Varied effects of thoracic irradiation on peripheral lymphocyte subsets in lung cancer patients

To investigate the influence of thoracic irradiation on immunological competence in patients with lung cancer, we examined the changes in peripheral blood lymphocyte subsets in 15 patients before and after radiation therapy by two-color flow cytometry techniques. After radiation therapy, the percentage and the absolute number of CD4+CD45RA+ cells (naive T cells) and CD56+ and/or CD16+ cells (NK cells) decreased. The percentage of CD4+human leukocyte antigen-DR(HLA-DR)+ cells (activated CD4T cells) and CD8+HLA-DR+ cells (activated CD8T cells) increased, although the absolute number did not change significantly. Naive T cells may be more selectively damaged than memory T cells by thoracic irradiation, through their recirculation behavior. The reduction of natural killer (NK) cells is disadvantageous for anti-tumor immunity. The percentage of HLA-DR positive T lymphocytes was significantly increased, and thus the possibility of HLA-DR enhancement by irradiation cannot be excluded. Therefore, thoracic irradiation has numerous varied effects on the immunological system of lung cancer patients.