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Immunologic evaluation of patients with ischemic heart disease
195
A tkerosclerosis,
36 (1980)
0 Elsevier/North-Holland
IMMUNOLOGIC DISEASE
195-200 Scientific
Publishers,
EVALUATION
Genetic
Determination
MAGNUS
BJGRKHOLM,
OF PATIENTS WITH ISCHEMIC HEART
and Relation
ULF
Ltd.
DE FAIRE
to Disease
and G6RAN
Department of Medicine, Seraphimer Hospital, Stockholm Immunology, Huddinge Hospital, Huddinge (Sweden) (Received 8 October, 1979) (Revised, received 29 December, (Accepted 8 January, 1980)
GOLM
’
and ’ Department
of Clinical
1979)
Summary Delayed skin hypersensitivity and serum immunoglobulins were studied in relation to the severity of ischemic heart disease in 18 male monozygotic and 13 male dizygotic twin pairs, aged 55-78 years. The twin pairs were selected from the Swedish Twin Registry. Low IgG was seen in patients with myocardial infarction and definitive angina pectoris. No correlation between skin anergy and the severity of ischemic heart disease was found. These findings may support the possibility that immunological mechanisms play a part in the pathogenesis of ischemic heart disease. Significant F-ratios for IgA and differential white cell count support a genetic determination of these variables. Key words:
Immunodeficiency
-Zschemic
heart disease - Twins
Introduction The etiology and development of atherosclerosis remain to a large extent unknown despite intense scientific efforts to elucidate this crucial issue. During the last decades most studies have been focused on abnormalities in the lipid metabolism especially that of cholesterol. However, advanced atherosclerosis can also be found in patients with normal or subnormal serum cholesterol levels [ 11. Since the late sixties some interest has been devoted to the immunological Please address reprint requests to: Dr Magnus BjGrkholm. Department of Medicine. Danderyd’s HosS-18288 Danderyd, Sweden.
Pital.
196
aspects of atherosclerosis [ 21. As the immune system is in direct contact with most tissues of the body, changes in the immunoreactivity may be expected to contribute to tissue damage in many organs. Autoantibodies against vascular antigens and antimyocardial antibodies have been demonstrated in patients with different vascular diseases [3,4]. It has been postulated that immune complexes play a central part in the development of arterial lesions [2,5,6]. Recent animal experiments support the hypothesis that antibodies to dietary proteins accelerate the development of atherosclerosis. The vascular changes may be mediated by immune complexes [7,8]. Moreover, myocardial infarction associated with coronary lesions are commonly present in mice with lupus syndrome [ 91. Atherosclerosis normally affects middle aged and elderly people. With increasing age immunological defects in cell mediated immunity develop in the normal population [ 10-121. It has been postulated that the normal immunological ageing may promote the development of atherosclerosis [13, 141. In the present study monozygotic and dizygotic twins, concordant and discordant with regard to ischemic heart disease, have been tested immunologically to determine whether evidence for immune alterations associated with underlying ischemic heart disease could be adduced. Moreover, the genetic determination of certain immunological and routine blood tests are presented. Materials and Methods Patient population The twin sample which derives from the Swedish Twin Registry [15] constitutes a follow-up of twin pairs earlier examined in 1967-1968 [ 161. It now consists of 31 male twin pairs, 18 monozygotic (MZ) and 13 dizygotic (DZ) aged 55-78 years (mean 66 years). These pairs had been selected by means of the angina pectoris questionnaire method according to Rose [ 171. Pairs judged to be concordant or discordant with regard to the probable presence of IHD at the examination in 1967-1968 were invited to a re-examination performed at Serafimerlasarettet. Controls The age-matched control material for delayed skin hypersensitivity consisted of 40 healthy persons from the laboratory and hospital staff and some of their parents.
