This project is designed to investigate the etiology and pathogenesis of idiopathic systemic vasculitis. This is a poorly-defined syndrome where vascular inflammation occurs in many organs, including skin and kidneys. Because of animal studies, it is presumably due to antigen-antibody complexes. Our studies are designed to identify antigen-antibody complexes in skin, blood and kidneys, and to study the development of spontaneous and induced vasculitis lesions by light and electron microscopy.