Sections (5 μm) of paraffin-embedded irradiated skin sections were cut and immunostained to identify neutrophils with rat anti-mouse neutrophil antibody (Serotec, Raleigh, NC) at 0.5 μg/ml and macrophages with rat anti-mouse Mac-3 (BD PharMingen, San Diego, CA) at 2.5 μg/ml as previously described.^9,10 Briefly antigen-antibody complexes were detected using the Vectastain Elite rat ABC peroxidase kit (Vector Laboratories, Burlingame, CA) according to the manufacturer’s instructions and were visualized with diaminobenzidine/H₂O₂. Total immunostained cells were counted in five ×400 high-power fields (HPFs) in the irradiated skin and expressed as mean ± SEM. Mast cells were identified by staining with low pH toluidine blue and counted in five ×400 HPFs. Significant intergroup differences were determined by applying the two-tailed assuming unequal variance t-test. Immunostaining for keratinocyte-derived cytokine (KC) and macrophage inflammatory protein-2 (MIP-2) were performed using a similar protocol with anti-mouse KC (Antigenix America, Inc., Huntingtion Station, NY) and anti-murine MIP-2 (Chemicon International, Temecula, CA) both at an IgG concentration of 1 μg/ml.