Increased proliferation rate of lymphoid cells transfected with the P2X(7)ATP receptor

Human leukocytes can express the P2X(7) purinergic receptor, an ionic chann el gated by extracellular ATP, for which the physiological role is only par tially understood. Transfection of P2X(7) cDNA into lymphoid cells that lac k this receptor sustains their proliferation in serum-free medium. Increase d proliferation of serum-starved P2X(7) transfectants is abolished by the P 2X(7) receptor blocker oxidized ATP or by the ATP hydrolase apyrase. Both w ild type and P2X(7)-transfected lymphoid cells release large amounts of ATP into the culture medium. These data suggest the operation of an ATP-based autocrine/paracrine loop that supports lymphoid cell growth in the absence of serum-derived growth factors.