Immunohistochemical localization of S protein/vitronectin in human atherosclerotic versus arteriosclerotic arteries.

The localization of S-protein/Vitronectin as deposits in arterial lesions and as a component of extracellular matrices was investigated by indirect immunofluorescence in ten atherosclerotic samples of carotid endarterectomy compared with ten arteriosclerotic temporal biopsies. Anti-C5b-9 neoantigens, anti-C3, anti-C3d, anti-H, anti-IgG and anti-IgM antibodies were applied on serial sections. In the atherosclerotic plaque, S-protein deposits were observed as irregular granules and spots in the fibrous cap and the internal part of the media at the vicinity of the plaque; they inconstantly colocalized with C5b-9 neoantigens. When present the SC5b-9 complexes were generally associated with cell remnants in the sclerotic matrix. In the temporal artery biopsies, S-protein was bound exclusively to the internal elastic lamina in association with C3d, but was absent from the intimal fibrous thickening. S-protein was not detected as a diffuse component of the extra-cellular matrix of either musculo-elastic or muscular medias, but was clearly demonstrated in smaller arteries; this result suggests a differential distribution of S-protein along the arterial tree.