Immunohistochemical evidence for the presence of collagen type III in human arterial walls, arterial thrombi, and in leukocytes, incubated with collagen in vitro.

Sections of arterial walls and of thrombi and smears of leukocytes previously incubated in vitro with collagen type III were examined by immunohistochemical technique for the presence of collagen types I, II and III. In arterial walls collagen type III was detected immediately underlaying the endothelial cell layer and in the tissue between tunica elastica interna and adventitia. Collagen type I was not shown in the subendothelial layer. Fresh thrombi contained occasionally collagen, but only of type III. This was associated with leukocytes. Leukocytes were capable in vitro to associate and/or phagocytose collagen type III and this could be visualized immunohistochemically. The data show that collagen type III in vivo may play a crucial role in the initiation of thrombus formation.