The importance of showing up at the right place at the right time is instilled in leukocytes, just
as it is in each one of us, by our parents. The fact that leukocyte infiltration of a newly
established allograft typically presages the development of acute rejection is the downside
of having an exquisitely tuned and finely balanced immune system. Chemokines binding to
their receptors on leukocytes mediate the behind-the-scenes plays between antigen-
presenting cells and host T cells in lymphoid tissues, the actual here-and-now, in-your-face …