NFIL3 contributes to cytotoxic T lymphocyte-mediated killing

Abstract

Cytotoxic T cells (CTLs) are key effectors of the adaptive immune system that recognise and eliminate virally infected and cancerous cells. In naïve CD8+ T cells, T cell receptor (TCR) engagement drives a number of transcriptional, translational and proliferation changes over the course of hours and days leading to differentiation into CTLs. To gain a better insight into this mechanism, we compared the transcriptional profiles of naïve CD8+ T cells to those of activated CTLs. To find new regulators of CTL function, we performed a selective CRISPR screen on upregulated genes and identified NFIL3 as a potential regulator of cytotoxicity. Although NFIL3 has established roles in several immune cells including NK, Treg, DC and CD4+ T cells, its function in CD8+ CTLs, is less well understood. Using CRISPR/Cas9 editing, we found that removing NFIL3 in CTLs resulted in a marked decrease in cytotoxicity. We found that in CTLs lacking NFIL3 TCR-induced extracellular signal-induced kinase (ERK) phosphorylation, immune synapse formation and granule release were all intact while cytotoxicity was functionally impaired in vitro. Strikingly, NFIL3 controls the production of cytolytic proteins as well as effector cytokines. Thus, NFIL3 plays a cell intrinsic role in modulating cytolytic mechanisms in CTLs.