Potentiation of lymphocyte mitogenic responses to concanavalin A by antigen-activated peripheral blood monocytes

Purified protein derivative (PPD)-stimulated monocytes derived from Mycobacterium bovis-sensitized cattle significantly potentiated lymphocyte mitogenic responses to concanavalin A (conA), as measured by incorporation of [3H] thymidine into cellular DNA. Monocytes were cultured for 24 hours in the presence of PPD, washed thoroughly, and mixed with purified lymphocytes; various doses of conA were added to these cultures, and the cultures were incubated for 4 days and assayed for DNA synthesis. The lymphocyte mitogenic responses to suboptimal, buy not optimal, doses of conA were significantly enhanced by the presence of PPD-activated monocytes from M bovis-sensitized cattle. Treatment nonsensitized cattle with PPD did not result in any significant enhancement of conA-induced lymphocyte mitogenic responses at any dose of conA tested.