IFN-gamma production and degranulation are differentially regulated in response to stimulation in murine natural killer cells.

Activation of natural killer (NK) cells is induced via receptors like NKG2D, NKR-P1C and NKp46. This activation is balanced by interactions with inhibitory receptors. NK cell activation can lead to cytotoxicity mediated via polarized exocytosis of secretory lysosomes (degranulation) and interferon (IFN)-gamma production. We studied cell surface mobilization of a molecule present in secretory lysosomes, CD107a (LAMP-1), to monitor the relationship between degranulation of NK cells and their production of IFN-gamma at the single cell level. A comparison of responses in naive mouse NK cells and NK cells pre-activated with the type I interferon-inducer tilorone demonstrated a dramatic influence of pre-activation, allowing potent degranulation and IFN-gamma responses to NKG2D mediated stimulation that were not observed with naive NK cells. Degranulation and IFN-gamma production were performed by overlapping NK cell populations with generally higher frequencies of degranulating than IFN-gamma producing NK cells. An NK cell subset analysis based on expression of Mac-1 and CD27 revealed that immature NK cells (Mac-1(lo) CD27(hi)) are preferentially degranulating, Mac-1(hi) CD27(hi) cells perform both effector functions efficiently, while the most mature (Mac-1(hi) CD27(lo)) NK cells display reduced degranulation but with maintained IFN-gamma production.