Figure 4.

FHL2 deficiency decreases S. pneumoniae-induced IFNγ production by natural killer (NK) cells. Mice were infected i.n. with 5 × 10⁵ cfu (LD50) S. pneumoniae. (A) The protein expression of IFNγ was determined by ELISA in the bronchoalveolar lavage obtained from wild-type (WT) and FHL2^−/− mice, 24 h postinfection. Results of two distinct experiments are shown. (B,C) qRT-PCR was performed to assess the mRNA expression of (B) IFNγ and (C) CXCL9 and STAT1 in total lungs obtained from WT and FHL2^−/− mice, 24 h postinfection. Experiment representative of two independent experiments. (D) Intracellular IFNγ levels in lung NK cells were detected using flow cytometry (n = 5). (A–D) Each dot represents the data from 1 mouse. *p < 0.05, **p < 0.01 by Mann–Whitney test. (E) FHL2^−/− mice were untreated (black circle) or i.p. injected (gray plot) with rmIFNγ (10 μg/mouse) twice, at the time of infection and 48 h postinfection. (F) Purified NK cells from IFNγ^−/− mice (IFNγ^−/− NK cells → FHL2^−/− mice; black plot) or WT mice (WT NK cells → FHL2^−/− mice; gray circle) were i.v. injected in FHL2^−/− recipient mice at the time of infection. (E,F) Survival is shown for two or three independent experiments pooled together. Statistical analysis was performed using the Mantel–Cox test (**p < 0.01). The surviving mice were kept until day 10 postinfection. None died after day 7.