原发免疫应和继发免疫反应.doc

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1、Bodydefence1Primaryimmuneresponseandsecondaryimmuneresponse原發免疫反應和繼發免疫反應Primaryimmuneresponse原發免疫反應：Itistheresponsethatisevokedwhenanantigenenteredintothebodyforthefirsttime.Afewdaysaftertheinvasionoftheantigens(eg.bacteria),thenumberofT-cellsgreatlyincreasestocombattheantigen.Thecell-mediate

2、dimmuneresponseisbeingtriggered,butisshortlived.它是病原體初次進入身體所引發的免疫反應，抗原(細菌)入侵身體後數天，T-細胞會增加以對抗抗原，細胞免疫反應被激發，但此種反應很短暫。Secondaryimmuneresponse繼發免疫反應：Thememorycellsproducedintheprimaryimmuneresponsewillremaininthecirculationforalongtime.Iftheantigeninvadesagain,thenumberofT-cellswillincreaserapidly

3、.Theresponseislongerlasting,morerapidandeffective,producinggreateramountsofTcells.Thisisduetothepresenceofmemorycellswhichcanrememberthepathogen.Thisresponseiscalledthesecondaryresponse.在原發免疫反應過後會有記憶細胞存於血中一段時期，當抗原再次入侵，可加快T-細胞及抗體的產生，免疫反應更強烈及更持久，這是因為記憶細胞可記住病原體，此種反應名為繼發免疫反應。Theimportanceofsecond

4、aryimmuneresponseindiseasesprevention:繼發免疫反應的重要性：Becauseoftheproductionofmemorycells,peoplecanbeimmunizedagainstcertaindiseasesuchaspolioandmeasles.因為記憶細胞可記住病原體，人類可在某些疾病獲得免疫力，例如小兒麻庳及麻疹。Thefunctionsofimmunesystem:免疫系統的功能：Thefunctionsoftheimmunesystemaretorecognize,respondtoandeliminateforeigns

5、ubstancesenteringthebodyorarisinginthebody.免疫系統可識別外物、對外物作出反應以致最終將它排除，阻止它們進入身體或在身體內出現。2Typesofimmunity免疫的種類Therearetwobasictypesofimmunity,passiveimmunityandactiveimmunity.免疫的種類基本有兩種：被動免疫和主動免疫1.Passiveimmunityisthepassingoftheantibodiesintoanindividualinsomewayratherthanbeingproducedbytheindiv

6、idualhimself,eg.antibodiescanpassacrosstheplacentafromamothertoherfoetus,orarepassedtothenewbornbodyinthemother’smilk.被動免疫是抗體非由個體自己產生，而是用某種方法輸入體內，例如透過胎盤將抗體從母體傳給胎兒，或透過母乳傳給初生嬰兒。Itmaybeacquiredartificiallybyinjectionofantibodiesfromotherindividual.eg.inthetreatmentoftetanusanddiphtheria.抗體亦可透過注射

7、而獲得，例如在預防白喉及破傷風時。Passiveimmunityistemporary.被動免疫只是短暫性的。2.Activeimmunityoccurswhenanorganismproducesitsownantibodies.主動免疫是指個體自己產生抗體。Itistheresultofaninfection.Oncethebodyhasstartedtoproduceantibodiesinresponsetoadiseasecausingagent,itmaycontin