To examine CXCR4 function, we tested three different CXCR4 antagonists: (1) the bicyclam AMD070 (X4P-001, mavorixafor), which is a selective CXCR4 antagonist; (2) the bicyclam AMD3100 (plerixafor), which has therapeutic potential in HIV infection and inflammatory diseases including WHIM syndrome as well as in cancer and stem-cell mobilization [47, 48]. This evidence concerns the gene CXCR4 and WHIM syndrome.