IL-21 Is Increased in Peripheral Blood of Emphysema Mice and Promotes Th1/Tc1 Cell Generation In Vitro

Interleukin-21 (IL-21) has been reported to be involved in many Th1-associated diseases. However, the alteration and immune regulation of IL-21 in emphysema remains unknown. In this study, we tested the levels of IFN-γ and IL-21 and the frequencies of Th1 and Tc1 in peripheral blood from cigarette smoke (CS)-exposed mice and air-exposed mice and explored the effect of IL-21 on generation of Th1 and Tc1 cells in vitro. It was found that the levels of IFN-γ and IL-21 and the frequencies of Th1, Tc1, CD4⁺ IL-21⁺, CD4⁺ IL-21R⁺, and CD8⁺ IL-21R⁺ T cells were much higher in CS-exposed mice. Moreover, the levels of IL-21 were correlated positively with Th1 cells and with Tc1 cells. Finally, the in vitro experiments showed that IL-21 could promote Th1/Tc1 cell generation in CS-exposed mice. These results indirectly provide evidence that IL-21 produced by CD4⁺ T cells could promote Th1/Tc1 response, leading to systemic inflammation in emphysema.