EFFECTS OF NORMAL PLATELETS ON PROLIFERATION AND CONSTITUTIVE CYTOKINE SECRETION BY HUMAN ACUTE MYELOGENOUS LEUKEMIA BLASTS

The effects of soluble E-selectin, P-selectin and normal platelets on acute myelogenous leukaemia (AML) blasts were investigated in vitro. W e investigated effects on spontaneous and cytokine-dependent blast pro liferation, and constitutive blast secretion of different cytokines, T he presence of normal platelets during in vitro culture caused a dose- dependent increase in both spontaneous and cytokine-dependent AML blas t proliferation, Addition of platelets also increased constitutive bla st secretion of Interleukin 1 beta (IL1 beta), IL6, GM-CSF and TNF alp ha, whereas platelets had no effect on the release of IL1 receptor ant agonist, The effects of platelets on constitutive cytokine secretion w ere also detected when platelets and AML blasts were cultured in diffe rent chambers separated by a permeable membrane, and a further enhance ment was achieved when blasts and platelets were cultured together, So luble P-selectin had no effect on constitutive AML blast cytokine secr etion or the platelet-induced enhancement of the secretion, However, b oth soluble E- and P-selectin altered AML blast proliferation for a mi nority of patients. We conclude that normal platelets can modulate the function of human AML blasts in vitro.