Effect of in vitro selenium repletion on bovine lymphocyte proliferation

Abstract

Deficient or toxic levels of selenium (Se) are known to impair immune function. Peripheral blood mononuclear cells (PBMC) were isolated from Holstein heifers of adequate Se status. PBMC were plated at densities of 0.5, 1.0, and 2.0 × 10 5 cells/well in 96-well microtiter plates and stimulated with T-cell mitogens, concanavalin A (ConA) and phytohemagglutinin-P (PHAP), and pokeweed mitogen (PWM), a T-dependent B-cell mitogen. Sera incorporated into the incubation system were from two newborn calves born to Se-deficient dams and averaged 20 ng Se/ml. Se additions of 50-400 ng/ml resulted in significant enhancement of PWM-stimulated proliferation relative to controls (no added Se). Enhancement of proliferation was cell density dependent, occurring predominately at a density of 0.5 × 10 5 cells/well. In contrast, proliferative responses of PBMC to ConA and PHAP were generally not enhanced by repletion with the lower levels of Se. Supplementation with higher levels of Se (1600–3200 ng/ml) inhibited proliferative responses to all mitogens tested regardless of cell density in culture. In summary, repletion with physiological levels of Se selectively stimulated B-cell proliferation an effect which was dependent on cell density.