361
Atherosclerosis, 30 (1978) 361-363 @ Elsevier/North-Holland Scientific Publishers, Ltd.
Letter
to the Editors
IMMUNOLOGICAL
ASPECTS OF ARTERIAL
DISEASE
Sirs : The paper by Fiist et al. on the occurrence of circulatory immune complexes in vascular disease published in your journal [Atherosclerosis, 29 (1978) 1811 prompts us to draw attention to some work we have been carrying out on the role of dietary antigens in the development of arterial disease in rabbits [Proc. Nutr. Sot., 36 (1977) 95A], the pathology of which has not yet been published. Howard et al. [Atherosclerosis, 14 (1971) 171 have shown that atherosclerosis develops more rapidly in animals injected with foreign proteins than in uninjetted controls and we were interested in the possibility that an immunological I reaction provoked by dietary antigens might induce a similar response. In this experiment, high fat diets containing either Promine D (PD), a soya bean protein known to be antigenic in calves [Smith and Sissons, Brit. J. Nutr., 33 (1975) 3291 or Promosoy 100 (P-100), a soya protein of low antigenicity, were fed to weanling New Zealand white rabbits for 11 months. These two protein sources were fed in conjunction with 190 g/kg of both maize oil (MO) and coconut oil (CO) in a 2 X 2 factorial experiment with 4 rabbits per treatment. At termination, aortas were stained with Sudan Black arid scored visually for atherosclerosis using the l-5 system of King and Royale [Cardiovasc. Res., 6 (1972) 627 J. Paraffin sections of renal and carotid arteries were prepared and Oil Red O-stained frozen sections of arteries were examined from a small number of animals with high aorta scores. Two animals registered aorta scores of 5, ten had scores of 3 or 4 and four (three of which were fed on Promosoy 100 and corn oil) scored 1 or 2. All the animals developed antibodies to soya proteins and the ones with the highest titres showed the most severe arteriosclerosis. There was no correlation between plasma cholesterol values and antibody titres but both plasma cholesterol and triglyceride levels were significantly correlated with aorta score (r = +0.54 and +0.56, respectively, P < 0.05). Microscopic changes were present in either the aorta or arteries of all animals with a score of 3 or more. Chief features were intimal thickening, medial calcification and fragmentation of elastic lamellae. Intimal thickening was most pronounced in the arteries and generally was in the range of 25-100% of the thickness of the medial muscle. Calcification was more extensive in the aorta. Neither cholesterol clefts nor significant numbers of foamy macrophages were identified. In 8 animals (3 in the MO-PD, 3 in the CO-PD and 2 in the CO-P-100 group) significant numbers of chronic inflammatory cells were present in either renal
362
or carotid arteries. Lymphocytes and macrophages w$ere clearly recognised but plasma cells, eosinophils and polymorphs were absent. In 4 of these animals there were appreciable numbers of giant cells. These were centred around both internal and external elastic lamellae, often in association with disrupted fragments of elastin (see Fig. 1). A single cluster of giant cells was seen in each of two additional rabbits. These features were strongly reminiscent of human giant cell arteritis. There was no evidence in any of the arterial or aortic sections of a necrotising arteritis or thrombus formation. We feel that our results support the hypothesis that antibodies to dietary proteins accelerate the development of atherosclerosis in rabbits. Soluble immune complexes may well be responsible, presumably initiating the vascular damage by adhering to the endothelial lining and inducing the release of histamine after complement fixation. The presence of a chronic inflammatory arteritis is certainly in keeping with an immune complex-mediated disease, although the close association of the inflammatory infiltrate with fragmented elastica raises the possibility that the damage was mediated by a direct cytotoxic reaction directed against some component of elastin. Robert et al. [Atherosclerosis, 13 (1971) 4271, for example, have produced atherosclerosis in rabbits by prolonged immunisation with elastin-rich extracts of human and porcine aortic wall. We are now repeating broadly similar experiments on a larger scale in an attempt to answer some of the questions raised by the preliminary work: immune complexes have been detected in the sera of all the soya-fed rabbits at some stage of the experiment. Animals fed on low-fat soya diets are included in
Fig. 1. Rabbit renal artery (CO-PD diet) showing moderate intimal thickening (i) and inflammatory cell infiltration with prominent giant cells (starred) in close association with fragmented internal and external elastic lamella (arrowed). H and E. X 360.
363
these experiments, while other rabbits are being given high-fat diets containing milk proteins in place of soya proteins. Faculty of Medicine, University of Southampton, Bassett Crescent East, Southampton SO9 3TU (Great Britain) (Received 26 May, 1978) (Accepted 30 May, 1978)
P.J. Gallagher Carol A. Muir T.G. Taylor
Atherosclerosis, 30 (1978) 361-363 @ Elsevier/North-Holland Scientific Publishers, Ltd.
