Studies on macrophage function in in vitro immune response Part 1. The role of macrophages in lymphocyte reaction to polyclonal B cell activator

To clarify the function of macrophages (MΦ) in lymphocyte reaction to polyclonal B cell activator (PBA), especially pokeweed mitogen (PWM) and Staphylococcal phage lysate (SPL), the pattern of PWM-induced IgG synthesis and the degree of PBA-induced DNA synthesis by unfractionated mononuclear cells (MNC) or MΦ depleted MNC fraction were examined. The response of the MΦ depleted MNC fraction to PBA was significantly higher than that of unfractionated MNC. The addition of 10% MΦ to the depleted MNC fraction enhanced both responses, but too many MΦ reduced PWM-induced IgG synthesis. These results suggest that the presence of MΦ is not necessary in PBA-induced lymphocyte reaction and that the maximal response is obtained by the addition on optimal number of MΦ. Moreover, an excessive number of MΦ suppresses the IgG synthetic response