Pharmacologically induced CXCR2 LOF in mice recapitulated multiple phenotypic features analogous to those observed in patients with CXCR2 LOF, including peripheral blood neutropenia, an elevated myeloid/erythroid ratio (M/E ratio), and neutrophil accumulation with myelokathexis-like (MK-like) morphology in BM, and increased pneumonia susceptibility. This evidence concerns the gene CXCR2 and susceptibility to pneumonia measurement.