Selectins and IL-6 during the clinical course of idiopathic thrombocytopenic purpura

'Stress thrombocytes', i.e, large and presumably hyperfunctioning platelets , is a well-known characteristic of patients with idiopathic thrombocytopen ic purpura (ITP). Therefore, despite what may be severe thrombocytopenia th ese patients generally do not suffer from severe life-threatening hemorrhag e. The plasma level of soluble P-selectin (sP-selectin) is a valuable marke r reflecting platelet activation. Available data suggest that interleukin-6 (IL-6) may contribute to the regulation of megakaryocytopoiesis and platel et activity. The purpose of this study is to investigate the status and kin etics of IL-6 and selectins, which are involved in the platelet function, p roduction, and immunologic functions, during the clinical course of ITP, th at may be helpful for understanding the biology of the disease. Twenty-two ITP patients were studied prospectively in the course of their disease. Six teen, 8 and 6 patients were available after platelet recovery, relapse and splenectomy, respectively. Fifteen healthy persons served as a control grou p. Higher levels of both sP-selectin and IL-6 were observed in all clinical stages of disease compared to the control group. However, more prominent e levations were present during active stages of ITP, i.e. pretreatment (p < 0.001 vs. control group for both sP-selectin and IL-6) and relapse periods (p < 0.001 vs. control group for both sP-selectin and IL-6). Pretreatment s oluble L-selectin and soluble E-selectin levels were not different from the controls. Both sP-selectin (r = -0.32, p = 0.019) and IL-6 (r = -0.41, p = 0.002) levels:inversely correlated with platelet count during disease cour se. There was a positive correlation between the sL-selectin level and leuk ocyte count,(r= 0.60, p < 0.001). These results suggest that residual plate lets are activated in ITP, which offers a relatively benign clinical course compared to other thrombocytopenias. High IL-6 concentration during thromb ocytopenia may be involved in compensatory megakaryocytopoiesis and augment ed 'residual platelet' functions in ITP.