免疫力_綜合百科-飛外

免疫力(immunity)

抵抗入侵微生物或較大寄生蟲攻擊或克服感染的能力。以身體的免疫系統(tǒng)的正常運(yùn)作為基礎(chǔ)，在自然免疫或天生免疫中，出生時(shí)就有的免疫機(jī)制對(duì)眾多不同的微生物發(fā)生作用，不管先前是否遭遇過。後天的免疫反應(yīng)（適應(yīng)後對(duì)特定微生物或其產(chǎn)物發(fā)生作用）受到先前該種微生物出現(xiàn)的刺激。先前受到特定病原體感染或接種疫苗時(shí)，會(huì)產(chǎn)生這類的免疫。天生免疫的機(jī)制包括物理障礙（如皮膚）和化學(xué)障礙（例如唾液中出現(xiàn)的殺菌）。穿透身體自然障礙的微生物會(huì)遭遇到抑制其生長與繁殖的物質(zhì)（例如干擾素）。噬細(xì)胞（吞噬粒子的細(xì)胞）包圍并摧毀入侵的微生物，而自然殺手細(xì)胞會(huì)刺穿微生物的細(xì)胞膜。天生免疫并不賦予身體永久的抵抗力或免疫力。後天免疫以B細(xì)胞和T細(xì)胞對(duì)於抗原的辨識(shí)為基礎(chǔ)，在天生機(jī)制不足以遏止抗體進(jìn)一步入侵時(shí)活躍起來。殺手T細(xì)胞或毒害T細(xì)胞摧毀受感染的細(xì)胞和外來的細(xì)胞。助手T細(xì)胞把受抗體出現(xiàn)而遭到刺激并增殖的B細(xì)胞變?yōu)榉置诳贵w的細(xì)胞，也就是漿細(xì)胞。漿細(xì)胞所產(chǎn)生的抗體附著於產(chǎn)生抗體的細(xì)胞，標(biāo)示毀滅的記號(hào)。後天免疫仰賴致敏記憶B細(xì)胞和T細(xì)胞的長期存活，它們能在同一病原體再度感染時(shí)快速繁殖。亦請參閱immunodeficiency、immunology、leukocyte、reticuloendothelial system。

English version：

immunity

Ability to resist attack or overcome infection by invading microbes or larger parasites. Immunity is based on the proper functioning of the body's immune system. In natural or innate immunity, immune mechanisms present at birth work against a wide variety of microbes whether or not they have been encountered before. Acquired immune responses, tailored to act against a specific microbe or its products, are stimulated by the prior presence of that microbe. Previous infection with a particular pathogen, as well as vaccines, produce this type of immunity. The mechanisms of innate immunity include physical barriers (including the skin) and chemical barriers (such as bactericidal enzymes present in saliva). Microbes that penetrate the body's natural barriers encounter substances (such as interferon) that inhibit their growth or reproduction. Phagocytes (particle-engulfing cells), surround and destroy invading microbes, and natural killer cells pierce the microbe's outer membrane. Innate immunity does not confer lasting resistance, or immunity, to the body. Acquired immunity is based on the recognition of antigen by B and T cells and is activated when innate mechanisms are insufficient to stem further invasion by pathogens. Killer or cytotoxic T cells destroy infected and foreign cells. Helper T cells induce B cells stimulated by the presence of antigen to proliferate into antibody-secreting cells, or plasma cells. Antibodies produced by plasma cells bind to antigen-bearing cells, marking them for destruction. Acquired immunity relies on the long-term survival of sensitized T and B memory cells, which can proliferate quickly upon reinfection by the same pathogen. See also immunodeficiency, immunology, leukocyte, reticuloendothelial system.