To test if ATRA intrinsically regulates Th2 cell prolifera tion, we employed in vitro differentiated human Th2 cells and examined their proliferation after modulation HTS with RAR agonist and antagonist treatment. As expected, T cell receptor plus IL 2 stimulation induced many more generations of cell division than did IL 2 alone. In the presence of IL 2 alone ATRA significantly increased Th2 cell proliferation. With maximal activation, ATRA did not further augment Th2 cell proliferation. We next examined whether RAR modulation diffe rentially affected the proliferation of human Th2 sub populations. Among in vitro differentiated Th2 cells, ATRA augmented IL 2 induced proliferation of both the IL 5 and IL 5 subpopulations. Inhibitors,Modulators,Libraries However, Ro41 significantly inhibited the proliferation of the IL 5.

but not the IL 5 subpopulation. This Ro41 inhibition further demonstrates the differential re sponsiveness of the IL 5 vs. IL 5 Th2 subpopulations to RAR modulators. To further address the cellular mechanisms responsible for the ATRA mediated increase in IL 5 Th2 cell output, we examined ATRA induction of apoptosis. Notably, ATRA did not alter annexin Inhibitors,Modulators,Libraries V expression by CD4 T cells in Th2 dominant HDM proliferation cultures. Additionally, ATRA did not affect caspase 3 activation in CD3 activated Th1 or Th2 cell lines. Inhibitors,Modulators,Libraries In sum, these data demonstrate that ATRA positively regulates Th2 cell proliferation via T cell intrinsic me chanisms, and that RAR modulators have specificity for the IL 5 Th2 subpopulation. Additionally, apoptosis is not Inhibitors,Modulators,Libraries playing a major role in the preferential outgrowth of IL 5 Th2 cells induced by ATRA.

ATRA inhibits in vitro Th2 cell differentiation Inhibitors,Modulators,Libraries We next examined whether the pro Th2 effects of ATRA may be due to augmentation of Th2 differen tiation. We hypothesized that the addition of ATRA to in vitro Th2 cell differentiation cultures would enhance the frequency and or kinetics of appearance of Th2 cytokines. Counter to our hypothesis, ATRA inhibited Th2 cell differentiation selleck chemical Perifosine of both 2 Th2 and 3 Th2 cells. ATRA and Ro41 reciprocally regulate IL5, but not IL4 or IL13, gene expression We next tested the hypothesis that RAR modulators directly regulate Th2 cytokine gene expression via Th2 cell intrinsic mechanisms. IL 2 activation increased expression of IL5 message, which was significantly modulated by ATRA and Ro41, in a re ciprocal manner. No differences were observed in IL4 or IL13 gene expression. These data demonstrate that in addition to their effects on IL 5 Th2 cell proli feration, RAR modulators directly regulate IL5 gene expression. Discussion Here we report that the pro Th2 effect induced by reti noic acid is primarily a direct result of Th2 cell intrinsic regulation of the cytokine IL 5 by RAR.