Splenic irradiation in myelofibrosis: effect on circulating myeloid progenitor cells.
We have investigated the mechanism of splenic irradiation-induced granulocytopenia in two patients with myelofibrosis and marked splenomegaly. Serial assays were performed for circulating granulocyte-monocyte progenitors capable of colony formation in vitro (CFU-C). For comparison, similar studies were performed on two patients receiving whole brain irradiation for glioma. Splenic irradiation caused a significant decrease in circulating CFU-C in the myelofibrosis patients. There was no decrease in circulating CFU-C in the brain-irradiated patients. No radiation-induced humoral inhibitor of granulopoiesis and no increased CFU-C radiosensitivity could be demonstrated in the myelofibrosis patients. These observations, taken together with previous data on splenic blood flow and pooling, suggest that the major mechanism of irradiation-induced granulocytopenia in myelofibrosis is destruction of proliferating precursor cells in the splenic tissue and sinusoids.
D000368:Aged; D000380:Agranulocytosis / Q000209:etiology*; D001921:Brain / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D006801:Humans; D007958:Leukocyte Count; D009504:Neutrophils; D055728:Primary Myelofibrosis / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology*; D011878:Radiotherapy / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D013154:Spleen / Q000528:radiation effects*