Ultrastructural studies of rat arteriosclerosis induced by stimulation of the immune system with ovalbumin

Intimal thickening in the aorta and carotid artery of rats was induced by repeated intraperitoneal injections of ovalbumin, 2.5 mg/kg BW, given weekly 5 times after initial subcutaneous sensitization, and/or feeding with a cholesterol-rich diet. The intimal thickening was apparent in immune-challenged rats fed with either a cholesterol-rich or a basal diet (p less than 0.01), whereas it was mild in non-immunized rats fed a cholesterol-rich diet. The ultrastructural changes in the thickened intima were characterized by leukocytic (mainly monocytic) adhesion and migration, and minor endothelial cell damage. Morphometric evaluation of leukocyte adhesion to the intima of the thoracic aorta revealed that the immunized rats fed either a cholesterol-rich or a basal diet showed greater leukocytic adhesion (p less than 0.01 and p less than 0.001, respectively) than that in non-immunized rats fed a cholesterol-rich diet, which in turn also showed an increased degree of leukocyte adhesion (p less than 0.05) than control rats. This immunological approach to the arteriosclerotic process could explain the earlier and more severe arteriosclerosis found in patients with immunological disorders, and the development of arteriosclerosis in the absence of hypercholesterolemia, hypertension and other risk factors.