A demonstration of human beta-2-microglobulin specific association with the surface of teleostean cells

Purified human Beta-2 microglobulin (beta 2m) and a human beta 2m fluorochrome conjugate were used in exchange reactions to demonstrate that beta 2m associates with a teleostean cell surface protein. beta 2m exchange among brown bullhead, channel catfish, fathead minnow, and rainbow trout cells lines was detected by using either radioimmunoassay or flow cytometry. Evidence that beta 2m binds specifically with the surface of teleostean cells and possibly associates with an expressed class I MHC homologue is provided. Moreover, following exchange on brown bullhead cells, a coprecipitated protein of 45 kDa was observed following subsequent immunoprecipitation with the human beta 2m specific antibody B1.1G6. Given that beta 2m is a peripheral protein which has been shown to exchange with MHC expressing cells from different species, co-precipitation results suggest that the 45 kDa protein may represent a class I MHC homologue.