[The changes of circulating follicular regulatory T cells and follicular T helper cells in children immune thrombocytopenia].

OBJECTIVE: To 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).

METHODS: 32 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.