[The number of TIGIT+CD8+ T cells increases but their cytokine secretion decreases in the lungs of Plasmodium yoelii infected mice].

Objective To investigate the effect of T cell immunoreceptor with Ig and ITIM domains (TIGIT) on the function of CD8⁺ T cells in the lungs of Plasmodium infected mice. Methods The lungs of the mice infected with Plasmodium yoelii were isolated, weighed and photographed after 12 days' infection. After dissolution, lung lymphocytes were isolated, counted and stained, and then the contents of CD8⁺ and TIGIT⁺CD8⁺ T cells were detected by flow cytometry. The expressions of L selectin (CD62L), CD69, programmed death 1 (PD-1), CD25, and C-X3-C motif chemokine receptor 1 (CX3CR1) on TIGIT⁺CD8⁺ T cells were detected by flow cytometry. After stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin, the ability of TIGIT⁺CD8⁺T cells to secrete interferon γ(IFN-γ), interleukin 21 (IL-21), IL-4, IL-17, and IL-10 was detected. Results The body mass of mice with Plasmodium infection was reduced. The lungs became darker, and the ratio of the lung mass to body mass was significantly increased. Compared with the normal mice, the percentages and absolute quantity of CD8⁺ and TIGIT⁺CD8⁺ T cells in the lungs of the infected mice were significantly increased. The percentage of TIGIT⁺CD8⁺ T cells expressing CD62L in the infected group was significantly lower, while the percentage of the CD69, PD-1, and CX3CR1 cells were significantly higher than that of TIGIT⁺CD8⁺ T cells from the normal mice. The percentages of TIGIT⁺CD8⁺ T cells secreting IL-21, IL-4, IL-17 and IL-10 cells in the infected group were significantly lower. Conclusion The lung lesions from mice with Plasmodium infection are obvious, the numbers of TIGIT⁺CD8⁺ T cells increase, and these cells express a variety of activation-related molecules, but the ability to secrete cytokines is reduced.