DIFFERENTIAL PRODUCTION OF INTERLEUKIN-3 IN HUMAN T-LYMPHOCYTES FOLLOWING EITHER CD3 OR CD2 RECEPTOR ACTIVATION

Interleukin-3 (IL-3) is expressed in T lymphocytes and stimulates the growth of multipotent hematopoietic progenitors. Little is known, howe ver, about the stimuli that lead to IL-3 protein release. We examined IL-3 and granulocyte-macrophage colony-stimulating factor (GM-CSP) mRN A expression and protein secretion in human T lymphocytes following ac tivation via the TCR/CD3 complex, the CD2 receptor, and the IL-2 recep tor. GM-CSF mRNA expression and protein release were found in CD3- and CD2-activated T cells with maximum GM-CSF release following stimulati on with IL-2. IL-3 protein release is regulated via the CD2-receptor w ith virtually no IL-3 release after T cell stimulation via CD3. In con trast, IL-3 mRNA accumulation is more pronounced after CD3 activation than after CD2 activation. This suggests that upregulation of IL-3 pro tein release following T cell stimulation via CD2 occurs largely at th e translational or posttranslational level. These data also indicate t hat differential control of cytokine production can occur in response to activation of the alternative T cell receptor. interaction of the T cell CD2-receptor with its natural ligand LFA-3 expressed on stromal cells might represent a regulatory mechanism for rapid release of IL-3 , facilitating proliferation of multipotent hematopoietic cells.