[Severe damage of CD4-2H4+ T subpopulation cells (naive T cells and suppressor/inducer) by radiation therapy, their recovery being promoted by a plant alkaloid].

Radiation therapy eventually causes severe damage of lymphocytes. We examined numbers of CD4+ (helper/inducer) and CD8+ (cytotoxic/suppressor) T cells, as well as CD4-2H4+ and CD8-2H4+ subpopulation cells in the peripheral blood of patients during the radiation therapy, when lymphocytes decreased to the lowest level (500-1000/mm3). The highest molecular isoforms of the CD45 antigen family, recognized by monoclonal antibody (2H4), are designated CD45RA. Mature but antigen non-primed, naive T cells expressing CD45RA were assumed to be most radiosensitive among T cells, from the view point of radiation biology. Analysis of their damage was, therefore, the focus of this study. The mean values for all cell populations were significantly reduced as compared to those of normal individuals, the CD4-2H4+ cells having been affected most severely. Recovery was first detected in CD8-2H4+ cells after one month. Intravenous injections of a plant alkaloid, Cepharanthin, was effective in promoting recovery of CD4-2H4+ subpopulation.