The role of macrophages in the production of lymphokines by T and B lymphocytes

The role of macrophages in the production of 2 lymphokines, monocyte chemotactic factor and macrophage activating factor, was investigated. Lymphokine production by guinea pig lymph node and spleen cells required macrophages for thymus dependent antigens and mitogens. In contrast, B cell stimulants which also induce the synthesis of lymphokines were macrophage independent. When populations of relatively pure B or T lymphocytes were isolated, it was found that T cells required viable macrophage cooperation to product these 2 lymphokines and to undergo proliferation in response to specific antigens, whereas B cells could be directly activated in the absence of macrophages. These findings suggest that T and B cells have different requirements for activation and for macrophage cooperation. Furthermore, since lymphokine synthesis is evident within the first 4 hr of stimulant presentation, these observations demonstrate that macrophages play an essential role in the earliest events of lymphocyte activation.