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免疫系统与癌有关系似乎是无庸置疑的了,但为什么免疫系统不能控制肿瘤的生长仍是一大问题。在对肿瘤产生免疫性的经典的动物实验中,先让接种的肿瘤暂时地生长,发生的免疫反应好象不能攻击已经形成的初期小结节,但能攻击在初期病变完全切除后而接种的肿瘤。这也许是因为首次移植时造成的局部组织损伤,在血管长入肿瘤小结节时消失了。此时已经、发展起来的免疫反应不能发觉在自身毛细血管屏蔽后面的恶性细胞。对此现象的通常解释是:免疫系统初次同肿瘤相遇,其抵抗力尚未提高,抗原过多或封闭因子征服了免疫系统。但在某些动物系统中能够证明,初次接种物的生长是“加强”的,而第二次同样的肿瘤接种物将如同第二次移植反应那样地被破坏。肿瘤消退甚至在能测出封闭因子后还能发生。无论怎样,在自发的恶性肿瘤的早期,免疫系统所以保持不活动不能用“封闭”现
There seems no doubt that the immune system is related to cancer, but why the immune system can not control the growth of tumors is still a big issue. In a classical animal experiment that is immune to tumors, the inoculated tumor is allowed to grow temporarily, and the immune response that appears to fail to attack the initial small nodules that have formed may attack the inoculated Tumor. This may be due to local tissue damage caused by the first transplant, which disappears as the blood vessels grow into small nodules of the tumor. At this point, the immune response developed can not detect the malignant cells behind the capillaries themselves. The usual explanation for this phenomenon is: the immune system first encounter with the tumor, its resistance has not increased, excessive antigen or blocking factor conquered the immune system. In some animal systems, however, it can be demonstrated that the growth of the primary inoculum is “boosted,” while the second secondary inoculum of the same will be destroyed as the second transplant. Tumor regression can occur even after the closure factor can be detected. In any case, in the early stage of spontaneous malignancy, the immune system can not be kept “inactive”