[Erythema elevatum diutinum. II. Immunoelectronmicroscopical study of leukocytoclastic vasculitis within the intracutaneous test reaction induced by streptococcal antigen (author's transl)].

A leukocytoclastic vasculitis was induced by intracutaneous injection of streptococcal antigen in a patient with erythema elevatum diutinum (E.e.d.). The immunoelectronmicroscopical demonstration of C3 was performed by use of the peroxidase-antiperoxidase multistep technique 24 h after the injection of the antigen. Deposits of C3 were found between endothelial cells, on the outer surface of endothelial cells, pericytes, and smooth muscle cells, as well as within the multilayered basal lamina of small vessels. Intact and disintegrating neutrophils accumulate within the vessel walls and in their surroundings. Necrosis and fibrin deposition are present in advanced stages. The findings demonstrate the sequence of events in leukocytoclastic vasculitis at the ultrastructural level. They also support the hypothesis that in E.e.d. an Arthus type reaction induced by bacterial antigens may be of pathogenetic significance.