Adenosine receptors on human inflammatory cells.

Adenosine is a natural nucleoside that plays a physiological role in the modulation of human inflammatory cells. We have investigated the presence of adenosine A2/Ra and A1/Ri receptors and of the P-site on human inflammatory cells. Human B and T(OKT4+ and OKT8+) lymphocytes, polymorphonuclear leucocytes, monocytes, basophils and platelets possess a membrane adenosine A2/Ra receptor. The activation of adenosine A2/Ra receptor increases the intracellular level of cyclic AMP in these cells. Human lymphocytes and neutrophils possess also an inhibitory adenosine A1/Ri receptor and a P-site whose activation inhibits the effect of many adenylate cyclase agonists including isoproterenol, PGE1, histamine, adenosine, cholera toxin and forskolin.