Lymphocyte subpopulation of human peripheral blood responds to the low doses of ionizing radiation,interleukin-2 and to both factors

Increasing of 3H-thymidine incorporation in lymphocytes of human peripheral blood which depends non-linearly on X-ray dose (3 cGy max) and interleukin-2 (IL-2) concentration (17.5 Units/ml) is shown. However addition of IL-2 (17.5 U/ml) into the medium of cells after irradiation (3 cGy) decreases almost to the control the effects induced by independently shown actions. Lymphocytes subpopulation responsible for the described phenomena are isolated during the fractionation of lymphocytes in the density gradient and pH (V-fraction BSA). Cell fraction less than 1-2% from the isolated lymphocytes is characterized by increasing of spontaneous corporation of 3H-thymidine, large sizes (d > 8 mkm), decreasing repair after UV-irradiation. It is believed that low dose irradiation and IL-2 activate this cell subpopulation of "last reaction", and higher doses of these factors and this both actions stopping 3H-thymidine incorporation initiate apoptosis. The relation of this sell subpopulation and before proposed ontogenetical reserve cells is discussed.