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Histocompatibility antigens associated with motor neurone disease
Journal of the Neurological Sciences, 1977, 32: 213-217 © Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
213
H I S T O C O M P A T I B I L I T Y A N T I G E N S ASSOCIATED W I T H M O T O R N E U R O N E DISEASE
PETER O. BEHAN, HEATHER M. DICK and WILLIAM F. DURWARD Department of Neurology, Institute of Neurological Sciences, Glasgow (Great Britain)
(Received 30 September, 1976)
SUMMARY The distribution of histocompatibility antigens was studied in 44 patients with motor neurone disease (MND). An unusually high incidence of H L A antigens A2 and A28 was found, compared to a control population.
INTRODUCTION Motor neurone disease (MND) is characterized clinically by rapidly progressive weakness and muscular wasting without mental deterioration or sensory loss. Historically, cases have been divided into three different groups, namely: progressive muscular atrophy (Aran-Duchenne), progressive bulbar palsy (Duchenne) and amyotrophic lateral sclerosis (Charcot). This division is now accepted as artificial and all three groups are considered to form a single disease spectrum. The central pathological feature of this disease is degeneration of the motor neurone cells. The disease usually appears after 50 years of age but may occur at any time. In Europe and North America the death rate has been calculated as 1 per 100,000 of the population accounting for 1 per 1000 of all adult deaths (Bobowick and Brody 1973). M N D is commoner than myasthenia gravis but not as common as multiple sclerosis. Death occurs on average within 3 years. Amyotrophic lateral sclerosis (ALS) is more frequent in males (1.6:1) but bulbar palsy is probably commoner in females. The prevalence rate for M N D in general is 4 per 100,000 but in Guam it is 200 per 100,000 due to its high incidence in the Chamorro people, in which it accounts for 1 0 ~ of all deaths in adults (Bobowick and Brody 1973). A similarly high incidence has been found in the Kii peninsula of Japan (Kusui 1962; Araki, Iwatashi and KuThis work was supported by the Muscular Dystrophy Group of Great Britain. A preliminary report of these investigations was presented at the First International Symposium on HLA and Disease, Paris, 23-25 June, 1976.
214 roiwa 1967). Most cases elsewhere occur sporadically b u t 32 secondary cases were f o u n d a m o n g 1008 relatives in ten studies o f the familial occurrence of M N D (Pratt 1967), a n d families have been described in which the disease has been inherited as an a u t o s o m a l d o m i n a n t trait ( K u r l a n d a n d M u l d e r 1955; Roe 1964). Viruses a n d i m m u n o l o g i c a l factors m a y be involved in the pathogenesis o1' M N D ( M c K h a n n a n d J o h n s o n 1973) a n d for this reason we u n d e r t o o k a study o f a large g r o u p o f patients to determine their H L A status. PATIENTS Thirty-three male a n d 11 female patients with a definite diagnosis o f m o t o r n e u r o n e disease were studied. I n 35 patients the disease was manifest initially as a m y o t r o p h i c lateral sclerosis whilst in 9 it presented as progressive b u l b a r palsy which later became generalised. The patients' ages ranged f r o m 38 to 72 years with a m e a n age of 61. The average d u r a t i o n o f the disease was 4 years. The clinical diagnosis in all cases was confirmed by electromyography. In 7 patients transfer factor therapy was given over a 3 - m o n t h period a n d consisted in each case o f a total o f 3 m o n t h l y injections o f transfer factor prepared from 500 ml o f venous blood taken f r o m a y o u n g healthy donor, negative for syphilis a n d Australia antigen. The m e t h o d of transfer factor p r e p a r a t i o n was as described by Laurence a n d A l - A s k a r i (1971). A n additional 2 patients had a 6 - m o n t h trial of imm u n o s u p p r e s s i v e therapy, receiving azathioprine 120 mg daily.
TABLE l HLA A AND B SERIES ANTIGENS A Series
B Series Patients (N =44) Controls (N ~ 342)
Patients (N=44) Controls (N = 342)
No.
%
No.
%
No.
%
No.
