Tu169 - Retinoic Acid-related Orphan Receptor Alpha Expression Differentiates Distinct Populations of Human Group 2 Innate Lymphoid Cells

Sarah Colpitts, MSc – PhD Graduate Student, Immunology, University of Toronto; Jessica Mathews, MSc – Ajmera Transplant Centre and Toronto General Hospital Research Institute – University Health Network; Jana Gillies – BC Children’s Hospital Research Institute; Megan Levings, PhD – Department of Surgery – University of British Columbia; Sarah Crome, PhD – Ajmera Transplant Centre and Toronto General Hospital Research Institute – University Health Network

Abstract Text: Group 2 innate lymphoid cells (ILC2s) are innate lymphocytes with central roles in host defense and tissue homeostasis. ILC2s are defined by expression of transcription factor GATA-3 and production of type 2 cytokines IL-4, IL-5, IL-9, and IL-13. A subpopulation of ILC2s has also been shown to produce IL-10. Recently, these IL-10 producing ILC2s (ILC210) were shown to limit T cell responses in contexts including islet transplant, helminth expulsion and allergic rhinitis. Transcription factors that promote protective or pathogenic functions of human ILC2s are not well defined, particularly those that underlie IL-10 expression by ILC2s. Murine studies have demonstrated a crucial role for RORA in ILC2 development, yet the role of RORA in differentiated human ILC2 function is unknown. Here we show that ex vivo expanded human ILC210 from peripheral blood express RORA by single cell RNA sequencing and flow cytometry, but exhibit little to no GATA3 expression, whereas ILC2s that lack IL-10 production express GATA3. In ex vivo expanded ILC2s, protein level RORA expression positively correlates with IL-10 production, with ILC2s still maintaining high expression of IL-4, IL-9, and IL-13. Using a lentiviral gene transfer system, we are currently examining effects of enforced RORA expression on differentiated ILC2s, including downstream gene programs and expression of ILC-associated cytokines compared to effects of ILC1 and ILC3-associated transcription factors TBET and RORC2. Collectively, these efforts aim to define the role of RORA in the function of differentiated human ILC2s and to better understand transcriptional programs that underlie IL-10 production by ILC2s.