Hormone receptors on cloned T lymphocytes. Increased responsiveness to histamine, prostaglandins, and beta-adrenergic agents as a late stage event in T cell activation.

Abstract

Lymphocytes have surface receptors for a variety of hormones that play an important part in modulating the immune response. Most previous studies, however, have examined the effects of hormone agonists on heterogeneous bulk populations of cells, making it difficult to precisely identify the responding target cells. We have therefore studied a set of well characterized T cell clones for a series of adenylate cyclase-linked hormone receptors and examined changes in receptor expression that occur after cell activation. All clones tested had receptors for histamine, isoproterenol, and PGE1, but not for several other cAMP-active hormone agonists. The apparent receptor affinities and their specificities were characteristic of typical histamine H2, beta 2-adrenergic, and PGE receptors. The cAMP response to PG was higher and longer lasting than that to histamine or isoproterenol, both of which appear to undergo receptor desensitization. After activation of quiescent cells in IL-2-containing media, the cAMP response to all three ligands increased, peaking 4 to 5 days after stimulation, and then returned to basal levels as the cells ceased proliferating. Inasmuch as this effect did not require Ag, it appears that the coordinate regulation of responsiveness to these ligands is a direct result of lymphocyte activation. This increase in hormone receptor activity is functionally analogous to the up-regulation of receptors for other ligands that occurs after lymphocyte activation and further demonstrates the important immunoregulatory role played by the changing repertoire of surface receptors that is associated with activation.