The Effect of X Irradiation on Alveolar Macrophages in Mice

Abstract

The number and DNA labeling index of alveolar macrophages and interstitial precursor cells was studied in mice up to 3 months after thoracic irradiation. Doses of 2 and 5 Gy produced a 60% fall in numbers of lavageable macrophages within 3 days with a return to control levels by 16 days and 8 weeks, respectively. A dose of 10 Gy produced a more prolonged suppression with a return to control levels by 8 weeks. Examination of histological sections showed a decrease in macrophage numbers only after 10 Gy. The labeling index of lavaged macrophages fell rapidly from the control value (2.4%) to zero 1 day after irradiation. The time for recovery to the control level was again dose-dependent. Macrophages in sections showed the same fall and subsequent recovery in labeling index followed by a substantial overshoot. Alveolar wall cells, believed to be macrophage precursors, showed only slight fall in labeling index followed by an increase above control levels which was most marked after 10 Gy. The results indicate that radiation induces a depletion in the mature macrophage population and a proliferative response among interstitial precursor cells and immature macrophages. The effect is dose-dependent up to 10 Gy.