我们每个人小时侯都种过牛痘和注射过卡介苗吧,它们可以为你预防天花和结核病。这种奇妙的防御和抵抗疾病的能力,医学上叫做“免疫”。你知道免疫作用是怎样形成的吗?应该说,直接从牛痘疱上取下来的疫苗,也是有毒性的。由于在生产过程中,经过多次繁殖,使毒性降得极低,以致在人体内不但不会引起疾病,相反会形成一种抵抗疾病的物质,叫做“抗体”。医学上把那些进入人体后能形成抗体的物质(如疫苗),叫做“抗原”。 Each of us has had vaccinia and injections of BCG for a few days. They can prevent smallpox and tuberculosis for you. This wonderful defense and ability to fight disease is medically called “immune.” Do you know how the immune system is formed? It should be said that vaccines taken directly from vaccinia are also toxic. Because in the production process, after repeated breeding, the toxicity is reduced so much that it will not only cause illness in the human body, but will instead form a kind of disease-resistant substance called “antibody”. Medically, substances (such as vaccines) that can form antibodies after entering the body are called “antigens.”