.D., Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, Michigan 48109. Vol. 43, No.5, May 1985
Over the past 5 years there have been numerous articles addressing the influence of the major histocompatibility complex (MHC) on fertility and reproductive outcome. In this issue of Fertility and Sterility, the contribution by Persitz et al. l onhistoincompatibility in couples with unexplained infertility concludes that there is no significant difference in the frequency or shaing of human leukocyte antigens (HLAs) between infertile and fertile couples. The purpose of this editorial is to present for the clinician and clinician scientist a position statement that will be helpful as patients present with unexplained infertility, recurrent abortion, or disorders of pregnancy. The MHC in humans is a region on chromosome 6 consisting of a series of genes that code for cell surface expression of strong transplantation antigens. This system, called HLA, is composed of two types of transplantation antigens, class I and class II. The general function of the class I gene products is to serve as determinants necessary for immune recognition and elimination of virally infected cells and as targets in graft rejection; whereas the class II molecules are involved in immune responses through cell-to-cell interactions and cooperation among immune cells, graft rejection, and possibly graft-versus-host disease. The occurrence of certain HLA antigens has been associated with susceptibility to some diseases involving the immune and endocrine systems and autoimmunity, although the mechanisms are not well understood. The lack of an association between HLA antigens and unexplained infertility, as reported by Persitz et al. l 'in Israeli couples, also was noted earlier by Nordlander et al. 2 among couples of Scandinavian origin. Failure to observe a direct relationship is not unexpected, because the cause of the infertility may be diverse, and the numbers of observations were small. The occurrence of antisperm antibodies, however, has reportedly been related to the expression of certain HLA-B antigens and antibodies against some HLA antigens. a This study needs expansion, and confirmation for it and studies on HLA expression on human sperm cells are areas of controversy. The literature reveals studies that find no evidence of HLA antigens to those reporting multiple antigens of class I and II types on sperm. A recent study by Anderson et al.,4 using a panel of monoclonal antibodies, failed to detect HLA-A, -B, -C, -DR or 132microglobulin on postmeiotic germ cells of testes or on sperm cells from the epididymides and ejaculates of men. Also, the contention Menge and Beer Editor's corner
693
that common antigens exist between sperm and lymphocytes is questioned in light of results of Beer and co-workers,5 in which the induction or anamnestic response of antisperm antibodies did not occur in women given injections of their husbands' lymphocytes. While sperm and leukocytes may share antigens, most, if not all, are probably species-specific. The lack of HLA antigens on sperm cells may account for the low incidence of cell-mediated autoimmune orchitis in man and the low association of infertility with measures of cell-mediated immunity. Thus, while sperm may not express HLA, the ejaculate usually contains other nucleated cells possessing HLA antigens (Le., leukocytes, epithelial cells) which under some conditions may sensitize the female partner against incompatible HLA antigens. Likewise, microbial and viral infections of the male reproductive tract may trigger leukocyte release of secretions capable of stimulating or potentiating immune responses in the male or female reproductive tract. Interferon-), is known to induce Ia expression in nonexpressing or poorly expressing cells, which in turn allows these cells to participate in antigen (sperm?, HLA?) processing and immune cell cooperation, initiating or promoting an immune response. A question still to be an_swered and relevant to the following section is whether or not the ejaculate normally sensitizes the female against antigens that would be expressed by a developing conceptus. Progress in our understanding of the critical features of the placental trophoblast for immune protection in the mother has burgeoned during the past 5 years.6 It can be stated with certainty that these critical features of the trophoblast are (1) resisting destruction by cytotoxic lymphocytes and antibodies; (2) forming a physical barrier to immune effector cells but not antibody, prohibiting them from reaching the fetus; (3) signaling the migration of suppressor or other functionally hyporesponsive lymphocytes to the uterine decidual and uterine lymphatics; (4) promoting the production of maternal serum mixed lymphocyte culture (MLC) blocking antibody with paternal specificity; (5) establishing receptors on its membrane which bind to agents in maternal plasma (Le., transferrin, epithelial growth factor, which have both transport and immunodirective function); (6) producing protein and steroid hormones in high local concentrations that have immunoregulatory .functions as well as regulating gene expression of cells at the maternal-fetal tissue 694
Menge ~d Beer Editor's corner
l
