Are antineutrophil cytoplasmic antibodies pathogenic? Experimental approaches to understand the antineutrophil cytoplasmic antibody phenomenon.

Antineutrophil cytoplasmic antibodies (ANCA) directed against the neutrophil enzymes PR3 and MPO are tightly associated with the development of small vessel vasculitis. This article reviews the large body of data derived from in vitro experiments documenting many different proinflammatory effects of these ANCA on neutrophils, monocytes, and endothelial cells. Taken in conjunction with clinical observations and data from animal models, a concept of the pathogenicity of ANCA emerges.