The role of monocytes in IL-3 enhancement of human T cell proliferation

Abstract
We have assessed the role of recomblnant human Interieukin 3 (rlL-3) In the activation and proliferation of peripheral blood lymphocytes (PBL) and their various subsets. rlL-3 significantly enhanced the CD2-responslveness of unfractlonated PBL. Proliferating cells were mainly T lymphocytes and most of them expressed CD4. This effect was absent following adherent cell depletion from PBL. rlL-3 also failed to directly activate purified lymphocytes, nor did it Increase T cell responsiveness to mltogens and/or IL-2. By contrast, rlL-3 Induced monocyte functions as enhancement of IL-1 production was observed following treatment of these cells by rlL-3. This effect was removed by antl IL-3 mAb addition to these cultures. In addition, antl IL-1 antibody partially inhibits IL-3-derlved responses. Together, these data strongly suggest that IL-3 stimulation of T lymphocytes is related mainly to its ability to enhance monocyte functions.

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