Rao P E, Sussdorf D H
Immunology. 1978 Dec;35(6):907-15.
In a microcytotoxicity assay composed of pooled, urethane-induced lung adenoma cells from BALB/c mice and syngeneic lymphocytes sensitized to these tumour cells, the addition of serum either from adenoma-bearing or normal BALB/c mice resulted in a depression of the cytotoxic response. This suppressive factor was stable to heating at 56° for 30 min and was unaffected by freezing and thawing. Pre-treatment of tumour targets with serum prior to the addition of lymphocytes was not protective, but pretreatment of sensitized lymphocytes with serum inhibited their cytotoxic ability to the same extent as did treatment of the whole culture with serum. Suppressive activity could be removed from serum by absorption with sensitized, but not with unsensitized lymphocytes. While sera from syngeneic or adenoma-bearing nude mice were free of suppressive activity, the activity appeared in nude animals following thymus implantation. When whole BALB/c serum was fractionated on a Sephadex G-200 column, suppressive activity equivalent to that found in the whole serum was observed consistently in fractions eluting in the region of 14,000 dalton proteins. No activity could be found in this region when sera lacking suppressive ability were separated. Sodium dodecyl sulphate—polyacrylamide gel electrophoresis (SDS-PAGE) of Sephadex fractions representing the activity zone revealed a protein with a molecular weight of 14,000 daltons which was present in fractions from active sera, but absent from fractions of inactive sera. SDS-PAGE of Sephadex fractions without suppressive activity, i.e. not representing the activity zone, did not produce this band. Both the activity zone in the Sephadex profile and the SDS-PAGE band could be demonstrated with sera from thymus-restored nude mice. Our observations indicate the existence of a low-molecular weight protein in the circulation of normal BALB/c mice which is capable of suppression of cell-mediated anti-tumour cytotoxicity. The presence of this factor appears to be thymus-dependent, and it seems to exert its effect by binding to sensitized killer lymphocytes.
在一种微细胞毒性试验中，该试验由来自BALB/c小鼠的经氨基甲酸乙酯诱导的肺腺癌细胞集落以及对这些肿瘤细胞致敏的同基因淋巴细胞组成，添加来自荷腺瘤或正常BALB/c小鼠的血清会导致细胞毒性反应受到抑制。这种抑制因子在56℃加热30分钟后仍保持稳定，并且不受冻融的影响。在添加淋巴细胞之前用血清预处理肿瘤靶细胞没有保护作用，但用血清预处理致敏淋巴细胞会抑制其细胞毒性能力，其程度与用血清处理整个培养物相同。抑制活性可以通过用致敏淋巴细胞吸收从血清中去除，但不能用未致敏淋巴细胞吸收。虽然来自同基因或荷腺瘤裸鼠的血清没有抑制活性，但在植入胸腺后，裸鼠体内出现了这种活性。当在Sephadex G - 200柱上对整个BALB/c血清进行分级分离时，在洗脱分子量约为14,000道尔顿蛋白质区域的级分中始终观察到与全血清中相当的抑制活性。当分离缺乏抑制能力的血清时，在该区域未发现活性。对代表活性区的Sephadex级分进行十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳（SDS - PAGE）显示，活性血清级分中存在一种分子量为14,000道尔顿的蛋白质，而无活性血清级分中不存在。对不具有抑制活性的Sephadex级分（即不代表活性区）进行SDS - PAGE未产生此条带。来自胸腺恢复的裸鼠的血清也能显示出Sephadex图谱中的活性区和SDS - PAGE条带。我们的观察结果表明，正常BALB/c小鼠循环中存在一种低分子量蛋白质，它能够抑制细胞介导的抗肿瘤细胞毒性。这种因子的存在似乎依赖于胸腺，并且它似乎通过与致敏杀伤淋巴细胞结合来发挥作用。
