The basic concepts, associated with the role of humoral immunity to infectious diseases in marine pinnipeds will be discussed. Development of circulating IgG and IgM have been evaluated in the Northern Fur Seal from in utero to age 4 mos. The data indicate that these animals are not competent immunologically at birth but are competent when they leave the rookery. The significance of these findings for effective husbandry will be discussed.

California sea lion peripheral lymphocytes were stimulated to a relatively high degree by Concanavalin A (av. 47.45), less by phytohemagglutinin (av. 27.5) and very little by lipopolysaccharide (av. 2.6). Further, specific B-cell response to protein antigens was demonstrated, as was Fc receptors on polymorphs and monocytes. Current studies are directed towards production of bactericidal antibodies against bacterial polysaccharides. Preliminary data indicate that a dosage of 70 µg in three injections produce very high cidal antibody titers.