Treatment of adult patients with idiopathic thrombocytopenic purpura with intravenous immunoglobulin: effects on circulating T cell subsets and PWM-induced antibody synthesis in vitro.

Eight adult patients with idiopathic thrombocytopenic purpura (ITP) were given two 5-d courses of intermediate (250 mg/kg body weight/d) to high dose (400 mg/kg body weight/d) intravenous infusions of human plasmin-cleaved Ig, at 15-30 d intervals. Three patients also were given single booster infusions (400 mg/kg body weight for 1 d) of a different preparation, S-sulfonated Ig. As expected, significant though transient rises in the platelet count were consistently observed in all patients. The mean platelet count increase was 95 600/mm3 after the first course, and 143 500/mm3 after the second course. Similar effects of lower magnitude were obtained several times in the patients given single booster doses. In three patients, platelet-bound IgG levels were decreased in association with Ig therapy. Phenotypic analysis of T cell subsets before starting Ig therapy and at the end of the second high dose course of intravenous Ig treatment revealed significant reductions in the proportion of T4+ lymphocytes in five patients and relative increases in the percentage of T8+ cells after therapy. As the overall proportion of T3+ cells remained unchanged, the T4+/T8+ ratio was therefore decreased. The total number of circulating lymphocytes was also decreased following therapy. In addition, PWM-driven Ig biosynthesis in vitro was significantly impaired after therapy in most patients, the capacity to synthesize IgG being mainly affected. It is concluded that, in addition to the reported transient blockade of the reticuloendothelial system, non-specific suppression of polyclonal Ig biosynthesis induced by the high dose Ig infusions also contributes to the net increase in platelet count.