IFNλ promotes IFNγ⁺ NK cell responses.

<p>(A) Neutrophil numbers in the spleens and livers of mCMV-infected WT and <i>Ifnλr1</i>^<i>-/-</i> mice was assessed 4 days p.i. IFNγ⁺ (B&D) and granzyme B⁺ (C&E) NK cell accumulations in spleens (B-C) and livers (E&F) were quantified day 4 pi. Individual mice + mean is shown from 2 independent experiments and represent 4 (liver) or 5 (spleen) experiments in all. (D) Representative bivariant FACS plots of IFNγ versus granzyme B expression by live NK1.1⁺CD3^- cells 4 days post-infection. Plots show concatenated samples from 4 (WT) and 6 (<i>Ifnλr1</i>^<i>-/-</i>) mice. Results represent 3 experiments. (G) IFNγ protein in the serum was measured 4 days pi. Mean + SEM of 3–4 mice/group is shown. (H&I) IL-12 (H) and IL-18 (I) protein was measured in naïve spleen tissue or after 2 days of mCMV infection. Mean + SEM of 3 (naïve) or 7 (infected) mice is shown. (J) IFNγ expression by NK cells stimulated with IL-12, IL-18 or IL-12/IL-18 +/- IL-28A was detected by flow cytometry. Data represent the mean +/- SD for 3 mice per group. All experiments were performed at least twice.