Letter
to the Editors
IMMUNOLOGICAL
ASPECTS OF ARTERIAL
DISEASE
Sirs : The paper by Fiist et al. on the occurrence of circulatory immune complexes in vascular disease published in your journal [Atherosclerosis, 29 (1978) 1811 prompts us to draw attention to some work we have been carrying out on the role of dietary antigens in the development of arterial disease in rabbits [Proc. Nutr. Sot., 36 (1977) 95A], the pathology of which has not yet been published. Howard et al. [Atherosclerosis, 14 (1971) 171 have shown that atherosclerosis develops more rapidly in animals injected with foreign proteins than in uninjetted controls and we were interested in the possibility that an immunological I reaction provoked by dietary antigens might induce a similar response. In this experiment, high fat diets containing either Promine D (PD), a soya bean protein known to be antigenic in calves [Smith and Sissons, Brit. J. Nutr., 33 (1975) 3291 or Promosoy 100 (P-100), a soya protein of low antigenicity, were fed to weanling New Zealand white rabbits for 11 months. These two protein sources were fed in conjunction with 190 g/kg of both maize oil (MO) and coconut oil (CO) in a 2 X 2 factorial experiment with 4 rabbits per treatment. At termination, aortas were stained with Sudan Black arid scored visually for atherosclerosis using the l-5 system of King and Royale [Cardiovasc. Res., 6 (1972) 627 J. Paraffin sections of renal and carotid arteries were prepared and Oil Red O-stained frozen sections of arteries were examined from a small number of animals with high aorta scores. Two animals registered aorta scores of 5, ten had scores of 3 or 4 and four (three of which were fed on Promosoy 100 and corn oil) scored 1 or 2. All the animals developed antibodies to soya proteins and the ones with the highest titres showed the most severe arteriosclerosis. There was no correlation between plasma cholesterol values and antibody titres but both plasma cholesterol and triglyceride levels were significantly correlated with aorta score (r = +0.54 and +0.56, respectively, P < 0.05). Microscopic changes were present in either the aorta or arteries of all animals with a score of 3 or more. Chief features were intimal thickening, medial calcification and fragmentation of elastic lamellae. Intimal thickening was most pronounced in the arteries and generally was in the range of 25-100% of the thickness of the medial muscle. Calcification was more extensive in the aorta. Neither cholesterol clefts nor significant numbers of foamy macrophages were identified. In 8 animals (3 in the MO-PD, 3 in the CO-PD and 2 in the CO-P-100 group) significant numbers of chronic inflammatory cells were present in either renal
362
or carotid arteries. Lymphocytes and macrophages w$ere clearly recognised but plasma cells, eosinophils and polymorphs were absent. In 4 of these animals there were appreciable numbers of giant cells. These were centred around both internal and external elastic lamellae, often in association with disrupted fragments of elastin (see Fig. 1). A single cluster of giant cells was seen in each of two additional rabbits. These features were strongly reminiscent of human giant cell arteritis. There was no evidence in any of the arterial or aortic sections of a necrotising arteritis or thrombus formation. We feel that our results support the hypothesis that antibodies to dietary proteins accelerate the development of atherosclerosis in rabbits. Soluble immune complexes may well be responsible, presumably initiating the vascular damage by adhering to the endothelial lining and inducing the release of histamine after complement fixation. The presence of a chronic inflammatory arteritis is certainly in keeping with an immune complex-mediated disease, although the close association of the inflammatory infiltrate with fragmented elastica raises the possibility that the damage was mediated by a direct cytotoxic reaction directed against some component of elastin. Robert et al. [Atherosclerosis, 13 (1971) 4271, for example, have produced atherosclerosis in rabbits by prolonged immunisation with elastin-rich extracts of human and porcine aortic wall. We are now repeating broadly similar experiments on a larger scale in an attempt to answer some of the questions raised by the preliminary work: immune complexes have been detected in the sera of all the soya-fed rabbits at some stage of the experiment. Animals fed on low-fat soya diets are included in
Fig. 1. Rabbit renal artery (CO-PD diet) showing moderate intimal thickening (i) and inflammatory cell infiltration with prominent giant cells (starred) in close association with fragmented internal and external elastic lamella (arrowed). H and E. X 360.
363
these experiments, while other rabbits are being given high-fat diets containing milk proteins in place of soya proteins. Faculty of Medicine, University of Southampton, Bassett Crescent East, Southampton SO9 3TU (Great Britain) (Received 26 May, 1978) (Accepted 30 May, 1978)
P.J. Gallagher Carol A. Muir T.G. Taylor