%
AI 2 3 9 10 W25 ~ W26 t 11 28 29 W30
19 25 8 5 3 I 2 1 7 0 2
43.2 56.8 18.2 11.4 6.8
138 163 78 60 21
40.3 47.6 22.8 17.5 6.1
2.3 15.9 0 4.5
26 31 16 9
7.6 9.0 4.7 2.6
W3I W32 W33 "WI9" Blank
I 0 I 1 15
2.3 0 2.3 2.3 34
12 14 ND
3.5 4.1 --
ND
--
l 13 12 II 1 8 3 2 7 3 5 0 l 4 l 6 l0
2.3 29.5 27.2 25.0 2.3 18.1 6.8 4.5 15.9 6.8 11.4 0 2.3 9.1 2.3 13.6 22.7
21 93 105 114 15 34 19 27 29 10 26 7 13 29 ND 30 ND
6.1 27.1 30.7 33.3 4.3 9.9 5.5 7.9 8.5 2.9 7.6 2.0 3.8 8.5 --8.8 --
B5 7 8 12 13 14 18 27 WI5 WI6 W17 W21 W22 W35 W37 W40 Blank
215 TISSUE TYPING Tissue typing was carried out using a microcytoxicity technique with peripheral blood lymphocytes isolated by Ficoll/Hypaque centrifugation. The HLA antigens sought included, from the A series: A1, 2, 3, 9, 10, 11, 28, 29, W25, W26, W30, W31, W32 and W33; from the B series: B5, 7, 8, 12, 13, 14, 18, 27, W15, W16, W17, W21, W22, W35, W37 and W40. At least 2 sera were used to determine each specificity and for most antigens, 3 or more sera. The control population consisted of 342 random (unrelated) healthy individuals, drawn from the same geographical region of the West of Scotland as the patients. RESULTS The HLA antigen frequencies are presented in Table 1. C locus antigens were not tested for in this study. There was a disturbance in the expected frequency of the HLA antigens: A2 -I- A28 = 32 i.e. 72.7 A2 Z2 = 1.3 (not significant) A28 Z2 ---- 2.0 (not significant) A2q-28Z2=4.1 P<0.05 This P is not significant when multiplied by the number of antigens tested for. Transfer factor and immunosuppressive therapy was without apparent clinical effect. DISCUSSION All patients in this study had definite motor neurone disease with the typical gross wasting, fasciculations, hyperreflexia, absence of sensory abnormalities and electromyographic findings. One patient had a positive family history, his father dying of a similar condition. Most cases, apart from those in Guam, the Kii peninsula of Japan and New Guinea, are considered to be sporadic but about 5-10 ~o of ALS cases outside these areas are familial (Kurland and Mulder 1955; Roe 1964), a sib being more often affected than a parent (Pratt 1962). The occurrence of MND in families may be because there is exposure to a particular environmental agent since the familial incidence found is similar to that in multiple sclerosis and in the latter condition there is clear evidence that both histocompatibility determinants and an environmental infective agent play a role (Bertrams and Kuwert 1972; Carp, Licursi, Merz and Merz 1972). Significant associations have been reported between certain HLA antigens and various disease states, particularly those with immunological features. Antigens of the HLA B series have been primarily implicated, e.g. B8 in myasthenia gravis (Behan, Simpson and Dick 1973; Dick, Behan, Simpson and Durward 1974). In considering HLA antigen association with a particular disease, it has been postulated that the crucial factor is the inheritance of genetic information coded for by a series of immune
216 response (lr) genes which are located in or very close to the major histocompatibility system (MHS). This may explain why the association between HLA antigens and disease states is not an absolute one since there are always some patients with the disease who do not have the specific HLA antigen and vice versa. Even in ankylosing spondylitis where the association between B27 and the disease is extremely close, approximately 10 j°.o of patients with frank spinal disease do not have the antigen B27. Our findings are of a slightly increased number of patients with HLA antigen A2 together with an unuasul increase in the frequency of antigen A28. These antigens are known to show very strong serological cross-reactivity and are generally considered to have a strong resemblance to each other. When we pool the results for A2 and A28 we find an increase in the number of patients who carry one or other of these antigens, an increase which is significant. There have been few reports of associations between antigens of the HLA A series and disease. An increase in HLA A2 has been noted in myasthenic