Functional platelet-activating factor receptors in immature forms of leukemic blasts.

Platelet-activating factor (PAF) is a phospholipid mediator with potent immunoregulatory activities on mature leukocytes. PAF modulates leukocyte cytosolic Ca2+ concentration ([Ca2+]i) through a Gq mediated pathway. We highlight, for the first time, Gq transcripts, PAF receptor (PAF-R) transcripts and protein in blast cells of acute myeloid (AML) and lymphoid (ALL) leukemia patients. PAF stimulated [Ca2+]i in leukemic blast cells; PAF effects being prevented by a specific PAF-R antagonist. In conclusion, functional PAF-R are present in blast cells of patients with acute leukemia; a result that could be of physiologic importance regarding the important effect of PAF on leukocytes maturation and functions.