Mechanistically, the protective value of CCR5 has been largely attributed to its regulatory effect on leukocyte trafficking to the site of infection, although additional functions of CCR5 in the immune response involving antigen recognition [36], [40], [41], priming and proliferation of lymphocytes [33], [36], [37], [40]–[44], and T cell memory formation [32], [45] have also been recognized. The gene discussed is CCR5; the disease is infection.