OBJECTIVETo investigate the changes and roles of follicular regulatory T cells (Tfr) and follicular T helper cells (Tfh) in the pathogenesis of children immune thrombocytopenia (ITP).

METHODS32 untreated ITP patients, as well as 20 healthy controls were enrolled in this study. The proportion of circulating Tfr and Tfh cells were determined by flow cytometry; real-time PCR was performed to detect the expression of transcription factors and regulatory factors of Bcl-6, c-Maf, Blimp-1 and PD-1 mRNA; ELISA was used to detect plasma concentration of IL-2, IL-6, IL-10 and IL-21.

RESULTS(1)The proportion of Tfh cells were significantly higher (P<0.05), while the Tfr cells and the ratio of tfr/Tfh cells in ITP patients were significantly lower than that in health controls (P<0.05); (2)Correlation analysis showed that the Tfr cells and the ratio of Tfr/Tfh were positively correlated with the platelet counts and negatively with the levels of PA-IgG, while the proportion of Tfh cells was positively correlated with the levels of PA-IgG and negatively with the platelet counts in peripheral blood; (3)Transcription levels of Bcl-6 and c-Maf mRNA in CD4(+) T lymphocytes cells were significantly elevated, the Blimp-1 mRNA in CD4(+) cells and PD-1 mRNA levels of Treg were lower in ITP patients in comparison with healthy controls; (4)The higher Plasma concentration of IL-21, and lower concentration of IL-2 were found in ITP patients.

CONCLUSION(1)The lower proportion of Tfr cells and higher proportion of Tfh cells, as well as the abnormal ratio of Tfr/Tfh might account for the decreased platelet counts to be further involved in the immunological pathogenesis of children ITP; (2)The changes of plasma cytokines IL-2, IL-21 in microenvironment and the over-expression of Bcl-6 mRNA, c-Maf mRNA and the lower-expression of Blimp-1 mRNA in CD4(+) T cells, and over-expression of PD-1 mRNA in Treg cells might be account for the abnormal ratios of Tfr/Tfh cells in ITP patients.