Expansion of the intraepithelial lymphocyte (IEL) compartment results in an increased bioenergetic profile and reduced IFNγ production in γδ IELs.

Abstract

Abstract Intestinal γδ intraepithelial lymphocytes (γδ IEL) serve as the first line of defense against pathogen invasion. We recently identified a transmissible hyperproliferative γδ IEL (γδ HYP) phenotype that protects against enteric infection, and these mice have no signs of overt intestinal pathology. Given that IELs are metabolically constrained to prevent aberrant activation, we hypothesized that the bioenergetics of γδ HYPIELs may regulate their effector function. Electron microscopy revealed a 70% increase in mitochondrial number (p=0.005) and 24% increase in mitochondrial area (p=0.04) in γδ HYPIELs relative to WT. Seahorse mitochondrial stress assays on γδ IELs showed a 50% increase in spare respiratory capacity in γδ HYPIELs compared to WT (p=0.014). Mitochondrial metabolism was shown to influence γδ T cell cytokine production, and similarly, we found that stimulation with PMA and ionomycin reduced the frequency of IFNγ +γδ IELs by 59% in γδ HYPrelative to WT (p<0.0001). We also observed that γδ HYPIELs exhibit higher CD39 expression compared to WT (p<0.0001), and a CD39 hisubset produces less IFNγ compared to CD39 negand CD39 intcells (p<0.0001) The addition of the ATP-synthase inhibitor oligomycin during IEL stimulation increased IFNγ production by both WT and γδ HYPIELs by 66% and 44%, respectively (p<0.0001). Together, our data demonstrate that the shift towards high CD39 expression and elevated mitochondrial metabolism contribute to decreased IFNγ production in γδ HYPIELs. Further understanding of the mechanisms regulating γδ IEL homeostasis and effector function may ultimately allow fine tuning of mucosal surveillance to confer protection against intestinal injury or infection while limiting aberrant cytotoxicity. Supported by NJCCR (COCR23PRF024)