TABLE 1 CLASSIFICATION
OF ISCHEMIC HEART DISEASE
Group 1: Myocardial infarction Group 2: Angina pectoris and ST-segment depressions > 0.5 mm at eXerCiSe. Group 3: (a) Angina pectoris without ST-segment depression > 0.5 mm at exercise. (b)no angina pectoris symptoms but ST-segment depressions > 0.5 mm at eXerCiSe. Group 4: Suspected angina pectoris without the above ECG changes. Group 5: None of the findings in groups l-4.
197
Classification
of IHD
The presence of IHD was established by means of the clinical history and electrocardiographic recordings at rest and during physical excercise. Various clinical manifestations of IHD were grouped according to a five-graded scale (Table 1) described by Liljefors [ 161. Patients in groups 1 and 2 had definite signs of ischemic heart disease, whereas those in groups 3-5 lacked these diagnostic criteria. Direct classification of the degree of coronary atherosclerosis by means of coronary angiography could not be performed for ethical reasons. Zygosity
determination
The zygosity diagnoses were based exclusively on diagnoses already made in 1967-1968, i.e. similarity questions, and in case of uncertainty on serologic determination which comprised the blood group systems ABO, MN, P, K, KE, FY, Ik and Rh and the serum groups Gn, Gc and Hp [ 161. Immunological
studies
Special attention was focused on the history of frequent infections, malignant tumors, hypersensitivity and autoimmune diseases among the patients and their relatives.
Delayed
skin hypersensitivity
All patients received intradermal injections of 0.1 ml mumps skin test antigen (Eli Lilly & Co, Indianapolis, U.S.A.) and Candida al&cans antigen (dermatophytin “O”, Hollister Stier Lab) on the volar surface of the right forearm. Purified protein derivate of tuberculin (2TU PPD, State Serum Institute, Copenhagen, Denmark) was injected on the volar surface of the left forearm. Skin reactions were evaluated after 48 h. A mean diameter of induration of 6 mm or more was considered positive. Immunoglobulins were quantitated by the rocket technique according to Laurel1 [ 181. Other tests
Hemoglobin concentration, WBC (including differential acute phase reactants were also determined.
counts), ESR and
Statistics
Intrapair variances for the different immunological and hematological measurements were calculated according to Osborne and deGeorge [19,for both MZ and DZ series. Ratios (F-ratios) between the intrapair variance for DZ and MZ series were calculated as well and tested for statistical significance by means of F-distribution. In order to test significance levels of differences between means, t-tests were used. As a measure of association for each pair of variables, Pearsons’ product moment correlation (r) has been chosen. Results Concordance and discordance for IHD The distribution of twin pairs with regard to severity of IHD is evident from
198
IHD Group 1
2
MZ
DZ
Partner
Partner
3
4
5
1
2
3
4
5
Fig. 1. Distribution of pairs according to IHD group. Numbers within circles denote pairs concordant for IHD group.
Fig. 1. Myocardial infarction (IHD group 1) was recorded in 9 of 18 MZ pairs and in 9 of 13 DZ pairs. In 3 of the MZ pairs both twins had had myocardial infarctions as compared to one of the DZ pairs. Concordance for the same IHD group was recorded in 6 MZ pairs and in only one DZ pair. Thus, 12 MZ pairs and 12 DZ pairs were discordant for the same IHD group. We could demonstrate no differences in the family histories of patients with IHD (groups 1 and 2) and without IHD (groups 3,4 and 5). Moreover, no common denominator with regard to IHD was found in the patients’ histories. The mean age of IHD patients was 67 years as compared to 65 years in patients without IHD (Table 2). The ability to respond to PPD, mumps and Candida antigens did not differ between the groups. The IgM and IgA concentrations, the Hb values and WBC counts were also comparable, but IgG was lower in groups 1 and 2 (Table 2).
TABLE 2 CLINICAL
VARIABLES
IN RELATION
TO IHD (mean f SD)
Variable
IHD l-2 (xl = 30)
Age (yr) Hb (gfl) WBC (X109/1) Total lymphocytes (X109/1) ESR (mm/l h) HaptogIobin (PP) aI-Antitrypsin (B/l) Albumin (g/l) IgG (g/1) IgM U/l) IgA (g/I) PPD Induration > 6 mm Mumps induration > 6 mm Candida induration > 6 mm
67 154 5.8 1.9 14 1.2 2.2 44 8.1 1.02 1.36 15 9 10
a NS = not significant.
