Inhibition of cytotoxic activity of carp lymphocytes (Cyprinus carpio) by anti-thymocyte monoclonal antibodies.

A series of monoclonal antibodies (mAbs) were developed against carp thymocytes and carp immunoglobulin (IgM). Anti-thymocyte mAbs reacted with thymocytes, head kidney lymphocytes (HKL) as well as peripheral blood lymphocytes (PBL) at various proportions. Anti-IgM antibody reacted with HKL and PBL but not with thymocytes. PBL from carp immunized with xenogeneic mouse myeloma cells exhibited cytotoxic activity against target cells but PBL from unimmunized fish showed weak cytotoxicity. Treatment of PBL with anti-thymocyte mAbs and guinea pig complement suppressed the cytotoxic activity dose dependently; however, anti-IgM mAb did not. These results indicate the cytotoxic cells in PBL possess cell surface antigens common to thymocytes.