Alteration of Circulating Regulatory T Cells in Japanese Adult Patients with Immune Thrombocytopenic Purpura after Eradication of Helicobacter Pylori.

Immune thrombocytopenic purpura (ITP) is an autoimmune disorder, and eradication of Helicobacter pylori (HP) has been demonstrated to be an effective and tolerable firstline treatment for the patients infected with HP in Japan. However the mechanism has still remained to be uncovered. Recently CD4+CD25high+Foxp3+ regulatory T cells (Tregs), which regulate autoreactive T cells, have been identified, and suggested to play an important role in pathogenesis of ITP, as well as other autoimmune disorders. It has been shown that Tregs are reduced and suppressed in the ITP patients. And a recent report has demonstrated that the defective Tregs are restored upon the rituximab treatment. However, the effects of HP eradication therapy on Tregs have not been determined. The aim of this study is to investigate the circulating Tregs in ITP patients treated with HP eradication. And we also attempted to elucidate the mechanisms of the treatment. The peripheral blood CD4+CD25high+ Tregs were measured by flow cytometry before and after the treatment in 21 Japanese adults with HP-positive chronic ITP. We also confirmed the expression of Foxp3 in this cellular population with the permeabilized mononuclear cells. Among 21 patients, the platelet counts increased in 13 cases (responders), but not in 9 cases (non-responders). In responders the numbers of Tregs have been restored, but not in non-responders after the treatment. It is interesting here that the amounts of Tregs were still transiently elevated in an early phase (2–3weeks) after the treatment in some non-responders without recovery of the platelet counts. Furthermore, in three cases, who failed in pylorus elimination, Tregs were also transiently increased in number associated with brief recovery of the platelet counts, and reduced to the initial level in about two months. After the successful re-eradication, the numbers of Tregs and platelets have been restored. From these results it is shown that HP eradication can modulate Tregs to increase the platelet counts for ITP patients. We also demonstrate that the increase of Tregs by HP eradication was more rapid than that by rituximab, which required about three months. Further, it might be suggested that there are two phases of the therapy with HP eradication for ITP. In an initial stage, the therapy itself could have an effect modulating the immune systems to potentiate Tregs. Some drugs, such as macrolide antibiotics including clarithromycin have been demonstrated to be a potent immunomodulator. However, this phase is not sufficient for the successful treatment, as shown in the cases of failure in HP elimination. In a retentive stage, extermination of HP is also necessary for sustainment of restored Tregs.