P-value
IHD 3-5 (n = 32) * 5 * 17 * 2.2 * 1.0 * 14 f 0.6 * 0.5 + 3.6 + 2.0 + 0.64 + 0.78
65 153 5.3 1.7 12 1.2 2.2 45 10.1 1.00 1.51 15 10 9
* 7 * 12 * 1.7 * 0.8 * 12 + 0.6 * 0.4 * 4.3 * 1.9 + 0.40 * 0.74
NS a NS NS NS NS NS NS NS NS NS NS NS NS NS
199 TABLE 3 INTRAPAIR
VARIANCE
RATIOS
(F-RATIO:
DZ/MZ)
FOR SOME VARIABLES
Variable
F-ratio
P-value
Albumin a 1-Antitrypsin
5.30 2.59 4.47
4.85
IgA Peripheral blood Percentage lymphocytes
Fifteen twins of the 13 DZ pairs were anergic to PPD antigen compared to 15 twins among the 18 MZ pairs. The frequency of positive responses to mumps and Candida antigens was about 30% in both DZ and MZ pairs. In general there was a good correlation between the responses to the three antigens. The frequency of PPD anergic twins (48%) is only slightly lower than that of the age-matched controls (60%). The responses to mumps and Candida antigens were similar to those of controls. Accelerated ESR was associated with increased concentrations of IgM, IgG, haptoglobin, orosomucoid and (~~antitrypsin. Although the immunoglobulin concentrations were normal in most twins, low IgG was associated with a more severe form of IHD (r = 0.24; P < 0.035). Only those F-ratios reaching statistical significance are shown in Table 3. Discussion The present study shows no association between routine hematological and immunological tests and the degree of ischemic heart disease except for the association between low IgG levels and advanced ischemic heart disease. Twins with two or more positive skin tests were evenly distributed in the different ischemic heart disease groups. However, the whole group seems to have a slightly decreased response to PPD antigen as compared to the healthy age-matched controls. The immune and hematological status of this twin material has been determined by rather “crude methods” which does not exclude that there are certain differences in the immune status between patients with vascular disease and controls. Moreover, it is still possible that such alterations are associated with the degree of ischemic heart disease or peripheral vascular disease. More refined immunological procedures in patients with angiographically visualized coronary artery disease would facilitate the possibility of proving such a hypothesis. ECG and exercise testing represent a valuable non-invasive method for diagnosing myocardial ischemia and, by implication, the presence of coronary artery disease. It may therefore be anticipated that our classification of ischemic heart disease correlates fairly well with the presumed degree of coronary atherosclerosis [20]. In a recent study no significant differences between healthy controls and patients with proven vascular disease were found in PHA induced lymphocyte transformation [21]. However, these authors found significantly elevated IgM and IgG in patients with proven infarctions, a finding which is not supported by the results from this study. Differences in the time elapsed between the myocardial infarction and the time of the test may explain some of this discrepancy.
