Bovine T cells do not require auxiliary cells for response to selected mitogens

Bovine peripheral blood mononuclear cells (PBM's) were depleted of monocytes by three techniques: plastic adherence, passage through Sephadex G-10, and carbonyl iron treatment followed by buoyant density separation over Ficoll-Hypaque (FH). Although the resulting cell populations differed in their T and B cell ratios and percentages of residual monocytes, these preparations were generally more responsive to phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM) than control cells containing monocytes. Passage of PBM's over a column of Sephadex G-10 and subsequent negative selection on plastic dishes previously coated with F(ab′) 2 anti-immunoglobulin or peanut agglutinin (PNA) resulted in highly enriched populations of T cells bearing receptors for PNA (99% PNAR +) and B cells (84% surface-immunoglobulin +, 10% PNAR +, 6% null), respectively. The percentage of monocytes remaining in either cell preparation was less than 0.1%. Reactions of these isolated lymphocyte subpopulations demonstrated that bovine T cells can be strongly activated by PHA, Con A and PWM without apparent need for auxiliary B cells or monocytes. Stimulation of T and B cell populations with PWM produced a pattern of reactivity which was interpreted to indicate that PWM may also activate B cells slightly, perhaps requiring T cell help. The use of this simple panning technique for lymphocyte separation, with its large capacity and specificity, has general application to the further study of cellular interactions.