PURINOCEPTOR FUNCTION IN THE IMMUNE-SYSTEM

Immune cells express plasma membrane receptors for extracellular adeno sine and purine and pyrimidine nucleotides. Overwhelming evidence sugg ests that these receptors have a pivotal role in the modulation of sev eral immune cell responses, and may therefore be very important in the overall economy of the immune network. Adenosine can be either an act ivatory or an inhibitory mediator. Nucleotides have a more complex eff ect, depending not only on the P2 receptor subtype activated but also on doses applied and tile length of stimulation. Both metabotropic (C- protein-linked) and ionotropic (intrinsic ion channels) P2 receptors a re present in immune cells and their expression is modulated by inflam matory cytokines and differentiation agents. The physiological meaning of the P2 receptors is still obscure; however, converging evidence fr om different laboratories suggest that they may be involved in a wide variety of responses such proliferation, differentiation, cell death, and cytokine release. (C) 1997 Wiley-Liss, Inc.