DEFA5-producing CD4 + T cells in the intestines of atopic dermatitis patients play an important role in the development of AD-associated intestinal inflammation

Kai Zhuang^1,2,3Mengjun Li^1,2,3Yalan Wu^1,2,3Yi Luo^1,2,3Jian Song^1,2,3Sze Chun Leo CHAN^4,5Jinmei Li^1,2,3Ziying Chen³Yulin Ouyang⁶Yongliang Zhang^4,5*Ying Lin^7,8,9*Huanhuan Luo^1,2,3*

• ¹State Key Laboratory of Traditional Chinese Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
• ²Chinese Medicine Guangdong Laboratory, Guangdong Hengqin, 519031, China, Zhuhai, China
• ³College of Basic Medicine, Guangzhou University of Chinese Medicine, Guangzhou, China
• ⁴Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
• ⁵Immunology Programme, Life Sciences Institute, National University of Singapore, Singapore, Singapore
• ⁶School of Pharmaceutical Science, Guangzhou University of Chinese Medicine, Guangzhou, Guangdong Province, China
• ⁷Department of Dermatology, The Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong Province, China
• ⁸Guangdong Provincial Key Laboratory of Chinese Medicine for Prevention and Treatment of Refractory Chronic Diseases, Guangzhou, Guangdong 510120, China, Guangzhou, China
• ⁹Guangdong Provincial Clinical Research Center for Chinese Medicine Dermatology, Guangzhou, Guangdong 510120, China, Guangzhou, China

Atopic dermatitis (AD) is associated with various gastrointestinal symptoms, with underlying mechanisms remain poorly understood. In this study, through analysis of the cellular atlas of the intestines of patients with AD, we identified specific groups of CD4+ intraepithelial lymphocytes (IELs) capable of producing defensin alpha 5 (DEFA5) in the small intestine, and this groups of IELs may play important roles in mediating the development of intestinal inflammation in AD. Single-cell RNA sequencing was employed to analyzed immune cells composition in the ileum of AD patients and a pronounced upregulation of DEFA5 in CD4+ T cells in AD patients were identified. The DEFA5-expression CD4+ T cells were enriched in tissue central memory T cells (Tcm) and tissue resident memory T cells (Trm). It was also found that the peroxisome proliferator-activated receptor (PPAR) signaling pathway may plays important role in the expression of DEFA5 by CD4+ IELs. Using a mouse model of AD, it was confirmed that AD was associated with increased DEFA5-expressing CD4+ IELs which contributes to the damage of intestinal barrier function and the development of inflammation. These findings indicate that AD was associated with an increase in intestinal DEFA5-expressing CD4+ IELs which may play an important role in the development of intestinal inflammation.