Interleukin-23 is Essential for Development of Pathogenic Memory T Helper-17 Cells in Chronic Dry Eye Disease

Abstract

Purpose : Following the progression of dry eye disease (DED) to the chronic phase, the predominant effector T helper (Th) 17 cells switch to long-term surviving memory Th17 (mTh17) cells. We have shown that these mTh17 cells are primarily responsible for sustaining chronic inflammation in DED, and are maintained by interleukin (IL)-7 and IL-15. However, it is unknown how these mTh17 cells are developed from their effector precursors. This study investigated the requirement for IL-23 and IL-2 signaling in the development of mTh17 cells in a mouse model of DED.

Methods : Acute DED was induced by exposing C57BL/6 mice to environmental desiccating stress for 14 days. Effector T cells (CD62L^-CD44^loCD4⁺) from the draining lymph nodes of acute DED mice were isolated using FACS sorting, and cultured in the presence of IL-23 (10ng/mL), IL-2 (50IU/mL), CD25 blocking antibody (mAb) (10μg/mL), IL-23+IL-2, or IL-23+CD25 mAb for 48 hours. The frequencies of mTh17 cells (CD44^hiIL-17A⁺CD4⁺), expression levels of IL-7 and IL-15 receptors, as well as Annexin V and Ki-67 by Th17 cells were then assessed using flow cytometry. Furthermore, IL-23 signaling was blocked by intraperitoneal injection of anti-IL-23R Ab at day 14 when acute DED mice were returned to the normal environment. The disease severity was then evaluated for 7 days by corneal fluorescein staining (CFS), and mTh17 cells were examined using flow cytometry.

Results : After 48 hours of culture of DED effector T cells, the frequencies of generated mTh17 cells were significantly higher in the presence of IL-23 (54±3%; p < 0.001), CD25 mAb (35±1%; p < 0.001), or IL-23+CD25 mAb (65±1%; p < 0.001) than those cultured in the media alone (23±1%). In addition, IL-23, CD25 mAb, and IL-23+CD25 mAb all dramatically enhanced the expression of IL-15R (MFI = 85, 64, 97 respectively vs. 8 in media alone), while suppressing Annexin V expression by Th17 cells (MFI = 70, 67, 23 respectively vs. 134 in media alone). In vivo blockade of IL-23 signaling prevented the development of mTh17 cells from existing effector Th17 cells by 30% (p = 0.019), and significantly decreased ongoing disease severity by 33% (p = 0.004).

Conclusions : IL-23 is required for the development of pathogenic memory Th17 cells in chronic DED by up-regulating IL-15 receptor expression and preventing apoptosis of Th17 cells.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.