T cell receptor is required for differentiation but not maintenance of intestinal CD4+ intraepithelial lymphocytes

The gut epithelium is populated by intraepithelial lymphocytes (IELs), a heterogeneous T cell population with cytotoxic and regulatory properties, which can be imprinted on CD4+ T cells at the epithelium. However, the role of the T cell receptor (TCR) in this process remains unclear. Single-cell transcriptomic analyses revealed distinct clonal expansions between cell states, with CD4-IELs being one of the least diverse populations. Conditional deletion of TCR on differentiating CD4+ T cells or of MHCII on intestinal epithelial cells prevented CD4-IEL differentiation. However, TCR ablation on differentiated CD4-IELs, or long-term cognate antigen withdraw, did not affect their maintenance. TCR re-engaging of antigen-specific CD4-IELs during Listeria monocytogenes infection did not alter their state but correlated with reduced bacteria invasion. Thus, local antigen recognition is an essential signal for differentiation of T cells at the epithelium but differentiated CD4-IELs are able to preserve an effector program in the absence of TCR signaling. Overall design: Full transcriptome profiles of bulk populations and single cells of intraepithelial lymphocytes (IELs) with TCR repertoire of single cells.