200
The significant F-ratios for IgA and the percentage of lymphocytes in the peripheral blood are rather interesting. It may be mentioned that lymphocytes of healthy controls show rather a high variation in their responses to different mitogens [2]. By studying the genetic determination of lymphocyte mitogen responses and other immunological tests it may be possible to define high, medium and low responders. Such a study in healthy MZ and DZ twins is in progress. In order to elucidate the relationship between hereditary and environmental factors in premature ageing with an increased susceptibility to develop ischemic heart disease, further integrated studies are needed. The question whether the development of ischemic heart disease is partly mediated by immunological mechanisms is still unanswered but the immunological derangement of some ischemic heart disease patients warrants further research in this field. References 1 Keys, A.. Dietary factors in atherosclerosis. In: H.T. Blumenthal (Ed.). Charles C. Thomas, Springfield, IL, 1967, pp. 576-622. 2 Davies, D.F., Hypothesis. An immunological view of atherogenesis, J. Atheroscler. Res.. 10 (1969) 253, 3 Bauer. H., Waters, T.J. and Talano, J.V., Antimyocardial antibodies in patients with coronary heart disease, Amer. Heart J., 83 (1972) 612. 4 Gerii, S., Szekely, J., Bihari-Varga, M., Szondy, E., Antibodies against vascular antigens I. In: G. Schettler and A. W&e1 (Eds.), Atherosclerosis III (Proc. 3rd Int. Symp.), Springer-Verlag. Berlin. 1974, PP. 591-594. 5 Watson, K.C. and Kerr, E.J.C., Functional role of cholesterol in infection and autoimmunity, Lancet. 1 (1975) 308. 6 F&t, G., Szondy, E., Szekely, J.. Nbnai, I. and Gerd, S., Studies on the occurrence of circulating immune complexes in vascular diseases, Atherosclerosis, 29 (1979) 181. 7 Howard, A.N., Pat&&i, J., Bowyer, D.E. and Gresham, G.A., Atherosclerosis induced in hypercholesterolemic baboons by immunological injury; and the effects of intravenous polyunsaturated phosphatidyl choline, Atherosclerosis, 14 (1971) 17. 8 Gallagher, P.J., Muir, C.A. and Taylor, T.G.. Immunological aspects of arterial disease, Atherosclerosis, 30 (1978) 361. 9 Dixon, F., The etiology and pathogenesis of murine systemic lupus erythematosus. In: 10th Annual Meeting of the Scandinavian Society for Immunology, Llllehammer, Norway, 1979. 10 Weksler, M.E. and Hiitteroth. T.H.. Impaired lymphocyte functions in aged humans. J. Clin. Invest., 53 (1974) 99. abnormalities and serum factors in 11 Helm, G., Bjijrkholm, M. and Mellstedt, M., Lymphocyte Hodgkin’s disease. In: R.H. Neubauer (Ed.). Naturally-Occurring Biological ImmunosUPPressiye Factors and Their Relationship to Disease, CRC Press, Florida, 1979, PP. 3-36. I2 Gnad, J.P., PaychCe, M., Cueves, M. and Fernandes, B., Cell-mediated immunity in an ageing PoPulation. Clin. Exp. Immunol.. 27 (1977) 85. 13 Burnet, F.M.. An immunological approach to ageing, Lancet, 2 (1970) 368. 14 Mathews. J.D., Whittingham. S. and Mackay, I.R., Autoimmune mechanisms in human vascular disease, Lancet. 2 (1974) 1423. 15 Cederlof, R., The Twin Method in Epidemiological Studies on Chronic Disease. Karolinska Institutet. Stockholm, 1966. 16 Liljefors, I.. Coronary heart disease in male twins - Hereditary and environmental factors in COnCordant and discordant palm, Acta Med. Scand. (Suppl.). (1970) 511. 17 Rose, G., The diagnoses of ischemic heart pain and intermittent claudication in field SuIveYs, Bull. WHO, 27 (1962) 645. 18 Laurell, A.B.. Quantitative estimation of proteins by electrophoresis, Anal. Biochem.. 15 (1966) 45. 19 Osborne. R.H. and deGeorge, F.V.. Genetic Basis of Morphological Variation, Harvard Universitv Press, Cambridge. MA, 1959. PP. 15-24. 20 Goldschlager, N.. Seizer, A. and Cohn, K.. Treadmill stress tests as indicators of Presence and Severity of coronary artery disease, Ann. Intern. Med., 85 (1976) 277. 21 Gray. M.V.. Hill, J.D. and Mitchell, J.R.A., Immune mechanism in patients with proven VasCUhU disease. Atherosclerosis, 31 (1978) 377. 22 Bjihkholm, M., Immunodeficiency in Hodgkin’s disease and its relation to prognosis. Stand. J. Haematol., Suppl. No. 33 (1978).
