Transmembrane protein CMTM6 inhibits Th17 cell differentiation and autoimmune inflammation in experimental dry eye

Abstract

Purpose : IL-17-secreting CD4⁺ T cells (Th17) have been revealed as the central player in causing autoimmune damage in dry eye disease (DED). Recent studies have shown that transmembrane CMTM6 regulates antitumor T cell responses by modulating CD58 and PD-L1 protein expression, but its function in Th17 cells remains unknown. This study aimed to investigate the role of CMTM6 in Th17 cells and experimental dry eye (DE).

Methods : We measured CMTM6 expression in human Th17 cells using the DICE database. Naïve CD4⁺ T cells isolated from C57BL/6J mice were cultured under Th17 cell-polarizing conditions. RT-PCR and flow cytometry were used to analyze the expression of CMTM6. The impact of CMTM6 on the activation of naïve CD4⁺T cells, as well as on the proliferation and differentiation of Th17 cells, was evaluated by flow cytometry. Dry eye (DE) models were established in both wild-type and Cmtm6^fl/flCD4^cre mice through subcutaneous injection of scopolamine. Tear secretion was measured using the phenol red thread test, and ocular surface damage was assessed with fluorescein sodium staining scores. Flow cytometry was utilized to determine the proportion of Th17 cells in draining lymph nodes (DLNs). RT-PCR was employed to detect the expression of Th17-associated inflammatory cytokines and transcription factors in corneal and conjunctival tissues.

Results : Analysis from the DICE database shows high expression of CMTM6 in human Th17 cells. CMTM6 is highly expressed during the differentiation of Th17 cells in vitro, similarly, an upregulation of CMTM6 is noted in Th17 cells in the conjunctiva, lacrimal glands, and DLNs in experimental DE. Cmtm6 deficiency promotes the differentiation of Th17 cells but does not affect the activation of naïve CD4⁺ T cells or the proliferation of Th17 cells. Specific deletion of Cmtm6 in T cells enhances Th17 cell differentiation in DLNs and exacerbates symptoms of DE by increasing Th17 cell-mediated inflammation.

Conclusions : Our studies indicate that CMTM6 alleviates inflammation in DE by reducing Th17 cell differentiation. CMTM6 may be a potential therapeutic target for Th17-driven autoimmune diseases.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

CMTM6 is highly expressed in Th17 cells. (LG, lacrimal gland; DLNs, draining lymphocytes.)

 

CMTM6 inhibits Th17 cell differentiation and autoimmune inflammation. (WT, wild type; KO, Cmtm6^-/-.)