ACTIVATION OF LAVAGE LYMPHOCYTES IN LUNG INJURIES CAUSED BY RADIOTHERAPY FOR LUNG-CANCER

Purpose: Radiation pneumonitis sometimes extends beyond the irradiated area of a lung and can also affect the opposite lung. Some immunologi cal mechanisms, in addition to simple direct injury of the lungs by ra diation, seem to be involved in the onset of radiation pneumonitis. To clarify such mechanisms, the effects of radiation on local inflammato ry cells in lungs, in particular, lymphocytes, were examined. Methods and Materials: A comparison was made of bronchoalveolar lavage fluid ( BALF) findings from 13 irradiated patients (RT group) and 15 nonirradi ated patients (non-RT group) with lung cancer. Patients who later deve loped radiation pneumonitis (RP group) and those who did not (RP-free group) were also compared, Using a two-color flowcytometer, radiation- induced changes in local inflammatory cells in lungs were analyzed, Th is included analyses of human leukocyte-associated antigen (HLADR) and intercellular adhesion molecule-1 (ICAM-1) expression on T-cells, whi ch are thought to be involved in cell activation and interactions betw een cells. Results: The following aspects of BALF were higher in the R T group than in the non-RT group: (a) the percentage of lymphocytes an d esinophiles; (b) the incidence of HLADR-positive CD4+T-cells and HLA DR-positive CD8+T-cells; and (c) the incidence of ICAM-1-positive T-ce lls. The following aspects of BALF were higher in the RP group than in the RP-free group: (a) the total cell counts; (b) the percentage of l ymphocytes; and (c) the incidence of ICAM-1-positive T-cells. A signif icant relationship was seen between the incidence of ICAM-1 expression on T-cells and the number of days from the initiation of radiotherapy to the onset of radiation pneumonitis. Conclusion: These data suggest that irradiation can induce accumulation of activated T-cells (HLADR and ICAM-1-positive T-cells) in the lung. This accumulation may be clo sely linked to radiation-induced lung injury. It is also suggested tha t the incidence of ICAM-1-positive T-cells in BALF may serve as a usef ul clinical marker of radiation pneumonitis.