A tkerosclerosis,
36 (1980)
0 Elsevier/North-Holland
IMMUNOLOGIC DISEASE
195-200 Scientific
Publishers,
EVALUATION
Genetic
Determination
MAGNUS
BJGRKHOLM,
OF PATIENTS WITH ISCHEMIC HEART
and Relation
ULF
Ltd.
DE FAIRE
to Disease
and G6RAN
Department of Medicine, Seraphimer Hospital, Stockholm Immunology, Huddinge Hospital, Huddinge (Sweden) (Received 8 October, 1979) (Revised, received 29 December, (Accepted 8 January, 1980)
GOLM
’
and ’ Department
of Clinical
1979)
Summary Delayed skin hypersensitivity and serum immunoglobulins were studied in relation to the severity of ischemic heart disease in 18 male monozygotic and 13 male dizygotic twin pairs, aged 55-78 years. The twin pairs were selected from the Swedish Twin Registry. Low IgG was seen in patients with myocardial infarction and definitive angina pectoris. No correlation between skin anergy and the severity of ischemic heart disease was found. These findings may support the possibility that immunological mechanisms play a part in the pathogenesis of ischemic heart disease. Significant F-ratios for IgA and differential white cell count support a genetic determination of these variables. Key words:
Immunodeficiency
-Zschemic
heart disease - Twins
Introduction The etiology and development of atherosclerosis remain to a large extent unknown despite intense scientific efforts to elucidate this crucial issue. During the last decades most studies have been focused on abnormalities in the lipid metabolism especially that of cholesterol. However, advanced atherosclerosis can also be found in patients with normal or subnormal serum cholesterol levels [ 11. Since the late sixties some interest has been devoted to the immunological Please address reprint requests to: Dr Magnus BjGrkholm. Department of Medicine. Danderyd’s HosS-18288 Danderyd, Sweden.
Pital.
196
aspects of atherosclerosis [ 21. As the immune system is in direct contact with most tissues of the body, changes in the immunoreactivity may be expected to contribute to tissue damage in many organs. Autoantibodies against vascular antigens and antimyocardial antibodies have been demonstrated in patients with different vascular diseases [3,4]. It has been postulated that immune complexes play a central part in the development of arterial lesions [2,5,6]. Recent animal experiments support the hypothesis that antibodies to dietary proteins accelerate the development of atherosclerosis. The vascular changes may be mediated by immune complexes [7,8]. Moreover, myocardial infarction associated with coronary lesions are commonly present in mice with lupus syndrome [ 91. Atherosclerosis normally affects middle aged and elderly people. With increasing age immunological defects in cell mediated immunity develop in the normal population [ 10-121. It has been postulated that the normal immunological ageing may promote the development of atherosclerosis [13, 141. In the present study monozygotic and dizygotic twins, concordant and discordant with regard to ischemic heart disease, have been tested immunologically to determine whether evidence for immune alterations associated with underlying ischemic heart disease could be adduced. Moreover, the genetic determination of certain immunological and routine blood tests are presented. Materials and Methods Patient population The twin sample which derives from the Swedish Twin Registry [15] constitutes a follow-up of twin pairs earlier examined in 1967-1968 [ 161. It now consists of 31 male twin pairs, 18 monozygotic (MZ) and 13 dizygotic (DZ) aged 55-78 years (mean 66 years). These pairs had been selected by means of the angina pectoris questionnaire method according to Rose [ 171. Pairs judged to be concordant or discordant with regard to the probable presence of IHD at the examination in 1967-1968 were invited to a re-examination performed at Serafimerlasarettet. Controls The age-matched control material for delayed skin hypersensitivity consisted of 40 healthy persons from the laboratory and hospital staff and some of their parents.
