FUNCTIONAL CHARACTERISTICS OF MONOCYTES II. FURTHER OBSERVATIONS ON LYMPHOCYTE-MONOCYTE COLLABORATION IN THE RESPONSE TO PHYTOMITOGENS

Abstract

Monocytes [human] play a crucial role in the response of lymphocytes to phytomitogens. This role is evident during the very early events after exposure to the mitogen. Significant lymphocyte transformation occurs when monocytes are removed from the culture within a few h after exposure to mitogen, and the presence of monocytes after the initial period is no longer necessary. Monocytes may be required for the early increase in protein synthesis and burst in RNA synthesis following exposure to the mitogen. Monocytes may help in lymphocyte responses partly by longer range, by way of release of soluble humoral factors into culture supernatant fluids. Temperature dependence of the effect of pulse exposure of lymphocytes to these supernatants raises the possibility that membrane receptors on these cells to humoral factors released by monocytes may exist. Monocytes do not appear to act primarily by preserving the viability of lymphocytes in culture.