CHARACTERIZATION OF A MONOCLONAL-ANTIBODY THAT RECOGNIZES A LYMPHOCYTE SURFACE-ANTIGEN FOR THE CETACEAN HOMOLOG TO CD45R

As part of our current efforts to develop assays and reagents to study the immune system of marine mammals, and in view of the effort curren tly made to develop monoclonal antibodies to cell surface proteins of lymphocyte subsets in different species, the present paper reports on the characterization of a monoclonal antibody against the homologue of CD45R on cetacean lymphocytes. The specificity of this antibody has b een characterized on the basis of immunoprecipitation of the antigen i t recognized, immunoperoxidase staining on cetacean lymph node and thy mus sections, as well as one and two-colour flow cytometric analysis o f cetacean peripheral blood mononuclear cells and single-cell suspensi ons of thymus, lymph node and spleen. Anti-cetacean CD45R (F21.H) immu noprecipitated proteins of 180, 200 and 220 x 10(3) MW, with the 180 x 10(3) MW form being predominantly expressed on T cells and the 220 x 10(3) MW form expressed predominantly on B cells and thymocytes. F21.H labelled all B cells and a proportion of T cells on single-cell suspe nsions of spleen cells. CD45R(-) killer whale peripheral blood lymphoc ytes expressed a higher density of CD2 than CD45R(+), a characteristic of memory T cells. Killer whale T lymphocytes also lost the expressio n of CD45R upon activation with concanavalin A (Con A) and phytohaemag glutinin (PHA). This is the first report of a monoclonal antibody to C D45R in cetaceans, and this antibody is foreseen as a possible valuabl e diagnostic and research tool to assess immune functions of captive a nd wild cetaceans as part of the evaluation of their health status.