TABLE 1 CLASSIFICATION
OF ISCHEMIC HEART DISEASE
Group 1: Myocardial infarction Group 2: Angina pectoris and ST-segment depressions > 0.5 mm at eXerCiSe. Group 3: (a) Angina pectoris without ST-segment depression > 0.5 mm at exercise. (b)no angina pectoris symptoms but ST-segment depressions > 0.5 mm at eXerCiSe. Group 4: Suspected angina pectoris without the above ECG changes. Group 5: None of the findings in groups l-4.
197
Classification
of IHD
The presence of IHD was established by means of the clinical history and electrocardiographic recordings at rest and during physical excercise. Various clinical manifestations of IHD were grouped according to a five-graded scale (Table 1) described by Liljefors [ 161. Patients in groups 1 and 2 had definite signs of ischemic heart disease, whereas those in groups 3-5 lacked these diagnostic criteria. Direct classification of the degree of coronary atherosclerosis by means of coronary angiography could not be performed for ethical reasons. Zygosity
determination
The zygosity diagnoses were based exclusively on diagnoses already made in 1967-1968, i.e. similarity questions, and in case of uncertainty on serologic determination which comprised the blood group systems ABO, MN, P, K, KE, FY, Ik and Rh and the serum groups Gn, Gc and Hp [ 161. Immunological
studies
Special attention was focused on the history of frequent infections, malignant tumors, hypersensitivity and autoimmune diseases among the patients and their relatives.
Delayed
skin hypersensitivity
All patients received intradermal injections of 0.1 ml mumps skin test antigen (Eli Lilly & Co, Indianapolis, U.S.A.) and Candida al&cans antigen (dermatophytin “O”, Hollister Stier Lab) on the volar surface of the right forearm. Purified protein derivate of tuberculin (2TU PPD, State Serum Institute, Copenhagen, Denmark) was injected on the volar surface of the left forearm. Skin reactions were evaluated after 48 h. A mean diameter of induration of 6 mm or more was considered positive. Immunoglobulins were quantitated by the rocket technique according to Laurel1 [ 181. Other tests
Hemoglobin concentration, WBC (including differential acute phase reactants were also determined.
counts), ESR and
Statistics
Intrapair variances for the different immunological and hematological measurements were calculated according to Osborne and deGeorge [19,for both MZ and DZ series. Ratios (F-ratios) between the intrapair variance for DZ and MZ series were calculated as well and tested for statistical significance by means of F-distribution. In order to test significance levels of differences between means, t-tests were used. As a measure of association for each pair of variables, Pearsons’ product moment correlation (r) has been chosen. Results Concordance and discordance for IHD The distribution of twin pairs with regard to severity of IHD is evident from
198
IHD Group 1
2
MZ
DZ
Partner
Partner
3
4
5
1
2
3
4
5
Fig. 1. Distribution of pairs according to IHD group. Numbers within circles denote pairs concordant for IHD group.
Fig. 1. Myocardial infarction (IHD group 1) was recorded in 9 of 18 MZ pairs and in 9 of 13 DZ pairs. In 3 of the MZ pairs both twins had had myocardial infarctions as compared to one of the DZ pairs. Concordance for the same IHD group was recorded in 6 MZ pairs and in only one DZ pair. Thus, 12 MZ pairs and 12 DZ pairs were discordant for the same IHD group. We could demonstrate no differences in the family histories of patients with IHD (groups 1 and 2) and without IHD (groups 3,4 and 5). Moreover, no common denominator with regard to IHD was found in the patients’ histories. The mean age of IHD patients was 67 years as compared to 65 years in patients without IHD (Table 2). The ability to respond to PPD, mumps and Candida antigens did not differ between the groups. The IgM and IgA concentrations, the Hb values and WBC counts were also comparable, but IgG was lower in groups 1 and 2 (Table 2).
TABLE 2 CLINICAL
VARIABLES
IN RELATION
TO IHD (mean f SD)
Variable
IHD l-2 (xl = 30)
Age (yr) Hb (gfl) WBC (X109/1) Total lymphocytes (X109/1) ESR (mm/l h) HaptogIobin (PP) aI-Antitrypsin (B/l) Albumin (g/l) IgG (g/1) IgM U/l) IgA (g/I) PPD Induration > 6 mm Mumps induration > 6 mm Candida induration > 6 mm
67 154 5.8 1.9 14 1.2 2.2 44 8.1 1.02 1.36 15 9 10
a NS = not significant.
