大多数实验诱发的动物肿瘤及许多人类肿瘤表现出肿瘤相关抗原,针对这些抗原机体产生一定的免疫反应。虽然这些免疫反应存在,而且,患瘤动物的淋巴细胞在体外也能够破坏瘤细胞,但是,肿瘤细胞在体内还是能够生长。为什么能够对瘤细胞发生反应的动物不能排斥肿瘤?许多不同的机制可以 Most experimental animal tumors and many human tumors exhibit tumor-associated antigens that produce some immune response against these antigens. Although these immune responses exist and the tumor-bearing animal lymphocytes can destroy the tumor cells in vitro, the tumor cells can still grow in vivo. Why can animals that react to tumor cells not reject tumors? Many different mechanisms can