CD19 and Hypercholesterolemia: The Mev pathway and the CXCL12/CXCR4 axis may reciprocally affect their activity, as shown by at least two observations: 1) for optimal signaling CXCR4 must be incorporated into membrane lipid rafts, whose formation require membrane cholesterol, and which orchestrate the interaction of the small GTPases Rac and Rho with their downstream transducers [31]; 2) hypercholesterolemia induces the secretion of CXCL12 and drives the migration of CD19+/CXCR4+ B lymphocytes from the bone marrow to the peripheral blood by interfering with the CXCL12/CXCR4 axis [32].