Role of IL-21/IL-21R-mediated CD4 + T cells in Chlamydia muridarum respiratory infection / 中华微生物学和免疫学杂志

ABSTRACT

Objective:To investigate the role of IL-21/IL-21R-mediated CD4 + T cells in Chlamydia muridarum ( Cm) respiratory infection. Methods:C57BL/6 mice (WT mice) and IL-21R -/- mice were used to establish the models of Cm respiratory infection through intranasal inhalation of Cm. Flow cytometry was used to detect the proportion, number, activity and function of CD4 + T cells in lung and spleen tissues at 0, 3, 7 and 14 d after Cm respiratory tract infection. IFN-γ and IL-4 levels in spleen cell culture supernatants were detected by ELISA. Na?ve WT mice were transferred with CD4 + T cells in the spleen tissues of IL-21R -/- mice or WT mice on 7 d after infection and given Cm intranasally 2 h later. Then the mice were weighed daily and sacrificed on 14 d after infection. The bacterial load and pathological changes in lung were analyzed. Flow cytometry was performed to detect the proportions and numbers of neutrophils (CD45 + CD11b + Gr-1 high) and alveolar macrophages (CD45 + F4/80 + CD11c high)as well as the proportions of Th1 (IFN-γ + CD4 + ) and Th2 (IL-4 + CD4 + ) cells. ELISA was also performed to measure IFN-γ and IL-4 levels in spleen cell culture supernatants. Results:Compared with WT mice, IL-21R -/- mice showed elevated numbers and enhanced activation of CD4 + T cells, increased proportion of Th1 cells and decreased proportion of Th2 cells in spleen and lung tissues after Cm respiratory infection. Besides, IFN-γ levels increased, while IL-4 levels decreased in spleen cell culture supernatants of IL-21R -/- mice. After Cm infection, the na?ve WT transferred with CD4 + T cells from IL-21R -/- mice showed less body weight loss, reduced bacterial load and alleviated pathological changes in lung tissues, increased proportion of Th1 cells in lung tissue and higher IFN-γ level in spleen cell culture supernatants. Conclusions:IL-21/IL-21R-mediated CD4 + T cells could aggravate Cm respiratory infection by suppressing Th1 cell immune responses.