Phylogeny of lymphocyte heterogeneity: identification and separation of functionally distinct subpopulations of channel catfish lymphocytes with monoclonal antibodies.

The purpose of this study was to identify monoclonal antibodies reactive with channel catfish T cells. Since a variety of commercially available anti-human and mouse T cell reagents failed to react with channel catfish leucocytes, the development of anti-fish T cell monoclonal antibodies was undertaken. One of these reagents, designated mAb 13C10, reacted with channel catfish surface immunoglobulin negative, but not positive, lymphocytes. This reagent, when used in "panning" protocols, was able to isolate those channel catfish lymphocytes which provide helper activity for antibody synthesis to a thymus dependent antigen. In addition, this antibody was observed to react with most thymocytes, neutrophils, and thrombocytes, few hepatocytes, and with some brain cells (possibly neurons). It was concluded that this antibody reacts with relatively high molecular weight antigens on channel catfish T cells and that it may be a pan anti-T cell reagent (possibly akin to Thy-2) for this species.