Steller sea lion (Eumetopias jubatus) pups undergo a decrease in circulating white blood cells and the ability of T...

Postnatal changes in circulating immune components and peripheral blood mononuclear cell (PBMC) proliferation were assessed in Steller sea lion pups (SSL; Eumetopias jubatus). Blood samples were collected for complete blood cell counts including total and differential white blood cell (WBC) counts from 46 pups ranging in age from 5 to 38 days old. Total WBC and neutrophil counts decreased in association with increased age of the pups. The ability of PBMC to proliferate was assessed by in vitro exposure to concanavalin A (ConA) or lipopolysaccharide (LPS) in 21 pups ranging in age from 7 to 32 days old. All SSL pups responded to in vitro stimulation with ConA and LPS 055:B5 indicating peripheral T and B cells are capable of responding to an antigenic challenge. ConA-induced T cell proliferation decreased with age while there was no change in spontaneous proliferation of PBMC or B cells exposed to LPS. The decreases in total WBC, neutrophil counts and T cell proliferation indicates that SSL undergo a period of postnatal development in cell-mediated immune function which is comparatively longer than phocid pups and consistent with other otariids.