T lymphocyte subpopulations in blood following radiation therapy for breast cancer.

T helper and T suppressor lymphocyte subpopulations were examined before and after postoperative adjuvant radiation therapy for breast cancer. Absolute numbers of all T cell subsets were reduced by 70-80%. The proportion of IgG-Fc receptor-bearing T cells (Tg cells) was significantly reduced and that of IgM-Fc receptor-bearing T cells (Tm cells) significantly increased at completion of local radiation therapy with 45 Gy (4500 rad). Proportions of T suppressor (Ts) and T helper (Th) cells determined by monoclonal antibodies were not changed by radiation therapy. The overlapping between Tg and Ts subpopulations was 20-30% as examined by double labelling.