EFFECT OF PGE(2) ON THE CELL-SURFACE MOLECULE EXPRESSION IN PMA TREATED THYMOCYTES

PGE(2) is produced by cells of the thymic microenvironment. The effect s of PGE(2) are mediated by cAMP through binding to its intracellular receptor protein kinase A (PKA). Phorbol 12-myristate 13-acetate (PMA) is known to modulate CD molecule expression on thymocytes, probably t hrough activation of protein kinase C (PKC). We have hypothesized that cross-talk between these two signalling pathways may affect modulatio n of the CD molecules on the cell surface of thymocytes. For this purp ose, we compare the effects of PMA alone or combined with PGE(2) on CD 3, CD4 and CD8 expression on mouse thymocytes by flow-cytometric analy sis. PMA treatment almost completely abolished CD4 expression and slig htly decreased CD3 and CD8 expression. PGE(2) alone did not change the CD3, CD4 and CD8 molecule expression. Combined with PMA, PGE(2) can o vercome the decrease induced by PMA of the CD3 expression and partiall y reduced the disappearance of the CD4 molecule. On the other hand PGE (2) accelerated the loss of CD8 molecule expression. These events occu rred only in CD4+ CD8+ immature thymocytes. An analogue of cAMP (dibut ryl cAMP) mimics the effect of PGE(2), but not Br-cGMP. This different ial regulation by PGE(2) of the CD molecule expression on immature thy mocytes may provide additional evidence on the role of PGE(2) during t he process of thymic differentiation. (C) 1998 Elsevier Science B.V. A ll rights reserved.