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　　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 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.

　　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 of non-self molecules, the immune troops move quickly to eliminate the invaders. 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, the 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 molecule, 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 necessitates producing the appropriate molecules and cells to match up with and counteract each non-self invader.

　　Any substance capable of stimulating an immune response is called an antigen. Tissues or cells from another individual (except an identical twin, whose cells carry identical selfmarkers) 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 epitomes, which stick out from its surface. Most antigens, even the simplest microbes, carry several different kinds of epitomes on their surface, some may even carry several hundred. Some epitomes 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 so-called autoimmune disease. The painful side effects of those diseases are caused by a person’s immune system actually attacking itself. (427 words)

　　1. We know from the passage that the immune system _______________

　　[A] is no less complicated than the nervous system.

　　[B] far exceeds the human brain in intricacy.

　　[C] is enclosed by numerous sensitive cells.

　　[D] results in an effective communications network.

　　2. The principal task of the immune system is to _______________

　　[A] recognize and eliminate all foreign molecules that enter the body.

　　[B] remove all the substances that invade the body organisms.

　　[C] defend the body from the attacks of different viruses and bacteria.

　　[D] identify and specify all nonself molecules it encounters.

　　3. The remembering power of a person’s immune system is _______________

　　[A] mostly descended from his/her ancestors.

　　[B] partially passed down from his/her mother.

　　[C] mainly acquired through fighting against foreign cells.

　　[D] basically generated by its communications network.

　　4. Which of the following is NOT true according to the passage?

　　[A] A tissue transplanted from father to daughter would be less acceptable than that transplanted between twins.

　　[B] The immune system would never wrongly identify self as nonself and execute a misdirected immune attack.

　　[C] When a normally functioning immune system attacks a nonself molecule, the system will remember the specifics of the foreign body.

　　[D] The immune cells and other body cells can coexist peaceably in a state known as selftolerance.

　　5. The main idea of the passage may be generalized as_______________

　　[A] the success of the immune system in distinguishing foreign substances.

　　[B] the normal and abnormal activities of the immune system in the body.

　　[C] the unfavorable effects of the immune system on organ transplantation.

　　[D] the essential duties of the immune system in guarding the body.

　　核心词汇

　　intricacy n. 错综复杂的事物;纷繁难懂之处

　　dynamic a. 动态的,有动力的,有力的

　　back and forth来回地,反复地

　　hive n. 蜂房,蜂箱

　　organism n. 生物体,有机体

　　molecule n.分子

　　tissue n. (动、植物的)组织;薄的纱织品

　　antigen n. 抗原

　　epitome n. 摘要,缩影,化身

　　microbe n. 微生物,细菌

　　难句剖析

　　1. The result is a sensitive system of checks and balances that produces an immune response that is prompt, appropriate, effective and self-limiting.

　　【解析】 句子的主干是The result is a sensitive system of checks and balances。that引导定语从句。

　　【译文】 这就创造了一个灵敏的检测和平衡系统，它可以快速、及时、有效和自我限制的产生免疫响应。

　　2. 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 necessitates producing the appropriate molecules and cells to match up with and counteract each non-self invader.

　　【解析】 本句子的主干是your immune system must learn from experience…。Despite 引导让步状语，with引导的短语作状语，in which引导定语从句，learning引导后置定语，主语是your immune system，match up 和谐，相配。

　　【译文】 尽管病毒可能来自家族，但是人的免疫系统必须从实践中学习如何在人类所生活的充满微生物的世界里去分解那些大量异己，并创造出相应的分子或者细胞来对付它们。

　　3. Only in abnormal situations does the immune system wrongly identify self as non-self and execute a misdirected immune attack.

　　【解析】 这是一个倒装句，only位于句首修饰状语，强调in abnormal situations。identify…as 把……认为……。

　　【译文】 只有在不正常的情况下，免疫系统才会错把自我当成异己并执行错误的进攻。

　　文章类型： 科普类——人体免疫细胞

　　本文主要介绍了免疫系统保护人体的功能，并对免疫系统的复杂性和抗原做了说明。当免疫细胞遇到携带外来的分子或者异己分子的细胞或者组织时，会进行攻击和消灭它们。

　　试题解析

　　1. 从文中可知，免疫系统_______________

　　[A] 不亚于神经系统复杂。

　　[B] 远比人脑复杂。

　　[C] 被无数敏感细胞包围。

　　[D] 是一个有效的通讯网络。

　　细节事实题【正确答案】[B]

　　原文对应信息是第一段第一句The immune system is equal in complexity to the combined intricacies of the brain and nervous system.(免疫系统的复杂性等于大脑与神经系统的复杂性之总和。)

　　2. 免疫系统的主要任务是_______________

　　[A] 识别、消灭侵入体内的异己细胞。

　　[B] 移除入侵体内的所有物质。

　　[C] 保护身体免受不同病毒和细菌的攻击。

　　[D] 识别和认定它碰到的所有细胞。

　　细节事实题【正确答案】[A]

