Collagen IV is a collagen present in all metazoan phyla. It is found in the basal lamina, where it takes the form of structural sheets in a crosslinked extracellular matrix. The collagen IV alpha-3 subunit (Col4A3) has been implicated as the target antigen in the autoimmune disease Goodpasture syndrome, and mutations in Collagen IV have been implicated in the hereditary Alport syndrome. In immunohistochemistry, antibodies to collagen IV react with basement membranes in a wide variety of tissues, including kidney, skin, striated and smooth muscle, spleen, lymph node, lung, placenta, and tendon. References: Biol Cell. 1996;88(1-2):37-44, PMID: 9175266; N Engl J Med. 2003; 348:2543-2556, DOI: 10.1056/NEJMra022296; Matrix Biol. 2017 Jan;57-58:45-54, PMID: 27576055;