To confirm that systemic delivery of an IL-13 depleting agent was capable of preventing radiation fibrosis, and to validate that IL-13Rα2 saturation could guide the timing of therapy, irradiated wild type mice were treated with murine IgG targeting IL-13 (0.5 mg per animal) or an isotype control (Genentech, San Francisco, CA) with weekly dosing beginning at week 3 after irradiation and continuing through week 8. The gene discussed is IL13; the disease is radiation pneumonitis.