Figure 5. The S. pneumoniae virulence protein Spr1875 elicits IL-10 production by NK cells.

Schematic of co-culture experiment with IL-10-deficient BMDCs, where BMDCs were infected or stimulated with protein prior to the addition of NK cells purified from the lungs or spleens of naïve mice (A). Supernatant IL-10 in 72 h cultures of NK cells purified from the lungs or spleens following co-culture with IL-10-deficient BMDCs infected for 1 h with S. pneumoniae (Spn) (B). Representative gel of Spr1875 protein fractions stained with Coomassie (left) and anti-His immunoblot of pooled protein fractions (right) (C). Supernatant IL-10 in 72 h cultures of NK cells purified from the lungs or spleens following co-culture with IL-10-deficient BMDCs stimulated with LPS or LPS + Spr1875 for 1 h (D). Histogram of GFP (IL-10) expression in NK cells (NK1.1⁺CD3⁻) from the lungs of IL-10 GFP reporter mice 72 h following injection with either PBS (solid grey) or Spr1875 i.t. (purple) (E). Summary of % GFP+ NK cells for each group is also shown. Lung homogenate IL-10 in PBS versus Spr1875 treated mice is compared at 72 h (F). In vitro data (B, D) are pooled from three independent experiments with technical replicates in triplicate, **p<.01, ***p<.001 as measured by t-test. In vivo data (E-F) are pooled from three independent experiments with n = 3 mice/group, **p<.01 as measured by t-test.