P-value
IHD 3-5 (n = 32) * 5 * 17 * 2.2 * 1.0 * 14 f 0.6 * 0.5 + 3.6 + 2.0 + 0.64 + 0.78
65 153 5.3 1.7 12 1.2 2.2 45 10.1 1.00 1.51 15 10 9
* 7 * 12 * 1.7 * 0.8 * 12 + 0.6 * 0.4 * 4.3 * 1.9 + 0.40 * 0.74
NS a NS NS NS NS NS NS NS NS NS NS NS NS NS
199 TABLE 3 INTRAPAIR
VARIANCE
RATIOS
(F-RATIO:
DZ/MZ)
FOR SOME VARIABLES
Variable
F-ratio
P-value
Albumin a 1-Antitrypsin
5.30 2.59 4.47
4.85
IgA Peripheral blood Percentage lymphocytes
Fifteen twins of the 13 DZ pairs were anergic to PPD antigen compared to 15 twins among the 18 MZ pairs. The frequency of positive responses to mumps and Candida antigens was about 30% in both DZ and MZ pairs. In general there was a good correlation between the responses to the three antigens. The frequency of PPD anergic twins (48%) is only slightly lower than that of the age-matched controls (60%). The responses to mumps and Candida antigens were similar to those of controls. Accelerated ESR was associated with increased concentrations of IgM, IgG, haptoglobin, orosomucoid and (~~antitrypsin. Although the immunoglobulin concentrations were normal in most twins, low IgG was associated with a more severe form of IHD (r = 0.24; P < 0.035). Only those F-ratios reaching statistical significance are shown in Table 3. Discussion The present study shows no association between routine hematological and immunological tests and the degree of ischemic heart disease except for the association between low IgG levels and advanced ischemic heart disease. Twins with two or more positive skin tests were evenly distributed in the different ischemic heart disease groups. However, the whole group seems to have a slightly decreased response to PPD antigen as compared to the healthy age-matched controls. The immune and hematological status of this twin material has been determined by rather “crude methods” which does not exclude that there are certain differences in the immune status between patients with vascular disease and controls. Moreover, it is still possible that such alterations are associated with the degree of ischemic heart disease or peripheral vascular disease. More refined immunological procedures in patients with angiographically visualized coronary artery disease would facilitate the possibility of proving such a hypothesis. ECG and exercise testing represent a valuable non-invasive method for diagnosing myocardial ischemia and, by implication, the presence of coronary artery disease. It may therefore be anticipated that our classification of ischemic heart disease correlates fairly well with the presumed degree of coronary atherosclerosis [20]. In a recent study no significant differences between healthy controls and patients with proven vascular disease were found in PHA induced lymphocyte transformation [21]. However, these authors found significantly elevated IgM and IgG in patients with proven infarctions, a finding which is not supported by the results from this study. Differences in the time elapsed between the myocardial infarction and the time of the test may explain some of this discrepancy.
