MITOGEN AND ANTIGEN-INDUCED B-CELL AND T-CELL RESPONSES OF PERIPHERAL-BLOOD MONONUCLEAR-CELLS FROM THE HARBOR SEAL (PHOCA-VITULINA)

In vitro assays were developed for studies concerning the functioning of the immune system of the harbour seal (Phoca vitulina). Proliferati ve responses of peripheral blood mononuclear cells (PBMC) were measure d after stimulation with different concentrations of the mitogens conc anavalin A (Con A), pokeweed mitogen (PWM), phytohaemagglutinin (PHA) or lipopolysaccharide from Salmonella typhimurium (LPS). Con A and PWM induced strong proliferative responses, while PHA and LPS induced com paratively low proliferative responses. Responses of mitogen stimulate d PBMC to recombinant human interleukin-2 (rhIL-2) and in vitro immuno globulin production by mitogen stimulated PBMC were measured to discri minate between stimulation of T cells and B cells. It was found that C on A and PHA stimulate phocine T cells, PWM stimulates both T cells an d B cells and LPS predominantly stimulates phocine B cells. Antigen-sp ecific immune responses were measured after immunization of seals with an inactivated rabies vaccine and/or with tetanus toxoid. Antigen-spe cific proliferation of PBMC and the presence of antigen-specific antib ody forming cells were demonstrated for both antigens in the PBMC of i mmunized animals. The responses measured in vitro correlated well with the development of specific serum antibody titers to these antigens.