The Effector Differentiation of TCRaß+CD8aa+ Intraepithelial Lymphocytes Is Reciprocally Regulated by BCL6 and BLIMP1

CD8aa+TCRaß+ intraepithelial lymphocytes (IELs) play crucial roles in maintaining intestinal homeostasis and host protection. However, the functional regulation of these cells remains unclear. Here, we have discovered and characterized two distinct developmental stages within intestinal CD8aa+ aß IELs: a stem-like, defined by BCL6, TCF1 and CD160 expression, and an effector-like, with Granzyme B expression and Prdm1 transcription, by sorting and transcriptional sequencing BCL6+CD160+ CD8aa+ aß IELs and BCL6-CD160- CD8aa+ aß IELs. Comparing transcriptional profiles of total CD8aa+ aß IELs from BCL6-deficient, BLIMP1-deficient and TCF1-deficient mice compared with that from their WT littermate control mice, we found a critical antagonistic function between BCL6/TCF1 and BLIMP1 in governing the fate decisions of CD8aa+ aß IEL subsets. Overall design: RFP+CD160+ CD8aa+ aß IELs and RFP-CD160- CD8aa+ aß IELs were isolated from small intestine of steady state Bcl6RFP mice for bulk RNA-seq. Total CD8aa+ aß IELs were isolated from small intestine of steady state Bcl6fl/flCd8cre, Prdm1fl/flCd8cre and Tcf7fl/flCd8cre mice and their littermate WT control (Bcl6fl/fl, Prdm1fl/fl and Tcf7fl/fl) mice for bulk RNA-seq.