ENHANCING EFFECTS OF IL-2 ON M-CSF PRODUCTION BY HUMAN PERIPHERAL-BLOOD MONOCYTES

Monocytes have the capacity to produce granulopoietic factors such as M-CSF and G-CSF. Our findings here showed that interleukin-2 (IL-2), a t a concentration of more than 0.05 ng/ml, led to a 12-fold increase i n the production of M-CSF in the human peripheral blood mononuclear ce lls after 72 h incubation compared to the control culture. Even in pur ified monocyte cultures-with added IL-2, a 3-fold increase in M-CSF pr oduction was observed at an IL-2 concentration of 50 ng/ml. The enhanc ing effect of IL-2 on M-CSF secretion was also observed when IL-2-stim ulated non phagocytic cell-conditioned medium was added to monocyte cu ltures. These results indicated that IL-2, both directly and indirectl y, activated monocytes to enhance the production of M-CSF. In addition , the expression of 14,-2 receptor (CD25) on monocytes was more enhanc ed in cultures containing IL-2 than in cultures without IL-2. On the o ther hand, IL-2 did not induce G-CSF production in purified monocytes. These in vitro results suggest that when IL-2 is used clinically, the various biological activities of M-CSF should also be taken into cons ideration.