Abstract B153: Human NK cell distribution memory and residence in tissue sites

Abstract

Natural killer (NK) cells are innate immune cells with the ability to kill tumor cells without prior exposure. NK cells express multiple activating and inhibitory receptors in addition to the low-affinity immunoglobulin G binding receptor CD16. Accumulating evidence implicates a role of NK cells in not only direct killing of tumor cells, but also in cancer immunosurveillance and preventing metastasis to tissues sites. However, at present the distribution, diversity and tissue driven differences in NK cell function are not well characterized which may have an implication on the anti-cancer potential of tissue NK cells. Through collaboration with LiveOnNY our local organ procurement organization, we receive blood, bone marrow (BM), lung, intestines, tonsil and associated lymph nodes (LN) from research consented organ donors. Here we used this unique tissue resource to investigate the distribution, phenotypic, functional and transcriptional diversity of NK cell subsets in human tissues. We found that NK cells are ubiquitously distributed in human tissues comprising up to 40% of the CD45+ CD14/19- cells in blood, BM, spleen and lung, while only a small fraction (up to 2%) in the intestine and the LN. While blood, BM, spleen and lung are dominated by mature NK cells (CD56dim CD16+), majority of the NK cells in intestine and LN are immature (CD56hi CD16-). Age, sex and CMV sero-status do not show any correlation with NK cell distribution or subset frequency in tissues. Notably, NK cell subset distribution seems to drive functional differences between tissue NK cells, with lymphoid site NK cells expressing lower levels of effector molecules granzyme B, TNFα, Prf, Ifnγ and displaying reduced degranulation compared with their counterparts from blood, BM and spleen. For an in-depth analysis of tissue-mediated effects on NK cell subset functionality, we performed whole-transcriptome profiling on immature and mature NK cells isolated from blood, BM, spleen, lung and LN. Our analysis identified several effector molecules and NK cell surface receptors being differentially expressed between immature and mature NK cells. Furthermore, while mature NK cells of blood and tissues have similar transcriptional profiles, the transcriptional profiles of immature blood and tissue NK cells show tissue driven heterogeneity with differential expression of transcription factors, metabolic enzymes and NK cell surface receptors. Interestingly, the transcriptional signature of immature NK cells is reminiscent of the transcriptional signature of tissue resident memory T-cells showing increased expression of CD103, CD49a, CXCR6. We validated the expression of these markers using multiparameter flow cytometry and found that subset of immature NK cells in mucosal sites (lung and intestine) do indeed express markers of tissue residence. Additionally, by applying trajectory projection algorithm on NK cells from tissue sites, we show that resident NK cells comprise a distinct population from immature NK cells. Our study has identified novel, previously unidentified diversity of tissue NK cells. Phenotypic and transcriptional profiling data provide evidence for putative resident NK cells being present in certain tissue sites. Blood NK cells differ from their counterparts in tissues; especially, immature NK cells in tissues may be specifically trained to function in the tissue environment. Finally, due to the uniqueness of phenotypic, functional and transcriptional features of tissue NK cells, they may be more suited to fight cancer in situ in tissues. Citation Format: Pranay Dogra, Takashi Senda, Peter Szabo, Dustin Carpenter, Marta Toth, Puspa Thapa, Mark Snyder, Michelle Miron, Brahma Kumar, Donna L. Farber. Human NK cell distribution memory and residence in tissue sites [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B153.