How We Immune Disease-人体如何免疫疾病（1）

How We Become Immune to Disease
The body has a special way of handling infection. It has a system that fends off the first traces of an infectious substance and then, through a “memory,” gives the body a long-lasting immunity against future attacks by the same kind of invader.
Many substances could harm the body if they ever entered it. These substances, or antigens, range from bacteria and pollen to a transplanted organ (viewed by the body as an invader). To fight them the body makes special chemicals knows as antibodies.
Antibodies are a class of proteins called immunoglobulins. Each antibody is made of a heavy chain of chemical subunits, or amino acids, and a light chain of them. The light chain has special sites where the amino acids can link with their complements on the antigen molecule. When an antibody hooks up with an antigen, it often puts the antigen out of action by inactivating or covering a key potion of the harmful substance. In some cases, through the process of opsonization, antibodies “butter” the surface of some antigens and make them “tastier” to phagocytes, which engulf the antigens. Sometimes an antibody hooks up to bacteria antigen but needs an intermediate, or complement, to actually destroy the bacterium. As the antibody-antigen complex circulates in the blood, the complex “fixes” complement to it. In turn, the complement causes powerful enzymes to eat through the bacterial cell wall and make the organism burst.
immune 免疫的
fend off 挡开
immunity 免疫力
antigen 抗原
pollen 花粉
transplant 移植
antibody 抗体
immunoglobulin 免疫球蛋白
subunit 亚单位
amino acid 氨基酸
complement 补体
inactivate 使不活泼
opsonization 调理素作用
phagocyte 吞噬作用
engulf 吞没
Complex复合物
Eat through 腐蚀穿
burst 爆裂