patients with thymoma and antibodies to skeletal muscle (Feltkamp, Van den Berg-Loonen, Nijenhuis, Engelfriet, Van Loghem and Oosterhuis (1974), a trend which was also noticeable in our series of patients with this disorder (Dick and Behan, unpublished). An increased frequency of H LA A I has been found in a group of 36 children with immune deficiency diseases (Hors, Griscelli, Schmid and Dausset 1974). These observations might suggest that there is a gene close to the HLA-A locus, involved in the control of differentiation and indirectly contributing to the immune response. One explanation for the association between HLA antigens and disease is that these antigens on the surface of cells may facilitate cell penetration by specific viruses. Such a possibility is suggested by the relationship between the H2 locus in the mouse (considered analogous to HLA in man)and susceptibility to the development of Gross virus leukaemia (Lilly, Boyse and Old 1964). Attempts to isolate a virus from patients with MND, using chimpanzees have not been successful (Gibbs and Gajdusek 1969) and a relationship to viruses in this disease is difficult to assess although there is some evidence to suggest such an association. For instance, in a report of 275 consecutive cases, 50//o gave histories of poliomyelitis and had evidence of residual, focal muscle wasting. The poliomyelitic illness had occurred several years previously and there had been no further deterioration until onset of motor neurone disease (Norris 1975). There are several other reports in the literature of previous polio in M N D and the incidence has been stated to be between 2 j~, and 8 .~ for all cases (Zilkha 1962; Campbell, Williams and Pearce 1964; Poskanzer, Cantor and Kaplan 1969; Norris 1975). It is of interest also that the one murine animal model for this disease is associated with C-type particle RNA virus (McKhann and Johnson 1973). Deposition of IgG and C3 in a granular pattern on the glomerular basement membrane and in the mesangium, suggesting antigen-antibody localization, has also been demonstrated by immunofluorescence in renal biopsies from patients with M N D (Norris 1975). There have been no claims for the efficacy of either transfer factor or immunosuppressive therapy since their use was suggested in this disease (McKhann and Johnson 1973). The small number of patients in our study does not allow any conclusions to be drawn. Our finding of an HLA-linked association in M N D suggests an immunopathological aetiology.
217 REFERENCES Araki, S., Y. Iwatashi, and Y. Kuroiwa (1967) Epidemiological study of amyotrophic lateral sclerosis and allied disorders in the Kii Peninsula (Japan), J. neurol. Sci., 4: 279-287. Behan, P. O., J. A. Simpson and H. M. Dick (1973) Immune response genes in myasthenia gravis, Lancet, 2: 1033, 1220. Bertrams, J. and E. Kuwert (1972) HL-A antigen frequencies in multiple sclerosis, Europ. NeuroL, 7: 74-78. Bobowick, A. R. and J. A. Brody (1973) Epidemiology of motor-neuron diseases, New Engl. J. Med., 288 : 1047-1055. Campbell, A. M. G., E. R. Williams and J. Pearce (1964) Late motor neuron degeneration following poliomyelitis, Neurology (Minneap.), 19 : 1101-1106. Carp, R. I., P. C. Licursi, P. A. Merz and G. S. Merz (1972) Decreased percentage of polymorphonuclear neutrophils in mouse peripheral blood after inoculation with material from multiple sclerosis patients, J. exp. Med., 136: 618-629. Dick, H. M., P. O. Behan, J. A. Simpson and W. F. Durward (1974) The inheritance of HL-A antigens in myasthenia gravis, J. Immunogenet., 1 : 401-412. Feltkamp, T. E. W., P. M. Van den Berg-Loonen, L. E. Nijenhuis, C. P. Engelfriet, J. J. Van Loghem and H. J. G. H. Oosterhuis (1974) Myasthenia gravis, autoantibodies and HL-A antigens, Brit. reed. J., 1 : 131-133. Gibbs, C. J. and D. C. Gajdusek (1969) Kuru - - A prototype subacute infectious disease of the nervous system as a model for the study of amyotrophic lateral sclerosis. In: F. H. Norris, Jr. and L. T. Kurland (Eds.), Motor Neurone Diseases - - Research on Amyotrophic Lateral Sclerosis and Related Disorders, Grune and Stratton, New York, N.Y., pp. 