It is now generally recognized that the anti-inflammatory and immunosuppressive actions of glucocorticoids play a physiological role in homeostatic regulation of immunity. Another homeostatic mechanism that becomes operant during the immune response is the production of PGE2 by macrophages. As with glucocorticoids, the immunomodulatory effects of PGE2 are evidenced by inhibition of T-cell proliferation and cytokine production. Thus, under circumstances where elevated levels of these substances occur concomitantly (i.e. stress and/or inflammatory responses), increased concentrations of glucocorticoids and PGE2 in an inflammatory site will contribute to the inhibition of T-cell function. This is supported by recent evidence from the investigators, which indicates that physiologic concentrations of PGE2 and dexamethasone synergistically inhibit anti- CD3 monoclonal antibody induced T- cell proliferation and IL-2 production when compared to the individual effects of these agents. The hypothesis to be tested, is that PGE2 and dexamethasone (a synthetic glucocorticoid) mediate their synergistic immunosuppressive effect via distinct signalling pathways which converge at the level of regulation of IL-2 synthesis. The experiments proposed are designed to investigate interactions of these distinct signalling pathways at cellular and molecular levels. More specifically, the experiments will examine PGE2 effects on early signalling events induced by the TCR such as on protein kinase activities, activation of phosphoinositol pathway or the serine/threonine phosphatase, calcineurin.
The second aim i s to examine nuclear events which regulate IL-2 gene transcription. These include the kinetics of appearance, magnitude, and stability of IL-2 mRNA plus the induction or activation of specific IL-2 transcription factors.
