Activation of tissue-resident NK and conventional NK are fundamentally different as indicated by their particular genesets

Residential natural killer cells in peripheral tissues (trNK) act as pioneering responders during infectious challenges, and thus have attracted increasing attention recently. However, their discrimination with conventional NK (cNK) cells is still problematical, limiting the further knowledge of this particular NK subgroup. Here, through an integrative transcriptome comparison of the two NK subgroups from different tissues, two genesets are defined to efficiently distinguish them. From these genesets, we have also discovered a fundamental difference of the two NK subgroups in activation. Transcriptomic profiling of trNK and cNK activated in vivo after MCMV infection and in vitro by PMA/ionomycin stimulation further confirms this difference, and reveals a particular role of chromatin landscape in regulating the trNK activation. Additionally, trNK and cNK respectively highly express IL-21R and IL-18R, indicating that their activation is differentially regulated by cytokine milieu. Indeed, IL-21 is particular critical in accessorily promoting trNK activation, while IL-18 mainly facilitates cNK activation. Further, IL-21 is found to direct transcriptome changes in activated trNK using a bunch of bifunctional transcription factors. Together, our study sheds light on the bona fide difference between trNK and cNK, which will enrich our understanding of their distinct functionalities during immune responses. RNA-Seq was performed on trNK and cNK from liver, uterus, salivary glands and spleen. RNA-Seq was also performed on ex-vivo trNK and cNK stimulated with and without PMA/Ionomycin, PMA/Ionomycin+IL-21, PMA/Ionomycin+IL-18.ATAC-seq was performed on ex-vivo trNK stimulated with and without PMA/Ionomycin, PMA/Ionomycin+IL-21.