裂变中子照射对小鼠胸腺淋巴细胞亚群的影响Ⅰ.胸腺淋巴细胞亚群对裂变中子的辐射敏感性

The effects of fission neutron irradiation on lymphocytic subgroups in murine thymus I. The radiosensitivity of thymic lymphocytic subgroups to fission neutron radiation

小鼠经梯度剂量的裂变中子和６０Ｃｏγ射线照射后１ｄ，其胸腺细胞数和胸腺重量指数的变化，都显示了对中子和γ射线有辐射敏感和辐射抗性两种成分的存在，而同一种成分对中子辐射的敏感性又高于对γ射线的辐射敏感性。对中子辐射敏感成分的Ｄ０值依次为０．６４和０．３４Ｇｙ，对γ射线的Ｄ０值则相应为０．８３和０．８７Ｇｙ。ＲＢＥ值分别为１．３０和２．５６。照射后小鼠胸腺Ｔ细胞亚群的变化表明，两种Ｔ细胞亚群的辐射敏感性也是非均质性的，粗略评价，对中子和γ射线的辐射敏感性均是Ｌｙｔ＋２细胞高于Ｌ３Ｔ４＋细胞，而两类细胞对中子的辐射敏感性又均高于对γ射线的辐射敏感性，经计算各类细胞对中子照射的Ｄ３７值，Ｌ３Ｔ４＋细胞为６．１４Ｇｙ，Ｌｙｔ＋２细胞为３．２８Ｇｙ；对γ射线则分别为１１．３８和１０．４２Ｇｙ，由此得到的ＲＢＥ值分别为１．８５和３．１８。

C 57 BL/6J Mice aged 6-8 weeks were exposed to graded doses of whole body irradiation with either fission neutrons or 60 Co γ rays respectively. The changes in thymic cellularity and weight index on the 1st day post irradiation demonstrated that the lymphocytes of the thymus consisted of two components, i.e., radiosensitive and radioresistant ones to neutrons or γ rays. The same component showed higher radiosensitivity to neutrons than to γ rays. D 0 Value of the radiosensitive component of thymocytes and that of weight index of thymus to neutron irradiation were 0.64 and 0.34 Gy, respectively, while those to γ irradiation were 0.83 and 0.87 Gy. So RBE values were 1.30 and 2.56 respectively. The changes of thymic T lymphocytic subgroups after irradiation indicated that the radiosensitivity of Lyt + 2 cells and L 3T 4 + cells was also non homogeneous. The radiosensitivity of Lyt + 2 cells not only to neutrons but also to γ rays was higher than that of L 3T 4 + cells. The radiosensitivity of both subgroups to neutrons was higher than that to γ rays. The calculated D 37 values of neutron irradiated two subgroups were 6.14 Gy (L 3T 4 + cells) and 3.28 Gy (Lyt + 2 cells) respectively, while those of γ irradiated two subgroups were 11.38 (L 3T 4 + cells) and 10.42 Gy (Lyt + 2 cells). Thus, RBE values were 1.85 and 3.18, respectively.