Alteration of T cell subsets and immunoglobulin synthesis in vitro during high dose γ--globulin therapy in patients with idiopathic thrombocytopenic purpura.

T cell subsets of peripheral lymphocytes were studied using monoclonal antibodies (OKT3. OKT4, OKT8) and immunoglobulin (IgG, IgM, IgA) synthesis in vitro by peripheral mononuclear cells stimulated with pokeweed mitogen was studied in adult patients with idiopathic thrombocytopenic purpura before and after high-dose intra-venous intact gamma(γ-)globulin therapy, at a daily dose of 0.4g/kg body weight for 5 consecutive days. A transient increase in platelet count which reached a peak on the 1st to 2nd day after the end of the therapy was observed in four of five patients. Immunoglobulin synthesis in vitro was suppressed remarkably following therapy in all cases: the mean reduction of IgG, IgM and IgA was 78, 66 and 48% respectively. Titres of various autoantibodies, TGHA, MCHA, ANF and anti-DNA antibody, also decreased following therapy. In correspondence to this, phenotypic analysis in T cell subsets showed a decrease of OKT4+ : OKT8+ ratio following therapy, without a change in the proportion of OKT3+ cells. These data indicate that the intravenous γ-globulin preparations suppressed synthesis of antibodies non-specificially and caused a relative increase of OKT8+ suppressor T cells. [ABSTRACT FROM AUTHOR]