Changes in peripheral blood lymphocyte subsets in patients undergoing radiotherapy.

Purpose: To investigate the changes in peripheral blood lymphocyte subpopulations in patients undergoing radiotherapy. Materials and methods: In 8 patients undergoing external beam radiotherapy to the pelvis, the different lymphocyte subpopulations were followed during treatment. The lymphocyte populations were determined using two-colour flow cytometry. The study comprises the T-helper, T-suppressor/cytotoxic cells, the B-lymphocytes and natural killer (NK) cells. Results: The B-cells were characterized by a steep decrease at the beginning of the radiotherapy. They reached their lowest level at an equivalent total body dose of 1.5Gy and remained constant during the rest of the therapy (10% of the initial level). In T-cells (both T-helper and T-suppressor subsets) the steep decrease was less pronounced. T-lymphocytes reached a base level at 2.5Gy equivalent total body dose (20% of the initial level). No significant differences between the T-helper and the T-suppressor/cytotoxic cells were observed. NK cel...