P815-based redirected degranulation assay to study human NK cell effector functions

Natural killer (NK) cells are part of the innate immune system, the classic cytotoxic population of innate lymphoid cells (ILCs). They can directly kill virus-infected or tumor cells through different mechanisms without prior sensitization using their lytic functions in response to different signals (target cell ligands and/or inflammatory cytokines) and secreting cytokines, such as interferon gamma (IFNγ) and tumor necrosis factor (TNF). NK cells use antibody-dependent cell-mediated cytotoxicity (ADCC) to recognize and kill cells expressing target antigens when they are antibody coated. Redirected cytotoxicity is a technique used to target cells that do not per se activate NK cells. Here, we use redirected degranulation, a surrogate technique that correlates with redirected lysis. The P815 cell line (mouse mastocytoma) express fragment crystallizable gamma receptor II (FcγRII) and therefore could bind the Fc portion of mouse IgG antibodies, which through their fragment antigen-binding (Fab) may recognize NK cells activating receptors leading to target cell lysis. This technique could be used to determine the inhibitory or activating capacity of different receptors or isoforms and in immunotherapy using T cell and NK cell activators.