Changes of lymphocyte subsets after local irradiation for early stage breast cancer and seminoma testis: long-term increase of activated (HLA-DR+) T cells and decrease of "naive" (CD4-CD45R) T lymphocytes.

Blood lymphocyte subsets of early breast cancer patients and of men with stage I seminoma of the testis were studied up to 6 years after radiotherapy. Similar results were obtained in the two patient groups. After a temporary decrease, the CD4-w29 or "memory" T cells recovered completely, while the CD4-45R or "naive" T cells remained decreased up to 6 years after irradiation. The number of CD8 T lymphocytes did not change during or after treatment. Because of the decrease of a subset of CD4 cells, and the unchanged values of CD8 cells, the CD4/CD8 ratio decreased significantly after irradiation, and remained lower than before treatment up to 5-6 years after radiotherapy. The number of both HLA-DR positive CD4 and HLA-DR positive CD8 T cells ("activated" T cells) increased significantly after irradiation. The natural killer (NK) cells were not affected by treatment. We propose that the recovery of the CD4 cells is limited to the CD4-w29 ("memory") population because of thymic dysfunction in older humans. The impact of the observed immune modulation on the low susceptibility for infections after local irradiation, and on putative antitumour immune responses is discussed.