Cellular interactions in the generation of bovine Con A-suppressor cells and in the mitogenic proliferative response.

Previously we have shown that macrophages acted as accessory cells for the induction of bovine suppressor cells with concanavalin A (Con A) and in mitogen induced lymphocyte proliferation. In exploration of possible mechanisms for the lymphocyte-macrophage interaction, it was found that the requirement for macrophages could not be substituted for with 2-mercaptoethanol. Furthermore, direct contact between lymphocytes and macrophages was necessary for optimal generation of suppressor cells. However, de novo protein synthesis by macrophages or lymphocytes apparently was not essential for the induction of Con A suppressor cells. For generation of suppressor cells, Con A had to be present in a soluble form during the entire induction period, as mitogen "pulsing" of either lymphocytes or macrophages prior to cocultivation did not lead to generation of suppressor activity.