IL-27 and TCR stimulation promote T cell expression of multiple inhibitory receptors

Inhibitory receptors (IR) are a diverse group of cell surface molecules that modulate T cell activation, but there are gaps in our knowledge of the cell extrinsic factors that regulate their expression. The present study found that in vivo overexpression of IL-27 led to increased T cell expression of PD-L1, LAG-3, TIGIT, and TIM-3. In vitro, TCR stimulation alone promoted expression of multiple IRs, while IL-27 alone induced expression of PD-L1. However, the combination of intermediate TCR stimulation and IL-27 resulted in synergistic induction of LAG-3, CTLA-4, and TIGIT. In vivo, infection with Toxoplasma gondii resulted in parasitespecific effector T cells that expressed high levels of IR and at local sites of infection where IL-27 production was highest, IL-27 was required for maximal effector cell expression of PD-L1, LAG-3, CTLA-4 and TIGIT. Together, these results affirm the critical role of TCR signals in the induction of IR expression, but find that during infection, IL-27 provides a signal that promotes T cell expression of inhibitory receptors. Six-week-old female Balb/c mice were injected with 20 μg of either empty vector or linked human IL-27 minicircle DNA (System Biosciences, Palo Alto, CA) in 2 ml 0.9% normal saline via the tail vein over the course of 5 seconds (3 replicates each). Spleens were collected from mice five days after minicircle injection. Total RNA was extracted from splenocytes after mechanical dissociation and ACK lysis, with the RNeasy® Mini Kit (Qiagen, Cat. No: 74104). Gene expression profiling on was performed on Affymetrix GeneChip™ Mouse Gene 2.0 ST Arrays (Applied Biosystems, Cat. No: 902118).