Intravenous high-dose IgG therapy induced alterations of spleen lymphocyte IgM secretion and T cell subsets in patients with idiopathic thrombocytopenic purpura.

High-dose intravenous (IV) IgG therapy is an effective possible means of raising platelet counts in patients with idiopathic thrombocytopenic purpura (ITP). In order to elucidate further the mechanism of action of such treatment we comparatively studied spleen mononuclear cells (SMC) from two groups of ITP patients. Group I consisted of 9 patients who had not received any recent treatment before splenectomy. The 8 patients in group II had received IV IgG infusions 1-5 days before splenectomy. The SMC were cultured either unstimulated or stimulated by pokeweed-mitogen (PWM), and proliferation (as assessed by 3H-thymidine uptake), and IgG and IgM secretion were measured. In addition T lymphocyte subsets were determined in the SMC by indirect immunofluorescence using monoclonal antibodies (OKT3,4,8). By comparison with group I SMC, our results in group II SMC mainly showed a significant decrease in proliferation and IgM secretion, in both unstimulated and PWM stimulated cultures. In addition, a significant decrease in the proportion of T helper-inducer lymphocytes (OKT4+ cells) was also found in group II SMC, as compared to group I SMC. However, these immunological alterations in group II SMC were paradoxically more pronounced in those patients who failed to respond to IV IgG infusions. Thus, these results suggest that, although immune suppression takes place in the SMC of ITP patients following IV IgG therapy, it has not a pronounced effect on the increase of platelet.