S100A9 and cystic fibrosis: Summation of the number of total S100A8 and S100A9 staining neutrophils per B6 lung assessed revealed an almost 3-fold higher number of positive cells in the CF compared to wild-type lungs (p ≤ 0.01, in both cases) (Fig. 4), in agreement with the increased numbers of neutrophils identified by morphometric measures and the increase in levels of expression in the lungs.