269-279. Hors, J., C. Griscelli, M. Schmid and J. Dausset (1974) HL-A antigens and immune deficiency states, Brit. reed. J., 2: 45. Kurland, L. T. and D. W. Mulder (1955) Epidemiologic investigations of amyotrophic lateral sclerosis - - Familial aggregations indicative of dominant inheritance, Part I and Part II, Neurology (Minneap.), 5:182-196 and 249-268. Kusui, K. (1962) Epidemiologic study on amyotrophic lateral sclerosis (ALS) and other neighbouring motor neuron diseases in the Kii peninsula, Psychiat. Neurol. Jap., 64: 85-99. Laurence, H. S. and S. AI-Askari (1971) The preparation and purification of transfer factor. In: B. R. Bloom and P. Glade (Eds.), In Vitro Methods of Cell-Mediated Immunity, Academic Press, New York, N.Y., 19. 531. Lilly, F., E. A. Boyse and L. J. Old (1964) Genetic basis of susceptibility to viral leukemogenesis, Lancet, 2: 1207. McKhann, G. M. and R. T. Johnson (1973) Amyotrophic lateral sclerosis - - Summary of a conference, Science, 180: 221-222. Norris, F. H. (1975) Recent advances in motor neurone diseases. In: W. G. Bradley, D. GardnerMedwin and J. N. Walton (Eds.), Recent Advances in Myology (Proceedings of the 3rd International Congress on Muscle Diseases, Newcastle upon Tyne, September, 1974) (International Congress Series, No. 360), Excerpta Medica, Amsterdam, 1975, pp. 522-536. Poskanzer, D. C., H. M. Cantor and G. S. Kaplan (1969) The frequency of preceding poliomyelitis in amyotrophic lateral sclerosis. In: F. H. Norris, Jr. and L. T. Kurland (Eds.), Motor Neurone Diseases - - Research on Amyotrophic Lateral Sclerosis and Related Disorders, Grune and Stratton, New York, N.Y., pp. 286-290. Pratt, R. T. C. (1962) Discussion on motor neurone disease, Proc. roy. Soc. Med., 55: 40-41. Pratt, R. T. C. (1967) Motor neurone disease. In: The Genetics of Neurological Disorders, Oxford University Press, London, p. 53. Roe, P. F. (1964) Familial motor neurone disease, J. Neurol. Neurosurg. Psychiat., 27" 140-143. Zilkha, K. J. (1962) Discussion on motor neuron disease, Proc. roy. Soc. Med., 55 : 48-49.
213
H I S T O C O M P A T I B I L I T Y A N T I G E N S ASSOCIATED W I T H M O T O R N E U R O N E DISEASE
PETER O. BEHAN, HEATHER M. DICK and WILLIAM F. DURWARD Department of Neurology, Institute of Neurological Sciences, Glasgow (Great Britain)
(Received 30 September, 1976)
SUMMARY The distribution of histocompatibility antigens was studied in 44 patients with motor neurone disease (MND). An unusually high incidence of H L A antigens A2 and A28 was found, compared to a control population.
INTRODUCTION Motor neurone disease (MND) is characterized clinically by rapidly progressive weakness and muscular wasting without mental deterioration or sensory loss. Historically, cases have been divided into three different groups, namely: progressive muscular atrophy (Aran-Duchenne), progressive bulbar palsy (Duchenne) and amyotrophic lateral sclerosis (Charcot). This division is now accepted as artificial and all three groups are considered to form a single disease spectrum. The central pathological feature of this disease is degeneration of the motor neurone cells. The disease usually appears after 50 years of age but may occur at any time. In Europe and North America the death rate has been calculated as 1 per 100,000 of the population accounting for 1 per 1000 of all adult deaths (Bobowick and Brody 1973). M N D is commoner than myasthenia gravis but not as common as multiple sclerosis. Death occurs on average within 3 years. Amyotrophic lateral sclerosis (ALS) is more frequent in males (1.6:1) but bulbar palsy is probably commoner in females. The prevalence rate for M N D in general is 4 per 100,000 but in Guam it is 200 per 100,000 due to its high incidence in the Chamorro people, in which it accounts for 1 0 ~ of all deaths in adults (Bobowick and Brody 1973). A similarly high incidence has been found in the Kii peninsula of Japan (Kusui 1962; Araki, Iwatashi and KuThis work was supported by the Muscular Dystrophy Group of Great Britain. A preliminary report of these investigations was presented at the First International Symposium on HLA and Disease, Paris, 23-25 June, 1976.
