首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
The immune system is equal in complexity to the combined intricacies of the brain and nervous system. The success of the immune
The immune system is equal in complexity to the combined intricacies of the brain and nervous system. The success of the immune
admin
2018-04-17
47
问题
The immune system is equal in complexity to the combined intricacies of the brain and nervous system. The success of the immune system in defending the body relies on a dynamic regulatory communications network consisting of millions and millions of cells. Organized into sets and subsets, these cells pass information back and forth like clouds of bees swarming around a hive. The result is a sensitive system of checks and balances that produces an immune response that is prompt, appropriate, effective, and self-limiting.
At the heart of the immune system is the ability to distinguish between self and non-self. When immune defenders encounter cells or organisms carrying foreign or non-self molecules, the immune troops move quickly to eliminate the intruders. Virtually every body cell carries distinctive molecules that identify it as self. The body’s immune defenses do not normally attack tissues that carry a self-marker. Rather, immune cells and other body cells coexist peaceably in a state known as self-tolerance. When a normally functioning immune system attacks a non-self molecule, the system has the ability to remember the specifics of the foreign body. Upon subsequent encounters with the same species of molecules, the immune system reacts accordingly. With the possible exception of antibodies passed during lactation, this so-called immune system memory is not inherited. Despite the occurrence of a virus in your family, your immune system must learn from experience with the many millions of distinctive non-self molecules in the sea of microbes in which we live. Learning entails producing the appropriate molecules and cells to match up with and counteract each non-self invader.
Any substance capable of triggering an immune response is called an antigen. Antigens are not to be confused with allergens, which are most often harmless substances ( such as ragweed pollen or cat hair) that provoke the immune system to set off the inappropriate and harmful response known as allergy. An antigen can be a virus, a bacterium, a fungus, a parasite, or even a portion or product of one of these organisms. Tissues or cells from another individual ( except an identical twin, whose cells carry identical selfmarkers) also act as antigens; because the immune system recognizes transplanted tissues as foreign, it rejects them. The body will even reject nourishing proteins unless they are first broken down by the digestive system into their primary, non-antigenic building blocks. An antigen announces its foreignness by means of intricate and characteristic shapes called epitopes, which protrude from its surface. Most antigens, even the simplest microbes, carry several different kinds of epitopes on their surface; some may even carry several hundred. Some epitopes will be more effective than others at stimulating an immune response. Only in abnormal situations does the immune system wrongly identify self as non-self and execute a misdirected immune attack. The result can be a so-called autoimmune disease such as rheumatoid arthritis or systemic lupus erythematosis. The painful side effects of these diseases are caused by a person’s immune system actually attacking itself.
How do the cells in the immune system recognize an antigen as foreign or non-self?
选项
A、Through an allergic response.
B、Through blood type.
C、Through fine hairs protruding from the antigen surface.
D、Through characteristic shapes on the antigen surface.
答案
D
解析
细节题。根据题干可以定位到最后一段。该段第六句大意为,一个抗原的异质性是通过一种错综的和特有的形态被证实的,这种形态叫做抗原决定基。因此可以判断正确答案是[D]。
转载请注明原文地址:https://kaotiyun.com/show/60BZ777K
0
考研英语一
相关试题推荐
Aslongaspeoplehavelookedupatthenightsky,theyhavewonderedwhetherhumanityisaloneintheuniverse.Ofplacesclose
WithJapan’swelfaresystembucklingunderthedemandsofanageingsociety,theworld’soldestmanapologizedyesterdayforhis
Successfulsportsprofessionalscanearnagreatdealmoremoneythanpeopleinotherimportantprofessions.Somepeoplethinki
【F1】Themajorityofsuccessfulseniormanagersdonotcloselyfollowtheclassicalrationalmodeloffirstclarifyinggoals,ass
Thetechnologicalrevolutionsofthelasttwodecadeshaveplacedasevereburdenontheconceptoftechnologytransfer.Itisq
Thetechnologicalrevolutionsofthelasttwodecadeshaveplacedasevereburdenontheconceptoftechnologytransfer.Itisq
【F1】AnydiscussionoftheAmericaneducationalsystemwouldbelessthancompleteifitdidnotmentiontheemphasisthatmanyc
Relativitytheoryhashadaprofoundinfluenceonourpictureofmatterbyforcingustomodifyourconceptofaparticleinan
随机试题
从气候变迁的角度讲,南宋中期到元代中期,我国气候进入()
铸造金属全冠面应均匀磨除()
下列关于对列报前期影响数不切实可行的表述,正确的有()。
________是指学习者为了提高学习的效果和效率,有目的、有意识地制定的有关学习过程的复杂的方案。
妄想是一种病理性的歪曲信念,是病态的推理和判断,它具有以下特征:(1)信念的内容与事实不符,没有客观现实基础,但患者坚信不疑;(2)妄想内容均涉及患者本人,总是与个人的利害有关;(3)妄想具有个人独特性;(4)妄想的内容因文化背景和个人经历而有差异
若有定义语句:inta[2][3],*p[3];,则以下语句中正确的是()。
ThemainreadersofmedicaljournalsareWhichofthefollowingstatementsisNOTtrue?
Thefirehascausedgreatlosses,butthefactorytriedto______theconsequencesbysayingthatthedamagewasnotasseriousas
Overhalftheworld’speoplenowliveincities.Thelatestreport"GlobalReportonHumanSettlements"saysthe(36)______change
InonlytwodecadesAsianAmericanshavebecomethefastest-growingU.S.minority.Astheirchildrenbeganmovingupthroughthe
最新回复
(
0
)