IL18 and influenza: Postvaccination enhancement of NK cell IFN‐γ production was dependent on IL‐2 produced from CD4+ T cells, whilst degranulation responses were dependent on IL‐2 and on the presence of anti‐influenza antibody.13, 23 A costimulatory role for innate myeloid cell‐derived cytokines was also demonstrated by partial inhibition of TIV restimulation responses with IL‐12, IL‐18 and IFN‐αβR2 blockade.13