Transient deficiency of peripheral blood accessory cells in supporting T cell mitogenesis in patients suffering from chronic idiopathic thrombocytopenic purpura after intravenous gammaglobulin treatment

Summary Mitogenic response of blood lymphocytes to phytohemagglutinin (PHA) and to OKT 3 monoclonal antibodies was investigated in 7 patients suffering from chronic idiopathic thrombocytopenic purpura (ITP) before, during and after high-dose intravenous (i. v.) immunogammaglobulin (IgG) infusion. The platelet count rose above the pre-treatment values during infusion therapy in all patients but one. Five out of seven patients presented elevated platelet-associated IgG (PA-IgG) levels at the time of the first infusion; four of these showed an increase in platelet count and a transient reduction or normalization of PA-IgG after IgG infusion. Five out of seven patients showed an impairement of T lymphocyte mitogenic response to PHA and OKT 3 before therapy. All patients responded to IgG therapy with a transient deficiency of FcR mediated monocytes (Mo) in supporting T cell mitogenesis induced by both mitogens during and after IgG infusion. This reduced cooperative capability of Mo disappeared at various times after the end of therapy (range 3–12 days). The transient alteration of Mo function, possibly due to a modification in the surface number or in the affinity of Fc-receptors, can explain in part, the increase in platelet count during and after IgSRK infusion.This work was supported by grants of the CNR (Progetto Finalizzato: Ematologia; Progetto Finalizzato: Trapianto d'Organo)