Evidence suggests that chronic idiopathic inflammation, present in mucosa of human conjunctiva bronchial tree, GU and GI tracts, is often T lymphocyte-mediated. Few substances are known that can substantially retard immune-mediated injury in human mucosa without associated broad-spectrum T and B cell suppression. The challenge is to identify a locally active substance that reversibly retards tissue injurious T lymphocyte responses, particularly the cytokine secretion by CD4+ T-cells in humans at affected sites in mucosa, and which leaves the remainder of the immune system intact. PGE2 has been well-known to down regulate T lymphocyte function, especially cytokine release. The recent discovery that a single receptor type (EP4) for this potent locally active down regulator of T lymphokine release is present on T lymphocytes in many mucosa-bearing organs suggests an innovative approach to inflammation affecting mucosal organs. The hypotheses to be tested in the proposed studies are: (1) activation of the EP4 receptor on the T cell plasma membrane is associated with reduced cytokine-induced tissue injury; and (2) the insertion of non-EP4 receptors into the T cell membrane, as well as the use of EP receptor-specific pharmacological agonists and antagonists that alter the intra-cellular level of cAMP, will enhance the PGE2-driven reduction in pro- inflammatory cytokine release and subsequent tissue injury. Success in this endeavor could open up several new areas for study. Approaches to be used to achieve this long-term objective are physiological (receptor density by radioligand binding; transmonolayer electrical potential difference); molecular (transfection of mucosal T lymphocytes with EP receptor genes; immunological (characterization with specific immunoglobulin, and cell separation, based on surface markers); pharmacological (receptor induction and 131 binding studies) and biochemical (quantitating cAMP and receptor number). Thus, through the use of human T lymphocytes from many sites with mucosa throughout the body, as well as a potent macromolecule which new data suggests reduces cytokine secretion by T lymphocytes, the proposed research may reveal ways in which cellular receptors on mucosal T cells could be targeted to spare injury to adjacent tissue.
