Assuming that CXCR4 in GC B cells polarizes on the cell’s leading edge in the presence of its ligand CXCL12, as has been reported for T cells and several CXCR4 expressing cancer cell lines (69, 70), higher absolute numbers of CXCR4 receptors entail an advantage to compete for space on CXCL12 presenting reticular cell networks (or immobilized CXCL12 on other surfaces) in the DZ (Figure 3G). The gene discussed is CXCR4; the disease is cancer.