WNT5A transforms intestinal CD8αα+ IELs into an unconventional phenotype with pro-inflammatory features

Background: Intestinal intraepithelial lymphocytes that reside within the epithelium of the intestine form one of the main branches of the immune system. A majority of IELs express CD8a homodimer together with other molecules associated with immune regulation. Growing evidence points to the WNT signaling pathway as a pivotal piece in the immune balance and focuses on its direct regulation in intestinal epithelium. Therefore we decided to investigate its role in IELs' immune status determination. Method: DSS colitis was induced in male C57BL mice. IELs were isolated from colon samples using mechanical dissociation followed by percoll gradient purification and Magnetic-activated cell sorting. Phenotype and cytokine production and condition with Wnts were analyzed by flow cytometry, real-time PCR or ELISA. Proliferation of lymphocytes were evaluated using CFSE dilution. Cell responses after WNT pathway interference were also evaluated. Results: Non-canonical WNT pathway elements represented by FZD5, WNT5A and NFATc1 were remarkably elevated in colitis IELs. The non-canonical WNT5A skewed them into a pro-inflammatory category as measured by inhibitory cell surface marker LAG3, LY49E, NKG2A and activated marker CD69 and FASL. Gaining of a pro-inflammatory marker was correlated with increased IFN-gamma production but not TNF whilst decreased TGF-beta and IL-10. Both interrupting WNT5A/PKC pathway and adding canonical WNT stimulants could curtail its immune-activating effect. Conclusion: Canonical and non-canonical WNT signals act in opposing manners concerning determining CD8 alpha alpha(+) IELs immune status. Targeting non-canonical WNT pathway may be promising in tackling inflammatory bowel disease.