Repeated intradermal administration of recombinant mMCP-11 in the ear skin induces leukocyte infiltration in a protease activity–dependent manner. WT mice were treated 3 times at 24-hour intervals with intradermal administration of 10 μg WT mMCP-11 (black bars), inactive mutant (MT) mMCP-11 (dark gray bars), or control BSA (light gray bars) each time. The numbers of cells (total, CD45⁺ cells, and indicated leukocyte types) isolated from the ear skin at 4 hours postchallenge are shown (mean ± SD, n = 3 ears each). Data shown are representative of 3 independent experiments. *P < .05; **P < .01; ***P < .001.