MEGAKARYOCYTE-RELATED INTERLEUKINS IN REACTIVE THROMBOCYTOSIS VERSUS AUTONOMOUS THROMBOCYTHEMIA

The primary thrombocytosis (thrombocythemia) associated with myeloprol iferative disorders is believed to be due to autonomous platelet produ ction. Secondary or reactive thrombocytosis can be observed in a numbe r of clinical circumstances, and may be related to persistent overprod uction of some thrombocytopoietic factors acting on megakaryocytes. Se veral cytokines, including IL-6, IL-1 and IL-4 have been shown to act alone or in concert, to affect various cellular stages of megakaryocyt opoiesis in humans. The aim of this study is to assess the serum conce ntrations of these cytokines in myeloproliferative disorders (MPD) wit h thrombocythemia and in rheumatoid arthritis (RA) with marked reactiv e thrombocytosis. Twenty-two patients (14 men, 8 women) with MPD and t hrombocythemia (platelet counts >500 x 10(9)/l; range 507-996 x 10(9)/ l), 33 RA patients (28 women, 5 men) with marked thrombocytosis (plate let counts >500 x 10(9)/l; range 500-745 x 10(9)/l), 27 RA patients (2 4 women, 3 men) with normal platelet counts (range 168-399 x 10(9)/l) and 15 healthy volunteers (8 women, 7 men) with normal platelet counts (range 161-385 x 10(9)/l) enrolled in the study. Serum IL-1 alpha, IL -1 beta, IL-4 and IL-6 concentrations were measured in these four grou ps. Of the 22 patients with MPD, 10 had chronic myelogenous leukemia, 5 had polycythemia vera, 6 had essential thrombocytosis and 1 had oste omyelofibrosis. Serum interleukin concentrations in patients with MPD and thrombocythemia were either suppressed or similar to those of norm al subjects, whereas IL-6, IL-1 beta and IL-4 levels were increased in RA patients with reactive thrombocytosis. We conclude that thrombocyt hemia associated with MPD is an autonomous phenomenon, and is not regu lated by cytokines which affect megakaryocytopoiesis.