Proliferative responses and IL-2 production by mononuclear cells from bovine mammary secretions, and the effect of mammary secretions on peripheral blood lymphocytes.

Mammary gland mononuclear cells (MGM) were compared with peripheral blood mononuclear cells (PBM) for their ability to proliferate in response to phytohaemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM), and to produce interleukin-2 (IL-2) when cultured with Con A. MGM proliferative responses to all three mitogens were at a level only just above background. Following removal of adherent cells by passage of the MGM population over Sephadex G10, their ability to proliferate increased but these responses were still significantly lower (P less than 0.001) than those of PBM. Mammary secretions from non-lactating cows and colostrum, but not milk, were found to suppress the proliferative responses to PHA and Con A of PBM following a 24-hr preincubation period. There was no difference in IL-2 production in response to Con A by Sephadex G10-treated MGM and PBM, and dry-cow secretions had no effect on IL-2 production.