214 roiwa 1967). Most cases elsewhere occur sporadically b u t 32 secondary cases were f o u n d a m o n g 1008 relatives in ten studies o f the familial occurrence of M N D (Pratt 1967), a n d families have been described in which the disease has been inherited as an a u t o s o m a l d o m i n a n t trait ( K u r l a n d a n d M u l d e r 1955; Roe 1964). Viruses a n d i m m u n o l o g i c a l factors m a y be involved in the pathogenesis o1' M N D ( M c K h a n n a n d J o h n s o n 1973) a n d for this reason we u n d e r t o o k a study o f a large g r o u p o f patients to determine their H L A status. PATIENTS Thirty-three male a n d 11 female patients with a definite diagnosis o f m o t o r n e u r o n e disease were studied. I n 35 patients the disease was manifest initially as a m y o t r o p h i c lateral sclerosis whilst in 9 it presented as progressive b u l b a r palsy which later became generalised. The patients' ages ranged f r o m 38 to 72 years with a m e a n age of 61. The average d u r a t i o n o f the disease was 4 years. The clinical diagnosis in all cases was confirmed by electromyography. In 7 patients transfer factor therapy was given over a 3 - m o n t h period a n d consisted in each case o f a total o f 3 m o n t h l y injections o f transfer factor prepared from 500 ml o f venous blood taken f r o m a y o u n g healthy donor, negative for syphilis a n d Australia antigen. The m e t h o d of transfer factor p r e p a r a t i o n was as described by Laurence a n d A l - A s k a r i (1971). A n additional 2 patients had a 6 - m o n t h trial of imm u n o s u p p r e s s i v e therapy, receiving azathioprine 120 mg daily.
TABLE l HLA A AND B SERIES ANTIGENS A Series
B Series Patients (N =44) Controls (N ~ 342)
Patients (N=44) Controls (N = 342)
No.
%
No.
%
No.
%
No.
%
AI 2 3 9 10 W25 ~ W26 t 11 28 29 W30
19 25 8 5 3 I 2 1 7 0 2
43.2 56.8 18.2 11.4 6.8
138 163 78 60 21
40.3 47.6 22.8 17.5 6.1
2.3 15.9 0 4.5
26 31 16 9
7.6 9.0 4.7 2.6
W3I W32 W33 "WI9" Blank
I 0 I 1 15
2.3 0 2.3 2.3 34
12 14 ND
3.5 4.1 --
ND
--
l 13 12 II 1 8 3 2 7 3 5 0 l 4 l 6 l0
2.3 29.5 27.2 25.0 2.3 18.1 6.8 4.5 15.9 6.8 11.4 0 2.3 9.1 2.3 13.6 22.7
21 93 105 114 15 34 19 27 29 10 26 7 13 29 ND 30 ND
6.1 27.1 30.7 33.3 4.3 9.9 5.5 7.9 8.5 2.9 7.6 2.0 3.8 8.5 --8.8 --
B5 7 8 12 13 14 18 27 WI5 WI6 W17 W21 W22 W35 W37 W40 Blank
215 TISSUE TYPING Tissue typing was carried out using a microcytoxicity technique with peripheral blood lymphocytes isolated by Ficoll/Hypaque centrifugation. The HLA antigens sought included, from the A series: A1, 2, 3, 9, 10, 11, 28, 29, W25, W26, W30, W31, W32 and W33; from the B series: B5, 7, 8, 12, 13, 14, 18, 27, W15, W16, W17, W21, W22, W35, W37 and W40. At least 2 sera were used to determine each specificity and for most antigens, 3 or more sera. The control population consisted of 342 random (unrelated) healthy individuals, drawn from the same geographical region of the West of Scotland as the patients. RESULTS The HLA antigen frequencies are presented in Table 1. C locus antigens were not tested for in this study. There was a disturbance in the expected frequency of the HLA antigens: A2 -I- A28 = 32 i.e. 72.7 A2 Z2 = 1.3 (not significant) A28 Z2 ---- 2.0 (not significant) A2q-28Z2=4.1 P<0.05 This P is not significant when multiplied by the number of antigens tested for. Transfer factor and immunosuppressive therapy was without apparent clinical effect. DISCUSSION All patients in this study had definite motor neurone disease with the typical gross wasting, fasciculations, hyperreflexia, absence of sensory abnormalities and electromyographic findings. One patient had a positive family history, his father dying of a similar condition. Most cases, apart from those in Guam, the Kii peninsula of Japan and New Guinea, are considered to be sporadic but about 5-10 ~o of ALS cases outside these areas are familial (Kurland and Mulder 1955; Roe 1964), a sib being more often affected than a parent (Pratt 1962). The occurrence of MND in families may be because there is exposure to a particular environmental agent since the familial incidence found is similar to that in multiple sclerosis and in the latter condition there is clear evidence that both histocompatibility determinants and an environmental infective agent play a role (Bertrams and Kuwert 1972; Carp, Licursi, Merz and Merz 1972). Significant associations have been reported between certain HLA antigens and various disease states, particularly those with immunological features. Antigens of the HLA B series have been primarily implicated, e.g. B8 in myasthenia gravis (Behan, Simpson and Dick 1973; Dick, Behan, Simpson and Durward 1974). In considering HLA antigen association with a particular disease, it has been postulated that the crucial factor is the inheritance of genetic information coded for by a series of immune
