Indications for a distinct putative T cell population in mucosal tissue of carp (Cyprinus carpio L.)

A monoclonal antibody against carp intestinal T cells (WCL38; of IgM class) was produced by immunization of mice with isolated membrane molecules of carp intestinal intraepithelial lymphoid cells. Flow cytometric analysis showed that WCL38 reacted with 50-70% of the lymphoid cells isolated from intestine, gills or skin, with less than 6% of lymphoid cells isolated from thymus, head kidney or spleen and with a negligible number of PBL. WCL38+ cells were abundant in the intestinal epithelium and less numerous in the lamina propria. Immunogold labelling confirmed that WCL38 reacted with lymphoid cells; in gills and skin some of them have the morphology of large granular lymphoid cells. Immunochemical analysis showed that WCL38 reacted with dimeric membrane molecule on mucosal lymphoid cells with an Mr of 76 kDa, consisting of two 38 kDa subunits. WCL 38+ lymphoid cells are postulated to T cells, since WCL38 does not react with B cells, macrophages or non-specific cytotoxic cells. In conclusion, like higher vertebrates, carp seem to have a distinct (Putative) T cell population in their mucosal tissues.