Morphology

The morphologic consequences of immune complex injury are dominated by acute necrotizing vasculitis, with deposits of fibrinoid and intense neutrophilic exudation permeating the entire arterial wall. Affected glomerull are hypercellular because of swelling and proliferation of endothelial and mesangial cells, accompanied by neutrophilic and monocytic infiltration. The complexes can be seen on immunofluoresence microscopy as granular lumpy deposits of immunoglobulin and complement and on electron microscopy as electron dense deposits along the glomerular basement membrane.