[Role and mechanism of CD161 + regulatory T cells in alleviating cardiac valve injury in rheumatic heart disease rats].

Objective To investigate the role of CD161 ⁺ regulatory T cells (Treg) in reducing valve injury in rheumatic heart disease rats and the underlying mechanism. Methods CD161 ^- and CD161 ⁺ regulatory T cells (Tregs) were separated by flow cytometry and then cultured. The concentrations of interleukin 10 (IL-10) and transforming growth factor β (TGF-β) in the supernates were detected by ELISA. Rat models of rheumatic heart disease were established by mixing A type hemolytic streptococcus suspension with Freund's complete adjuvant. They were divided into control group, CD161 ^- Treg group and CD161 ⁺ Treg group. One week later, heart blood and mitral valve were taken from the model rats. The proportion of follicular helper T (Tfh) cells, B cells and plasma cells was detected by flow cytometry. Histopathological changes were detected by HE staining and the number of B cells and plasma cells by immunohistochemical staining. ELISA was used to detect the level of IL-21 in serum. Results The ability of CD161 ⁺ Tregs to secrete IL-10 and TGF-β was significantly higher than that of CD161 ^- Tregs. Compared with the rats injected with CD161 ^- Tregs, CD161 ⁺ Tregs could significantly reduce the damage of valve tissue and the proportion of B cells and plasma cells in valve tissue. Moreover, CD161 ⁺ Tregs injection could reduce the proportion of Tfh cells, B cells and plasma cells in rat blood and decrease the content of IL-21 in serum. Conclusion CD161 ⁺ Tregs can reduce the valve injury of rheumatic heart disease by inhibiting the proliferation and differentiation of Tfh cells and B cells.