CXCR4 and Decreased total neutrophil count: Finally, the still-debated questions of the sources of neutrophils mobilized by AMD3100 together with neutrophil heterogeneity (spatial, phenotypic and functional) have prompted doubts about neutrophil sequestration in the BM as the sole mechanism to explain neutropenia driven by the WHIM-associated gain of CXCR4 function.