THE IN VITRO DIFFERENTIATION OF MONONUCLEAR PHAGOCYTES II . THE INFLUENCE 0~' SERUM ON GRANULE FORMATION, HYI)ROLASE P~ODUCrION~ AND PINOCYTOSIS* BY ZANVIL A. COHN, M.D. AND BELINDA BENSON

Previous communications from this laboratory delineated the events associated with the in vitro cultivation of unstimulated mouse mononuclear phagocytes (1, 2). These processes included a progressive increase in lysosome-like cytoplasmic granules. In addition, it was shown that two inhibitors of protein synthesis blocked the formation of both granules and hydrolytic enzymes. These data as well as the autoradiographic evidence of newly formed protein in the granule region suggested that this was an active process associated with the formation of new hydrolytic enzymes. This report is an extension of these findings in which the origin, rate of formation, and controlling factors connected with granule and hydrolase production have been examined in more detail.