Impaired CD4⁺CD25⁺ regulatory T cell activity in the peripheral blood of patients with autoimmune sensorineural hearing loss

CD4⁺CD25⁺ regulatory T cells exert an immune regulatory function and thus play an important role in the control of self-reactivity in the pathogenesis of autoimmune inflammatory conditions. The aim of the study presented here is to perform a quantitative and functional analyses of these cells in patients with autoimmune sensorineural hearing loss (ASNHL). T cell subsets (CD4⁺CD25⁺, CD4⁺CD25^high, CD4⁺, and CD8⁺) from the peripheral blood of 17 patients with ASNHL, 16 patients with noise induced hearing loss (NHL), and 100 normal controls were analyzed by flow cytometry. The CD4/CD8 ratio was also analyzed. In addition, the suppressive capability of CD4⁺CD25⁺ T cells was tested in vitro by measuring their ability to suppress the proliferation and IFN-γ secretion of CD4⁺CD25⁻ T cells. No significant difference was found in the T cell subsets of ASNHL patients compared to normal controls or NHL patients, except that the proportion of CD4⁺ T cells was elevated in ASNHL patients. However, we did observe defective regulatory function of CD4⁺CD25⁺T cells in patients with ASNHL. Our data supported the idea that CD4⁺CD25⁺ regulatory T cells played an immunosuppressive function in the periphery. The impaired suppressive activity of these cells may be an important factor in the pathogenesis of ASNHL.