CXCL4 and CXCL4L1 attract activated T lymphocytes and NK cells. Chemotaxis experiments were performed to compare the chemotactic activity of CXCL4 and CXCL4L1 for (A) human (h) IL-2–activated T lymphocytes (n = 4 to 5), (B) murine (m) IL-2–activated T lymphocytes (n = 4 to 5), and (C) unstimulated NK cells (n = 5). Statistically significant migration toward chemokine is indicated (*P < .05; **P < .005; Mann Whitney test).