We recently showed that the physiological compound ATP simultaneously inhibited TNF-alpha and stimulated IL-10 release in LPS-PHA stimulated blood. The purpose of the present study was to determine the mechanism involved in the concerted modulatory effect of ATP on TNF-alpha and IL-10. Incubation of blood with ATP in the presence of selective P2 receptor antagonists showed that the stimulatory effect of ATP on IL-10 release was completely annihilated by both 2-MeSAMP (a P2Y(12/13) receptor antagonist) and PSB-0413 (a P2Y(12) receptor antagonist). On the other hand, the inhibitory effect of ATP on TNF-alpha release was completely reversed by 5'-AMPS (a P2Y(11) receptor antagonist) as well as by H-89, an inhibitor of cAMP-activated PKA. The concerted inhibition by ATP of TNF-alpha release via P2Y(11) activation and stimulation of IL-10 release via P2Y12 activation implicates a novel approach towards immunomodulation by altering the balance among pro-and anti-inflammatory cytokines. (c) 2006 Elsevier Inc. All rights reserved.