IL17A and pneumonitis: Given the increased frequency of Th17 cells in the lungs of mice manifesting distress due to radiation-induced pneumonitis with fibrosis, which was not evident in mice succumbing with pneumonitis only, we sought to determine whether a deficiency in interleukin-17A (Il17), an effector molecule of Th17 cells28, affects the development of radiation induced fibrotic lung disease.