Oral Presentation CD1-MR1 Workshop 2025

Subsets of regulatory T cells are CD1a-reactive and dysfunctional in psoriasis (#30)

Lea Nussbaum 1 , Rosana Ottakandathil Babu 1 , Emily Zhi Qing Ng 2 , Jessica Soo Weei Ng 1 , Rachel Etherington 1 , Karmella Naidoo 1 2 , Janina Nahler 1 , Fei Gao 1 2 , Prathiba Kurupati 1 , Tao Dong 1 2 , Hashem Koohy 1 , Graham Ogg 1 2 , Yi-Ling Chen 1 2
  1. MRC Translational Immune Discovery Unit (TIDU), MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
  2. CAMS Oxford Institute, University of Oxford, Oxford, UK

Regulatory T cells (Tregs) contribute to skin homeostasis, but the antigenic targets remain unclear. The infiltration of Tregs is coincident with CD1a-expressing cells during skin inflammation, and whilst CD1a is known to present lipid antigens to effector T cells, the extent to which CD1a presents lipid antigens to Tregs has not been investigated. Here, we show CD1a reactivity in subsets of human circulating and cutaneous CD4+ Tregs, displaying ab T cell receptors (TCRs), memory phenotypes and suppressive functions, including the ability to secrete interleukin-10 (IL-10) in response to the permissive lipid antigen lysophosphatidylcholine, known to be enriched in skin inflammation. Next, single-cell CITE-seq analyses of CD1a-reactive IL-10–producing CD4+ Tregs from psoriatics showed maintenance of some canonical characteristics including LAG-3+CD49b+ expression, but with altered pro-inflammatory signatures including up-regulated type 1 and 17 effector function. In addition, clonally expanded IL-10–producing Tregs retained their suppressive phenotype in a CD1a- and TCR-dependent manner. Together, these findings show that subsets of Tregs are directed to self-lipid antigens and CD1a, but show an altered phenotype equipped with pro-inflammatory potential in the setting of psoriasis.