INHIBITION OF ANTI-CD3 MONOCLONAL ANTIBODY-INDUCED T-CELL PROLIFERATION AND INTERLEUKIN-2 SECRETION BY PHYSIOLOGICAL COMBINATIONS OF DEXAMETHASONE AND PROSTAGLANDIN E(2)

1. The purpose of these studies was to characterize further previous observations from our laboratory indicating that physiologic concentrations of dexamethasone (DEX) and prostaglandin E(2) (PGE(2)) added together result in synergistic inhibition of the proliferative response of T cells stimulated via the T-cell receptor CD3 signaling complex (TCR/CD3). 2. Various physiologic concentrations of DEX and PGE(2) were added to T cells stimulated with immobilized anti-CD3 monoclonal antibody (mAb) and cultured at optimal and suboptimal cell densities. The results demonstrate that the proliferative response of anti-CD3 mAb-stimulated T cells cultured at a suboptimal cell density is more suppressed than that of T cells cultured at optimal concentrations. 3. The proliferative response of CD4(+) T cells to immobilized anti-CD3 mAb was also determined in the presence of PGE(2) and DEX. The data indicate that the CD4(+) subset of T cells is more sensitive to the synergistic antiproliferative effects of DEX and PGE(2) compared to whole T-cell populations. 4. Various concentrations of DEX and/or PGE(2) were added to T cells stimulated with anti-CD3 mAb and the secretion of interleukin-2 (IL-2) was determined. The results demonstrate that concentrations of DEX and PGE(2) which individually do not significantly suppress IL-2 synthesis act together to inhibit the synthesis of IL-2 synergistically. 5. The addition of an exogenous source of recombinant IL-2 (rIL-2) to T cells stimulated in the presence of DEX and PGE(2) completely reversed the synergistic antiproliferative effect of these two compounds. This reversal was even more pronounced with T cells cultured at a suboptimal cell density. Additionally, PGE(2) and DEX did not affect expression of the IL-2 receptor (IL-2R), as measured by upregulation of the alpha chain, on anti-CD3 mAb stimulated T cells. 6. Collectively these data indicate that physiologic concentrations of PGE(2) and DEX, which alone have no effect on anti-CD3 mAb-induced T-cell proliferation, act synergistically to inhibit T-cell proliferation as well as IL-2 synthesis.