CXCL5−/− mice do not show much decrease in CXCR2 expression on bone marrow and blood neutrophils as compared to the wild type (WT) mice upon E. coli-induced pneumonia, but the CXCR2 expression on neutrophils remains unchanged during intranasal lipopolysaccharide (LPS) challenge (52). This evidence concerns the gene CXCR2 and susceptibility to pneumonia measurement.