Neutrophil numbers in the peripheral blood are increased when TBI is followed by heat treatment. Mice were left untreated (NT), treated with heat alone, with TBI alone, or with TBI followed 2 hours later with mild heating sufficient to raise their body temperature to approximately 39.5°C for 6 hours. The total number of leukocytes (A) and the total number of Ly6G⁺ cells (B-D) were calculated in C57BL/6 (A-B), BALB/c (C), and C3H/HeJ (D) mice treated with 3 Gy TBI with or without heat treatment. Neutrophil numbers were calculated using the percentage of Ly6G⁺ cells and the total leukocyte cell counts. (E) Total number of Ly6G⁺ cells was calculated in C57BL/6 mice treated with 6 Gy TBI with or without heat treatment. Each graph is representative of at least 3 separate experiments. n = 5 mice per group. Statistical analysis comparing TBI alone and TBI followed by heat treatment was performed: *P < .02 (Student t test).