The effects of splenic irradiation on lymphocyte subpopulations in chronic B‐lymphocytic leukemia

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Abstract
We describe the effect of splenic irradiation (SI) (0,5–1 Gy weekly) on lymphocyte subpopulations for 7 patients with progressive B chronic B‐lymphocytic leukemia (B‐CLL). Using specific cellular characteristics we could distinguish normal from abnormal cells. The irradiation resulted in a decrease of lymph node size, reduction in spleen volume and decrease in peripheral blood lymphocytes. The one exception was a patient with a prolymphocytoid transformation of B‐CLL. For 3 patients SI had to be interrupted or stopped because of severe cytopenia. Quantitation of malignant B cells and normal T lymphocytes revealed that the total irradiation dose which resulted in a specific decrease of malignant lymphocytes varied from patient to patient. Normal T‐cell subpopulations, which were increased before SI, decreased to normal or abnormally low values during SI. In previously untreated patients, natural killer (NK) cell numbers decreased more rapidly than T‐cell subpopulations. For 2 patients refractory to chemotherapy an increase of NK cells was observed upon SI.