PROLIFERATION AND PHENOTYPE OF BOVINE MONONUCLEAR LEUKOCYTES IN CULTURES STIMULATED BY POKEWEED MITOGEN

Cell proliferation and phenotype were evaluated at 2, 4, 6, 8, 10, 12, and 14 d in cultures of bovine peripheral blood mononuclear leukocyte s stimulated by pokeweed mitogen. Cell numbers in unstimulated and sti mulated 2-d cultures decreased to about 45% of the number originally a dded. Cell numbers at 6 d in stimulated cultures increased to 96% of t he number originally seeded and remained elevated from 6 to 14 d in cu ltures. In contrast, numbers in unstimulated cultures at 4 to 14 d dec reased; <20% of the original number remained at 14 d. The increase in cell numbers in stimulated cultures from 4 and 6 d was due primarily t o an increase in CD2(+) T cells, specifically the CD4(+) T-cell subset . Proliferation of interleukin-2 receptor(+) and major histocompatibil ity class II antigen(+) cells increased in these cultures. Expression of these antigens decreased in unstimulated cultures. The B-cell numbe rs in stimulated cultures at 2 to 4 d increased and then stabilized. C oncentrations of IgM in stimulated 14-d cultures were 5 to 15 times th ose in parallel unstimulated cultures. Overall, IgM secretion induced by pokeweed mitogen by B cells in cultures of bovine mononuclear leuko cyte is associated with proliferation of CD4(+) (helper-inducer) T cel ls, B cells, and increased expression of activation antigens.