The PD-1/PD-L1 Pathway Affects the Expansion and Function of Cytotoxic CD8(+) T Cells During an Acute Retroviral Infection

David, Paul; Megger, Dominik A.; Kaiser, Tamara; Werner, Tanja; Liu, Jia; Chen, Lieping; Sitek, Barbara; Dittmer, Ulf; Zelinskyy, Gennadiy

The main function of virus-specific CTLs is the killing of cells expressing viral antigens. In order to analyze the cytotoxic potential of CTLs we performed an in vivo killing assay. In this assay the elimination of transferred donor spleen cells loaded with a viral epitope peptide and labeled with CFSE were analyzed. The cytotoxicity of CD8 + T cells was significantly higher at day 8 and at day 15 after infection in the spleen ( Figure 2E ) and bone marrow (Figure 2F ) of PD-1 −/− and PD-L1 −/− mice in comparison to WT mice. Interestingly, the efficacy of killing was always higher in PD-L1 KO mice than in PD-1 KO mice, reflecting the stronger expansion and effector cell activation in the PD-L1 deficient animals after FV infection.