LAUSR

Natural Killer (NK) cells have been characterized as cytotoxic lymphocytes that are key in regulating viral infections and combatting cancer. In contrast to B and T cells, there has not been a detailed examination of the developmental trajectory of human NK cells. Conflicting reports in literature state that NK cells can develop from both lymphoid and myeloid cell progenitors. Here, we utilized mass cytometry (CyTOF) to perform a multiplexed analysis of NK cell development on healthy human bone marrow. To address the current gap in knowledge, we built a comprehensive CyTOF panel to include lymphoid markers, myeloid markers, and various regulatory factors shown to be important both in mouse and human NK cell development across 4 donor samples. We analyzed this data with multiple supervised and unsupervised single cell trajectory algorithms in order to model NK developmental processes. This approach allows for unbiased observations across developmental lineages and the reconciliation of the conflicting literature. The ability to simultaneously measure multiple cellular features, including phenotypic proteins, transcription factors, and regulatory enzymes allowed us to identify a novel potential NK lineage-restricted progenitor in adult human bone marrow. We have found potential CD34+ NK progenitors with different combinations of surface markers previously used to identify NK progenitors and regulatory markers such as IRF8, NFIL3, ID2 and TdT. Our findings here show that NK cells may be generated through two distinct fate pathways. Our next step is to analyze the capacity of this novel progenitor subpopulation to generate mature and functional CD56+ NK cells in vitro, through co culture with the OP9 and OP9-DL4 cell lines. Ultimately, our studies will shed light on the knowledge of early stages of NK lineage commitment.