Immunochemical study on basement membrane (type IV) collagens.

Basement membrane (type IV) collagens were extracted from a mouse tumour with acetic acid and from human placenta after limited enzymatic digestion. Antisera were produced against both collagens in rabbits and guinea-pigs and examined by various assays. These antisera were found to be specific for basement membrane collagen and showed little or no cross-reactions with the interstitial collagens, types I, II and III or with human placenta collagen consisting of alpha A and alpha B chains. Varying degrees of cross-reaction were observed between antisera to human and mouse type IV collagen. Immunochemical analyses demonstrated the presence of three distinct determinants in the tumour type IV collagen. Rabbit antisera against this antigen reacted with either collagenase-resistant segments or with a collagenous, disulphide-bonded segment (P3). Guinea-pig antisera recognized primarily antigenic determinants in the P3 segment. Antisera to placenta type IV collagen reacted with another collagenous, pepsin fragment (P1) which lacks disulphide bonds. These antisera showed complete cross-reaction with collagenous alpha 1 (IV) chains prepared from pepsin-digests of human placenta and bovine lens capsule.