　　原文对应信息是第二段第一、二句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 of nonself molecules, the immune troops move quickly to eliminate the invaders.(免疫系统的核心是自我与异己的识别能力。当免疫细胞遇到携带外来分子或异己分子的细胞或组织时，这些免疫细胞会行动迅速，消灭那些入侵者。)

　　3. 一个人的免疫细胞记忆能力是_______________

　　[A] 大多数继承了她或他的祖先。

　　[B] 部分遗传于他或她的妈妈。

　　[C] 主要通过与外部细胞斗争获得。

　　[D] 基本通过它的通讯网络产生。

　　细节事实题【正确答案】[C]

　　原文对应信息是第二段最后一句your immune system must learn from experience with the many millions of distinctive nonself molecules…and cells to match up with and counteract each nonself invader.(但是人的免疫系统必须从实践中学习如何在人类所生活的充满微生物的世界里去分解那些大量异己，并创造出相应的分子或者细胞来对付它们。)可知，它的记忆能力是通过与外部细胞斗争而得到的。

　　4. 根据所给材料,下面哪种说法是错误的?

　　[A] 动植物组织在父女之间的移植没有双胞胎之间的移植容易接纳。

　　[B] 免疫系统不会错把自我当成异己并执行错误的进攻。

　　[C] 一个正常运转的免疫系统在攻击一个异己分子时，可以记忆这个异己分子的全部细节。

　　[D] 人体的免疫细胞和其他体细胞能够在一种叫做自体耐受性的状态下和平共处。

　　细节事实题【正确答案】[B]

　　原文对应信息是第三段最后一句Only in abnormal situations does the immune system wrongly identify self as nonself and execute a misdirected immune attack.(只有在不正常的情况下，免疫系统才会错把自我当成异己并执行错误的进攻。)而其他三项文中都有提到，故可排除。

　　5. 本文主要讲的是_______________

　　[A] 免疫细胞成功的区分外部物质。

　　[B] 体内免疫细胞的正常和非正常的活动。

　　[C] 器官移植方面免疫细胞的不利影响。

　　[D] 免疫细胞保护身体的基本责任。

　　中心主旨题【正确答案】[D]

　　第一段讲免疫系统复杂性，第二段着重介绍了免疫系统的任务、识别能力、记忆能力，并排斥来自其他组织或细胞，总体来看主要讲的是免疫细胞保护身体的功能。

　　全文精译

　　免疫系统的复杂性相当于大脑和神经系统的复杂性之和。免疫系统之所以能成功的保卫身体就在于它拥有一个由数百万个细胞组成的可动态调整的通信网。这些细胞组成人体的各种组织，然后像蜂群围绕蜂巢一样来回往复的传递信息，这就创造了一个灵敏的检测和平衡系统，它可以快速、及时、有效和自我限制的产生免疫响应。

　　免疫系统的核心是自我与异己的识别能力。当免疫细胞遇到携带外来分子或异己分子的细胞或组织时，这些免疫细胞会行动迅速，消灭那些入侵者。事实上，每一个人的体细胞都有自己独特的分子，视为自我。人体的免疫细胞通常是不攻击那些带有自我标记的组织的。并且人体的免疫细胞和其他体细胞是可以在一种叫做自体耐受性的状态下和平共处的。一个正常运转的免疫系统在攻击一个异己分子时，可以记忆这个异己分子的全部细节。以后再遇到同种异己分子时，免疫系统就可以有针对性的做出反应。由于在哺乳期可能会出现抗体的例外情况，因此这种所谓的免疫系统的记忆能力不是通过遗传得到的。尽管病毒可能来自家族，但是人的免疫系统必须从实践中学习如何在人类所生活的充满微生物的世界里去分解那些大量异己，并创造出相应的分子或者细胞来对付它们。

　　任何能引起免疫反应的物质都被称为抗原。任何来自其他个体的组织或细胞都是抗原，同源双胞胎除外，因为他们带有同源标记。由于免疫系统把移植过来的组织和细胞视为异己，因此总是排斥它们。如果营养蛋白不首先被消化系统分解成原始的非抗原性的高分子链节，身体甚至也将会拒绝这些营养蛋白。抗原的表面有一种突起，从这种突起不同的复杂外形就可以分辨出是否为外来异己。大多数抗原，即使是最简单的微生物，在其表面也会带有很多种不同的这类突起，有的甚至有上百种。这些突起更容易引起免疫反应。只有在不正常的情况下，免疫系统才会错把自我当成异己并执行错误的进攻。

　　这就是一种被称为自体免疫的疾病。这种病的痛楚在于这是人类免疫系统的自我攻击。

　　第一段：免疫系统的复杂性。

　　第二段：免疫系统的识别能力。

　　第三段：免疫系统排斥任何来自其他个体的组织或细胞。

　　第四段：给出全篇文章的结论。