216 response (lr) genes which are located in or very close to the major histocompatibility system (MHS). This may explain why the association between HLA antigens and disease states is not an absolute one since there are always some patients with the disease who do not have the specific HLA antigen and vice versa. Even in ankylosing spondylitis where the association between B27 and the disease is extremely close, approximately 10 j°.o of patients with frank spinal disease do not have the antigen B27. Our findings are of a slightly increased number of patients with HLA antigen A2 together with an unuasul increase in the frequency of antigen A28. These antigens are known to show very strong serological cross-reactivity and are generally considered to have a strong resemblance to each other. When we pool the results for A2 and A28 we find an increase in the number of patients who carry one or other of these antigens, an increase which is significant. There have been few reports of associations between antigens of the HLA A series and disease. An increase in HLA A2 has been noted in myasthenic patients with thymoma and antibodies to skeletal muscle (Feltkamp, Van den Berg-Loonen, Nijenhuis, Engelfriet, Van Loghem and Oosterhuis (1974), a trend which was also noticeable in our series of patients with this disorder (Dick and Behan, unpublished). An increased frequency of H LA A I has been found in a group of 36 children with immune deficiency diseases (Hors, Griscelli, Schmid and Dausset 1974). These observations might suggest that there is a gene close to the HLA-A locus, involved in the control of differentiation and indirectly contributing to the immune response. One explanation for the association between HLA antigens and disease is that these antigens on the surface of cells may facilitate cell penetration by specific viruses. Such a possibility is suggested by the relationship between the H2 locus in the mouse (considered analogous to HLA in man)and susceptibility to the development of Gross virus leukaemia (Lilly, Boyse and Old 1964). Attempts to isolate a virus from patients with MND, using chimpanzees have not been successful (Gibbs and Gajdusek 1969) and a relationship to viruses in this disease is difficult to assess although there is some evidence to suggest such an association. For instance, in a report of 275 consecutive cases, 50//o gave histories of poliomyelitis and had evidence of residual, focal muscle wasting. The poliomyelitic illness had occurred several years previously and there had been no further deterioration until onset of motor neurone disease (Norris 1975). There are several other reports in the literature of previous polio in M N D and the incidence has been stated to be between 2 j~, and 8 .~ for all cases (Zilkha 1962; Campbell, Williams and Pearce 1964; Poskanzer, Cantor and Kaplan 1969; Norris 1975). It is of interest also that the one murine animal model for this disease is associated with C-type particle RNA virus (McKhann and Johnson 1973). Deposition of IgG and C3 in a granular pattern on the glomerular basement membrane and in the mesangium, suggesting antigen-antibody localization, has also been demonstrated by immunofluorescence in renal biopsies from patients with M N D (Norris 1975). There have been no claims for the efficacy of either transfer factor or immunosuppressive therapy since their use was suggested in this disease (McKhann and Johnson 1973). The small number of patients in our study does not allow any conclusions to be drawn. Our finding of an HLA-linked association in M N D suggests an immunopathological aetiology.