interface; and (7) sustaining the production of blocking antibodies that bind on a paternal-antigen-specific basis to its membrane. The question currently facing clinicians is whether HLA antigen screening and other immunologic screening6 identifies couples whose infertility, pregnancy wastage, or poor pregnancy performance is due to the failure of the trophoblast to perform in a timely manner these critical functions for immune protection in the mother, or is due to immunodeviation of their responses along cytotoxic lines that interfere with sperm function or viability or to responses that are cytotoxic to the preimplantation embryo. Unlike what has been reported in inbred strains of mice, mating in humans appears to be a random event, in that HLA antigen profiles between spouses do not vary from the expected. Also, the expected HLA antigen frequency between computer-mated individuals does not differ in any respect from the observed frequency in couples studied in Switzerland. 7 Many couples with recurrent abortions of unknown etiology, however, share significantly more HLA-B, -DR, and -MT locus antigens than control couples. 6 In addition, the following observations in aborting couples have been made: (1) HLA antigen frequency in the aborting group is comparable to that of fertile control subjects or of American Caucasians. (2) Aborting women do not show any differences in distribution of ABO blood types from those of fertile couples or those of couples tested for paternity determination. (3) The incidence of antisperm antibodies is not significantly elevated in this group. (4) Immunotherapy of aborting women with paternal leukocytes will sustain a subsequent pregnancy to term in those developing blocking factors in MLC, whereas in those women lacking the blocking factors abortions recur. (5) In over 300 couples evaluated, no woman positive for agglutinating and immobilizing sperm antibodies and also a recurrent aborter of unknown etiology has delivered a live-born infant. Support for the influence of HLA on fertility is provided by a prospective study in Hutterites by Ober et al. 8 that showed a marked decrease in fertility in couples sharing HLA-DR antigens. In a related study, they found an increased sex ratio among HLA-DR-compatible pregnancies in the same population. They postulate that the mechanism is that the H-Y antigen of male fetuses may compensate compatible pregnancies by providing
Fertility and Sterility
a sufficient antigenic stimulus to elicit a normal maternal immunologic response. 9 Immunologic concerns regarding immunotherapy of women with paternal leukocytes have arisen. Three of 2& women with three or more recurrent abortions who shared HLA antigens with their spouses and were found to lack some ofthose critical features of the trophoblast for immune protection in the mother were immunized with paternal leukocytes and became pregnant. All three experienced severe intrauterine growth retardation, evident by 22 weeks of pregnancy. In addition, parental HLA compatibility or compatibility at a locus near to HLA-A region in these couples may predispose them to produce children with anencephaly and other neural tube defects.!O In the same vein, there are reports that antigens of the HLA system may be involved in determining which genetically abnormal human infants are aborted and which are gestated to term. 11 In summary, we agree with Persitz and coworkers! that HLA antigen screening in individuals with primary infertility has not proven helpful; however, immunologic screening, including HLA typing of couples with recurrent abortions or anomalies of pregnancy, is beneficial and should be part of the workup in a case of infertility. Immunologic analyses evaluating maternal systemic responses as well as uterine decidual lymphoid cell responses to paternal alloantigens not routine in some laboratories can definitely identifY women who are abortion-prone after a full medical workup and in addition can identify those in whom immunotherapy may be dangerous, in that it may pass a problem on to the fetus (intrauterine growth retardation, neonatal acquired immune deficiency syndrome secondary to graft-versus-host disease, or placing the couple at risk of bearing a genetically abnormal child). Finally, immunologic screening has progressed to an art wherein aborting couples with no cause for their abortions can know whether altered immunologic responses underly their problem. HLA testing, in the minds of most experts, will identifY most, but not all, couples with reproductive failure, i.e., recurrent abortions. Prospective
Vol. 43, No.5, May 1985
studies indicate that HLA antigen sharing may identify couples who share other chromosomal material closely linked to HLA: a growth and reproduction locus similar to the Tit locus in the mouse, where mates homozygous for this locus experience reproductive inefficiency, fetuses with multiple anomalies, and primary infertility.!O In addition, couples sharing antigens at this locus may fail to initiate the protective immune responses or deviate them along lines cytotoxic or damaging to the fetoplacental unit. REFERENCES 1. Persitz E, Oksenberg JR, Margalioth EJ, Hacohen S, Schenker J, Brautbar C: Histoincompatibility in couples with unexplained infertility. Fertil Steril 43:733, 1985 2. Nordlander C, Fuchs T, Hammarstrom L, Smith CIE: Human leukocyte antigens group A in couples with unexplained infertility. Fertil Steril 40:60, 1983 3. Genco PV, Mathur S, Williamson HO, Rust PF, Glassman AB, Fudenberg HH: Antibodies to A19 and Bw35 com~ plexes of human leukocyte antigens are present in infertile subjects with sperm antibodies. Fertil Steril 42:554, 1984 4. Anderson DJ, Narayan P, DeWolf WC: Major histocompatibility antigens are not detectable on postmeiotic human testicular germ cells. J ImmunoI133:1962, 1984 5. Beer AE, Quebbeman JF, Semprini AE: Immunopathological factors contributing to recurrent spontaneous abortions in humans. In Spontaneous Abortions, Edited by ESE Hafez, DK Edmonds. London, Blackwell Scientific Publishers, 1985. In press 6. Beer AE, Semprini AE, Xiaoyu Z, Quebbeman JF: Pregnancy outcome in human couples with recurrent spontaneous abortions. Exp Clin Immunogenet. In press, 1985 7. Bischof P, Jeannet M, Bourrit B, Vuagnat P, Herrman WL, Sizonenko PC: Mating is random. Am J Reprod Immunol. In press, 1985 8. Ober CL, Hauck WW, Kostyu DD, O'Brien E, Elias S, Simpson JL, Martin AO: Adverse effects ofHLA-DR sharing on fertility: a cohort study in a human isolate. Fertil Steril. Submitted for publication 9. Ober CL, Simpson JL, Radvany R: Increased sex ratios among HLA-DR compatible pregnancies. Lancet. In press, 1985 10. Schacter B, Weitkamp LR, Johnson WE: Parental HLA compatibility, fetal wastage and neural tube defects: evidence for a TIt like locus in humans. Am J Hum Genet 36:1082,1984 11. Mottironi VD, Hook EB, Willey AM, Porter IH, Swift RV, Hatcher NH: Decreased HLA heterogenicity in parents of children with Down Syndrome. Am J Hum Genet 35: 1289, 1983
Menge and Beer Editor's corner
695