The effect of radiotherapy on blood mononuclear cell numbers and phagocyte migration.

The effect of localised radiotherapy on whole blood mononuclear cell numbers are on phagocyte migration has been studied in order to relate the effects of treatment to site and volume of radiation. Thirty nine patients who were receiving radiotherapy to five different sites were studied sequentially before, during, and after treatment. Lymphopenia developed with the onset of treatment in the four groups treated with radiotherapy to a large volume. The fall in lymphocyte count affected both T cells and non-T cells, was exponential throughout the period of irradiation, and the rate was independent of site of treatment. Monocyte numbers and phagocyte migration was unaffected. T cells were slightly more radiosensitive than non-T cells and recovery of T cell numbers was usually slow. No effect was seen when superficial radiotherapy was given to a small volume of skin.