CD4(+)FOXP3(+) Regulatory T Cells Exhibit Impaired Ability to Suppress Effector T Cell Proliferation in Patients with Turner Syndrome

OBJECTIVE: We investigated whether the frequency, phenotype, and suppressive function of CD4(+)FOXP3(+) regulatory T cells (Tregs) are altered in young TS patients with the 45,X karyotype compared to age-matched controls. DESIGN AND METHODS: Peripheral blood mononuclear cells from young TS patients (n = 24, 17.4–35.9 years) and healthy controls (n = 16) were stained with various Treg markers to characterize their phenotypes. Based on the presence of thyroid autoimmunity, patients were categorized into TS (–) (n = 7) and TS (+) (n = 17). Tregs sorted for CD4(+)CD25(bright) were co-cultured with autologous CD4(+)CD25(−) target cells in the presence of anti-CD3 and -CD28 antibodies to assess their suppressive function. RESULTS: Despite a lower frequency of CD4(+) T cells in the TS (-) and TS (+) patients (mean 30.8% and 31.7%, vs. 41.2%; P = 0.003 and P < 0.001, respectively), both groups exhibited a higher frequency of FOXP3(+) Tregs among CD4(+) T cells compared with controls (means 1.99% and 2.05%, vs. 1.33%; P = 0.029 and P = 0.004, respectively). There were no differences in the expression of CTLA-4 and the frequency of Tregs expressing CXCR3(+), and CCR4(+)CCR6(+) among the three groups. However, the ability of Tregs to suppress the in vitro proliferation of autologous CD4(+)CD25(−) T cells was significantly impaired in the TS (–) and TS (+) patients compared to controls (P = 0.003 and P = 0.041). Meanwhile, both the TS (–) and TS (+) groups had lower frequencies of naïve cells (P = 0.001 for both) but higher frequencies of effector memory cells (P = 0.004 and P = 0.002) than did the healthy control group. CONCLUSIONS: The Tregs of the TS patients could not efficiently suppress the proliferation of autologous effector T cells, despite their increased frequency in peripheral CD4(+) T cells.