The Effects of X-irradiationin Vitroon Subpopulations of Human Lymphocytes

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Abstract
Human peripheral blood lymphocytes isolated using a Ficoll-Uropolinum gradient were exposed to 1-25 Gy [gray] X-rays and were cultured for up to 72 h. Before irradiation and after 2, 24, 48 and 72 h the total numbers of surviving cells per ml of culture and the frequencies of cells spontaneously forming rosettes (E) and active rosettes (AE) with sheep red blood cells, cells bearing receptor for activated complement (EAC) and cells spontaneously forming rosettes with mouse red blood cells (ME) were determined. Irrespective of the duration of in vitro culture, the radiosensitivity of the subpopulations of human lymphocytes increased in the order E < EAC = ME < AE rosette forming cells. The frequencies of surviving cells, null with respect to the surface markers (E and EAC), was calculated. Disappearance of rosette-forming cells under the influence of radiation was largely due to the shedding of their receptors and not exclusively to cell death. The extreme radiosensitivity of the subpopulation of T lymphocytes capable of AE rosette formation, may possess diagnostic significance in persons accidentally exposed to radiation.