Production of IFN-γ by NK cells is cell-contact dependent.

<p>A) R2 macrophages (Mφ) were either left untreated or infected with <i>L. monocytogenes</i> (LM) for 24 hrs prior to co-incubation with freshly isolated splenic lymphocytes for another 18 hrs. Alternatively, splenocytes were incubated with supernatants from infected R2 macrophages alone. As negative and positive controls, splenocytes were stimulated with IL-2 alone or IL-2 + IL-12, respectively. IFN-γ production by NK cells was measured by intracellular FACS staining gating on NKR-P1A⁺CD3⁻ NK cells. B) Measurement of IL-1α, IL-6, IL-12p70, and TNF-α in the supernatants of uninfected or infected R2 macrophages cultured for 24–72 hrs was done with multiplex cytokine assay analysis.