ADENOSINE RECEPTORS ON HUMAN T LYMPHOCYTES AND HUMAN THYMOCYTES: 55

Abstract

Adenosine (ado) can effect the immune system via binding to cell-surface receptors on lymphoid cells, resulting in an increase in the intracellular level of cAMP. The basal amount of cAMP in T lymphocytes (range 1.6-9.0; mean 5.5 pmoles/107 cells) was significantly higher than that in thymocytes (range 0.2-1.7; mean 0.7 pmoles/107 cells). Incubation of thymocytes with 10 μM ado resulted in a rapid (1 min), transient increase in cAMP, whereas in T lymphocytes a prolonged (> 15 min) cAMP increase occurred. The effects of ado were most pronounced after incubation (15 min) with the non-metabolizable 2-chloro-ado and the phosphodiesterase inhibitor Ro20-1724. This resulted in a net increase in cAMP levels of 10-35 pmoles for thymocytes and 20-60 pmoles for T lymphocytes. Binding of ado to the ado receptor and the subsequent increase in the intracellular cAMP level may be a major event with respect to the effect of ado on T-lymphoid cells.