200
The significant F-ratios for IgA and the percentage of lymphocytes in the peripheral blood are rather interesting. It may be mentioned that lymphocytes of healthy controls show rather a high variation in their responses to different mitogens [2]. By studying the genetic determination of lymphocyte mitogen responses and other immunological tests it may be possible to define high, medium and low responders. Such a study in healthy MZ and DZ twins is in progress. In order to elucidate the relationship between hereditary and environmental factors in premature ageing with an increased susceptibility to develop ischemic heart disease, further integrated studies are needed. The question whether the development of ischemic heart disease is partly mediated by immunological mechanisms is still unanswered but the immunological derangement of some ischemic heart disease patients warrants further research in this field. References 1 Keys, A.. Dietary factors in atherosclerosis. In: H.T. Blumenthal (Ed.). Charles C. Thomas, Springfield, IL, 1967, pp. 576-622. 2 Davies, D.F., Hypothesis. An immunological view of atherogenesis, J. Atheroscler. Res.. 10 (1969) 253, 3 Bauer. H., Waters, T.J. and Talano, J.V., Antimyocardial antibodies in patients with coronary heart disease, Amer. Heart J., 83 (1972) 612. 4 Gerii, S., Szekely, J., Bihari-Varga, M., Szondy, E., Antibodies against vascular antigens I. In: G. Schettler and A. W&e1 (Eds.), Atherosclerosis III (Proc. 3rd Int. Symp.), Springer-Verlag. Berlin. 1974, PP. 591-594. 5 Watson, K.C. and Kerr, E.J.C., Functional role of cholesterol in infection and autoimmunity, Lancet. 1 (1975) 308. 6 F&t, G., Szondy, E., Szekely, J.. Nbnai, I. and Gerd, S., Studies on the occurrence of circulating immune complexes in vascular diseases, Atherosclerosis, 29 (1979) 181. 7 Howard, A.N., Pat&&i, J., Bowyer, D.E. and Gresham, G.A., Atherosclerosis induced in hypercholesterolemic baboons by immunological injury; and the effects of intravenous polyunsaturated phosphatidyl choline, Atherosclerosis, 14 (1971) 17. 8 Gallagher, P.J., Muir, C.A. and Taylor, T.G.. Immunological aspects of arterial disease, Atherosclerosis, 30 (1978) 361. 9 Dixon, F., The etiology and pathogenesis of murine systemic lupus erythematosus. In: 10th Annual Meeting of the Scandinavian Society for Immunology, Llllehammer, Norway, 1979. 10 Weksler, M.E. and Hiitteroth. T.H.. Impaired lymphocyte functions in aged humans. J. Clin. Invest., 53 (1974) 99. abnormalities and serum factors in 11 Helm, G., Bjijrkholm, M. and Mellstedt, M., Lymphocyte Hodgkin’s disease. In: R.H. Neubauer (Ed.). Naturally-Occurring Biological ImmunosUPPressiye Factors and Their Relationship to Disease, CRC Press, Florida, 1979, PP. 3-36. I2 Gnad, J.P., PaychCe, M., Cueves, M. and Fernandes, B., Cell-mediated immunity in an ageing PoPulation. Clin. Exp. Immunol.. 27 (1977) 85. 13 Burnet, F.M.. An immunological approach to ageing, Lancet, 2 (1970) 368. 14 Mathews. J.D., Whittingham. S. and Mackay, I.R., Autoimmune mechanisms in human vascular disease, Lancet. 2 (1974) 1423. 15 Cederlof, R., The Twin Method in Epidemiological Studies on Chronic Disease. Karolinska Institutet. Stockholm, 1966. 16 Liljefors, I.. Coronary heart disease in male twins - Hereditary and environmental factors in COnCordant and discordant palm, Acta Med. Scand. (Suppl.). (1970) 511. 17 Rose, G., The diagnoses of ischemic heart pain and intermittent claudication in field SuIveYs, Bull. WHO, 27 (1962) 645. 18 Laurell, A.B.. Quantitative estimation of proteins by electrophoresis, Anal. Biochem.. 15 (1966) 45. 19 Osborne. R.H. and deGeorge, F.V.. Genetic Basis of Morphological Variation, Harvard Universitv Press, Cambridge. MA, 1959. PP. 15-24. 20 Goldschlager, N.. Seizer, A. and Cohn, K.. Treadmill stress tests as indicators of Presence and Severity of coronary artery disease, Ann. Intern. Med., 85 (1976) 277. 21 Gray. M.V.. Hill, J.D. and Mitchell, J.R.A., Immune mechanism in patients with proven VasCUhU disease. Atherosclerosis, 31 (1978) 377. 22 Bjihkholm, M., Immunodeficiency in Hodgkin’s disease and its relation to prognosis. Stand. J. Haematol., Suppl. No. 33 (1978).