Human MAIT cells exit peripheral tissues and re-circulate via lymph in steady state conditions

Mucosal-associated invariant T (MAIT) cells recognize bacterial metabolites as antigen and are found in blood and tissues, where they are poised to contribute to barrier immunity. Recent data demonstrate that MAIT cells located in mucosal barrier tissues are functionally distinct from their blood counterparts, but the relationship and circulation of MAIT cells between blood and different tissue compartments remains poorly understood. Previous studies raised the possibility that MAIT cells do not leave tissue and may either be retained or undergo apoptosis. To directly address if human MAIT cells exit tissues, we collected human donor-matched thoracic duct lymph and blood and analyzed MAIT cell phenotype, transcriptome and TCR diversity by RNAseq. Overall design: mRNA profiles of CD8+MAIT from blood and lymph were generated by RNA-seq from four patients, in duplicate