Organization of the chemokine superfamily and some of their members. BCA-1, B-cell-attracting chemokine 1; IL-8, interleukin-8; IP-10, interferon-inducible protein 10; MCP, monocyte chemoattractant protein; MIP, macrophage inflammatory protein; RANTES, regulated on activation, normal, T-cell expressed, and secreted; SDF-1, stromal-cell-derived factor 1.