Renal AREG expression is increased in human crescentic GN. AREG immunostaining (brown) of kidney biopsy specimens from (A) control patients, (B) patients with microscopic polyangiitis, and (C) patients with Goodpasture syndrome. Asterisks indicate areas of glomerular crescents, thin arrows indicate parietal epithelial cells, thick arrows indicate podocytes, and arrowheads indicate tubule cells.