Intrinsic PD‐L1 promotes antitumor activity of CD8+ cytotoxic T lymphocytes via in cis interaction with CD80

Abstract

Abbreviations aAPC artificial antigen presenting cell ANOVA analysis of variance CCK8 cell Counting Kit-8 CTL cytotoxic T lymphocyte IL-2 interleukin-2 IFN-γ interferon-γ NFAT nuclear factor of activated T cells OVA257-264 ovalbumin peptide 257-264, SIINFEKL OKT3 membrane-associated anti-human CD3 PD-L1 programmed cell death ligand 1 PD-1 programmed death protein 1 qPCR quantitative RT-PCR scFv single-chain variable fragment shRNA short hairpin RNA TCR t cell receptor TNF-α tumor necrosis factor-α Dear Editor, Programmed cell death-ligand 1 (PD-L1) on tumor cells can inhibit CD8+ cytotoxic T lymphocyte (CTL)-mediated antitumor response by trans-engagement with programmed death protein 1 (PD-1). Besides tumor cells, PD-L1 is expressed on T cells. At 7 days post CTL transfer, the number of transferred control or PD-L1-overexpressing CD45.1+ OT-I CTLs in the tumor, spleen, and lymph node of recipient mice were assessed using flow cytometry (M), and the percentages of IFN-γ+ and TNF-α+ transferred CTLs in tumor were estimated by intracellular staining (N) (n = 4). Abbreviations: aAPC, artificial antigen presenting cell; ANOVA, analysis of variance; CTL, cytotoxic T lymphocyte; IFN-γ, interferon-γ; IL-2, interleukin-2; KO, knock out; mRNA, messenger RNA; NFAT, nuclear factor of activated T cells; OD, optical density; PD-L1, programmed cell death ligand 1; PD-1, programmed death protein 1; SEM, standard error of mean; sgRNA, small guide RNA; shRNA, short hairpin RNA; TIL, tumor infiltrating lymphocyte; TCR, T cell receptor; TNF-α, tumor necrosis factor-α. PD-L1 knockout greatly downregulated the NFAT activity in Jurkat-NFAT-Luc cells upon aAPC stimulation (Figure 1D) and notably decreased IL-2, IFN-γ, and TNF-α mRNA levels in Jurkat-NFAT-Luc cells stimulated with anti-CD3 and anti-CD28 antibodies (Figure 1E).