CXCR4 and infection: In patients with chemotaxis defects (e.g., harboring inherited mutations in SBDS [21], CXCR4 [56], CXCR2 [57]), the severity of the infection complications could be explained not only by a quantitative deficiency of neutrophils but also by disturbances in the neutrophil movement towards a chemoattractant (for example, towards the focus of inflammation).