Contact-dependent determinants of human natural killer cell development

Abstract: Human natural killer (NK) cells are traditionally identified as CD56+CD3- large granular innate lymphocyte that can detect and eliminate virally infected and malignant cells. Although CD56 is used to identify NK cells, its function is not fully understood. CD56 or neural cell adhesion molecule (NCAM) was first described in neural progenitor cells where it can engage in homotypic and heterophilic interactions with its ligands (e.g., NCAM, fibronectin domains, sulfate proteoglycans) and regulates neuron survival, migration, and development. Interestingly, both xenogenic murine developmentally supportive stroma (e.g., EL08.1D2 and OP9) commonly used for in vitro NK cell differentiation from CD34+ progenitors and stromal cells in sites of hematopoiesis (e.g., bone marrow MSC) express NCAM when compared non-developmentally supportive stroma. Furthermore, work published in the Mace Lab has revealed that inhibition of CD56 (NCAM) mediated interactions between NK cells and stromal cells by a blocking antibody perturbs in vitro NK cell development resulting in decreased NK cell number and migration. I hypothesize that Ncam on developmentally supportive stromal cells and CD56 on NK cells mediate interactions between stromal cells and NK cells that are required for NK cell development, survival and proliferation. My first aim is to characterize the functional role of Ncam expression on developmentally supportive stroma. My preliminary data suggests that the use of Ncam1 knockout murine EL08.1D2 stromal cells for in vitro NK cell differentiation leads to decreased NK cell developmental intermediate survival, proliferation, and migration. I will determine whether Ncam, on developmentally supportive stroma, mediates their ability to support NK cell development, survival, and migration. My second aim is to define the requirement of CD56 on human NK cells for their development and migration. Work by the Mace lab has shown that inhibition of CD56 on NK cells, via blocking antibody, leads to a decrease in cell migration and dysregulation of the actin cytoskeleton. I will delete CD56 in human NK cell progenitors and follow their development in vitro by transcriptomic and phenotypic analysis. Together our study will bring light to a previously unknown CD56 mediated interactions and signaling pathways required for human NK cell proliferation, survival and migration through development.