217 REFERENCES Araki, S., Y. Iwatashi, and Y. Kuroiwa (1967) Epidemiological study of amyotrophic lateral sclerosis and allied disorders in the Kii Peninsula (Japan), J. neurol. Sci., 4: 279-287. Behan, P. O., J. A. Simpson and H. M. Dick (1973) Immune response genes in myasthenia gravis, Lancet, 2: 1033, 1220. Bertrams, J. and E. Kuwert (1972) HL-A antigen frequencies in multiple sclerosis, Europ. NeuroL, 7: 74-78. Bobowick, A. R. and J. A. Brody (1973) Epidemiology of motor-neuron diseases, New Engl. J. Med., 288 : 1047-1055. Campbell, A. M. G., E. R. Williams and J. Pearce (1964) Late motor neuron degeneration following poliomyelitis, Neurology (Minneap.), 19 : 1101-1106. Carp, R. I., P. C. Licursi, P. A. Merz and G. S. Merz (1972) Decreased percentage of polymorphonuclear neutrophils in mouse peripheral blood after inoculation with material from multiple sclerosis patients, J. exp. Med., 136: 618-629. Dick, H. M., P. O. Behan, J. A. Simpson and W. F. Durward (1974) The inheritance of HL-A antigens in myasthenia gravis, J. Immunogenet., 1 : 401-412. Feltkamp, T. E. W., P. M. Van den Berg-Loonen, L. E. Nijenhuis, C. P. Engelfriet, J. J. Van Loghem and H. J. G. H. Oosterhuis (1974) Myasthenia gravis, autoantibodies and HL-A antigens, Brit. reed. J., 1 : 131-133. Gibbs, C. J. and D. C. Gajdusek (1969) Kuru - - A prototype subacute infectious disease of the nervous system as a model for the study of amyotrophic lateral sclerosis. In: F. H. Norris, Jr. and L. T. Kurland (Eds.), Motor Neurone Diseases - - Research on Amyotrophic Lateral Sclerosis and Related Disorders, Grune and Stratton, New York, N.Y., pp. 269-279. Hors, J., C. Griscelli, M. Schmid and J. Dausset (1974) HL-A antigens and immune deficiency states, Brit. reed. J., 2: 45. Kurland, L. T. and D. W. Mulder (1955) Epidemiologic investigations of amyotrophic lateral sclerosis - - Familial aggregations indicative of dominant inheritance, Part I and Part II, Neurology (Minneap.), 5:182-196 and 249-268. Kusui, K. (1962) Epidemiologic study on amyotrophic lateral sclerosis (ALS) and other neighbouring motor neuron diseases in the Kii peninsula, Psychiat. Neurol. Jap., 64: 85-99. Laurence, H. S. and S. AI-Askari (1971) The preparation and purification of transfer factor. In: B. R. Bloom and P. Glade (Eds.), In Vitro Methods of Cell-Mediated Immunity, Academic Press, New York, N.Y., 19. 531. Lilly, F., E. A. Boyse and L. J. Old (1964) Genetic basis of susceptibility to viral leukemogenesis, Lancet, 2: 1207. McKhann, G. M. and R. T. Johnson (1973) Amyotrophic lateral sclerosis - - Summary of a conference, Science, 180: 221-222. Norris, F. H. (1975) Recent advances in motor neurone diseases. In: W. G. Bradley, D. GardnerMedwin and J. N. Walton (Eds.), Recent Advances in Myology (Proceedings of the 3rd International Congress on Muscle Diseases, Newcastle upon Tyne, September, 1974) (International Congress Series, No. 360), Excerpta Medica, Amsterdam, 1975, pp. 522-536. Poskanzer, D. C., H. M. Cantor and G. S. Kaplan (1969) The frequency of preceding poliomyelitis in amyotrophic lateral sclerosis. In: F. H. Norris, Jr. and L. T. Kurland (Eds.), Motor Neurone Diseases - - Research on Amyotrophic Lateral Sclerosis and Related Disorders, Grune and Stratton, New York, N.Y., pp. 286-290. Pratt, R. T. C. (1962) Discussion on motor neurone disease, Proc. roy. Soc. Med., 55: 40-41. Pratt, R. T. C. (1967) Motor neurone disease. In: The Genetics of Neurological Disorders, Oxford University Press, London, p. 53. Roe, P. F. (1964) Familial motor neurone disease, J. Neurol. Neurosurg. Psychiat., 27" 140-143. Zilkha, K. J. (1962) Discussion on motor neuron disease, Proc. roy. Soc. Med., 55 : 48-49.