Mechanisms of Corticosteroid Action in Immune Thrombocytopenic Purpura ( ITP ) : Experimental Studies Using ITP - Prone Mice , ( NZW X BXSB )

To determine the mechanism by which platelet counts increase after corticosteroid therapy for human immune thrombocytopenic purpura (ITP), we studied the platelet kinetics using prednisolone (PDN)-treated ITP-prone mice, (NZW x BXSB) F, (W/B F,). An increase in platelet counts was observed in W/B F, mice (n = 10, mean f SD, 1,202 f 202 x 103/pL) 4 weeks after treatment with PDN (2 mg/ kg/d); no increase occurred in nontreated W/B F, mice (n = 5,651 f 126, P < .005). Prolonged platelet life-spans (PLSs) were observed in treated W/B F, mice (1.29 f 0.40 days), but not in nontreated controls (0.60 f 0.24 days, P < .Ol). No increase in platelet production (platelet turnover) was found in PDN-treated W/B F, mice, but significant decreases in platelet-associated antibodies (PAAs) and platelet-bindable serum antibodies (PBAs) were noted. Studies on organ