Macrophage-dependent and B-cell-dependent proliferative T-cell populations in the peritoneal exudate cells of immunized mice.

: The antigen-dependent proliferative response of the Ia- T lymphocyte population in peritoneal exudate cells (PEC) of C3H/HeN mice immunized with horse red blood cells (HRBC) was examined by determining the uptake of tritiated thymidine ([3H]TdR) into the cells in vitro. Both the antigen and accessory cell population, which was either macrophages or B lymphocytes that had been prepared from the PEC or spleen of unimmunized mice, were necessary for the proliferative response of the Ia- T cell population and also the production of IL-2 by the Ia- T cells, but the Ia- T cell population could proliferate in the absence of antigen and accessory cells, if IL-2 was present. The IL-2-dependent proliferation of the Ia- T cells was augmented in the presence of macrophages, but not B cells. The Ia- T cells that had been treated previously with anti-IL-2 receptor (IL-2R) antibody showed no response to IL-2 in the presence or absence of B cells, but responded to IL-2 in the presence of macrophages. Direct contact of the Ia- T cells with macrophages seemed to be necessary for augmentation of the proliferative response of the Ia- T cells to IL-2 because the separation of these cell populations by a membrane filter in a Marbrook type culture vessel resulted in poor augmentation of the response. Cell-associated IL-1 did not participate in the augmentation because paraformaldehyde-treated macrophages did not help the response. When the Ia- T cells had been previously treated with complement and anti-asialo GM1 antibody, the IL-2-dependent proliferative response was not affected, but the augmentation of the response by macrophages was blocked. Previous treatment of the cells with anti-L3T4 antibody diminished the response to IL-2, but did not affect the augmentation of the response by macrophages. Pretreatment of the cells with anti-Thy-1.2-antibody reduced the response to IL-2 and the augmentation by macrophages. Therefore, we concluded that there are at least two populations, capable of responding to IL-2 in the immune Ia- T cell population; one with L3T4 surface antigen and another with asialo GM1 antigen. The response of the latter cells, but not the former, to IL-2 is augmented in the presence of macrophages.