PARTICIPATION OF T-LYMPHOCYTES IN ATHEROGENESIS - SEQUENTIAL AND QUANTITATIVE OBSERVATION OF AORTIC LESIONS OF RATS WITH DIET-INDUCED HYPERCHOLESTEROLEMIA USING EN FACE DOUBLE IMMUNOSTAINING

Using en face double immunostaining coupled with electron microscopy, we studied the temporal and spatial distribution of T lymphocytes and macrophages during the development of atherosclerosis in a diet-induce d rat model fed an atherogenic diet for 2-40 weeks. T lymphocytes and macrophages adhered to the aortic surface by 2 weeks on the diet, with subsequent migration under the endothelium, and formed a fatty streak -like lesion. Analysis of the cellular components revealed that infilt ration of T lymphocytes was most prominent in the incipient phase of l esion formation accounting for 60%, 29% and 34% of mononuclear cells a ppearing in 2-week lesions of the superior thoracic, inferior thoracic and abdominal segments of the aorta, respectively. After the incipien t phase, the relative number of T lymphocytes in the three segments of the aorta showed a slow decline; the proportion of T lymphocytes to m acrophages was approximately 1:3 to 1:4 in 10- to 20-week lesions. An overall view of the lesional cells often demonstrated direct cellular contact between T lymphocytes and macrophages. Further, OX6/ED1 double immunostaining demonstrated that Ia antigen was expressed on most mac rophages. In later stages, breakdown of foamy macrophages occurred, an d the extracellular accumulation of lipids and cell debris became prom inent. The results demonstrated that in the diet-induced rat model, to gether with macrophages, large numbers of T lymphocytes participated i n all stages of aortic lesions, initially adhering to the surface at p relesional stages and later as the principal component of the atherosc lerotic lesion. It is possible that the method described here will pro vide a good tool for examining the role of T lymphocytes in atherogene sis.