Immunoelectronmicroscopic examination of early lesions in histamine induced immune complex vasculitis in man.

In 4 cases of allergic vasculitis circulating immune complexes (IC) were demonstrated. Spontaneous and histamine induced vascular changes were studied by immunofluorescence microscopy. The early events in IC vasculitis were investigated at the ultrastructural level by immunoelectronmicroscopy using the peroxidase-antiperoxidase multistep technique. Our findings support the concept that human IC vasculitis is triggered by the deposition of circulating IC in the walls of postcapillary venules between endothelial cells, pericytes and the layers of the basal lamina. Tissue destruction is only secondary due to local complement activation and the release of lysosomal enzymes from chemotactically attracted leukocytes.