Interleukin-27 Signalling Induces Stem Cell Antigen-1 Expression In T Lymphocytes Invivo

Stem cell antigen-1 (Sca-1/Ly6A/E) is a cell surface glycoprotein that is often used as a biomarker for stem cells and cell stemness. However, it is not clear what factors can directly induce the expression of Sca-1/Ly6A/E in T lymphocytes invivo, and if induction of Sca-1 is associated with T cell stemness. In this study, we show that interleukin-27 (IL-27), a member of the IL-12 family of cytokines, directly induces Sca-1 expression in T cells invivo. We found that mice-deficient for IL-27 (either P28 or EBI3) or its signalling (IL-27R) had profound reduction of Sca-1 expression in naive (CD62L(+)CD44(-)), memory (CD62L(+)CD44(+)) and effector (CD62L(-)CD44(+)) T cells. In contrast, invivo delivery of IL-27 using adeno-associated viral vectors strongly induced the expression of Sca-1 in naive and memory/effector T-cell populations in an IL-27 receptor- or signal transducer and activator of transcription 1-dependent manner. Interestingly, IL-27-induced Sca-1(+) T cells do not express or up-regulate classic stem cell-associated genes such as Nanog, Oct4, Sox2 and Ctnnb1. However, IL-27-induced Sca-1(+) T cells had increased expression of effector/memory-associated transcription factor T-bet, Eomes and Blimp1. Hence, IL-27 signalling directly induces the expression of Sca-1/Ly6A/E expression in T cells. Direct expansion of Sca-1(+)CD62L(+)CD44(-) T memory stem cells may explain why IL-27 enhances T-cell memory.