In VitroModulation of Function, Proliferation, and Phenotype of Bovine Mononuclear Leukocytes by 13-Cis Retinoic Acid

13-cis retinoic acid at 10-9 and 10-8 M enhanced IgM secretion by pokeweed mitogen-stimulated bovine peripheral blood mononuclear leukocytes. Based on these data, effects of 10-8 mol/L of 13-cis retinoic acid on the proliferation and phenotype of bovine peripheral blood mononuclear leukocytes were evaluated. Cells from 2- to 14-d control and treated cultures were counted and their phenotype determined using monoclonal antibodies to bovine leukocyte surface antigens. A time-dependent decrease in cell numbers in resting cultures was unaffected by 13-cis retinoic acid. Cellular composition of resting cultures was also unaffected by 13-cis retinoic acid. In contrast, cell proliferation in 6-, 10- and 14-d poke-weed mitogen-stimulated cultures was suppressed but not abrogated by 13-cis retinoic acid treatment. Percentages of leukocyte subsets in pokeweed mitogen-stimulated cultures was affected negligibly by 13-cis retinoic acid. In contrast, actual numbers of CD2+ and CD4+ T-cells, and interleukin-2 receptor+ and major histocompatibility complex class II antigen+ cells in pokeweed mitogen-stimulated cultures was reduced by 13-cis retinoic acid. These findings suggest that retinoic acid modulates the B-cell function through its effects on the proliferation and differentiation of subsets.