Unit7 Immune Respon
Allergy or hypernsitivity is the result of an immune respon to a drug or preparation. As in any immune respon, the substance is recognized by the immune system as foreign. That is, the compound is en as antigenic. Once this occurs, a portion of the drug becomes questered into the lymphatics of the host, is procesd immunologically , and evokes the production of two types of effectors – specific antibodies will be produced against the antigen by B lymphocytes, and specifically nsitized effector cells ( T lymphocytes ) will be elaborated in large numbers. Both the B and the T lymphocytes are precommitted to the structure on the drug molecule with which they react. In the ca of a large complex molecule, as many drugs are, veral different structures may be recognized by different prcommitted T and B lymphocytes. The point is that as many different structures as possible are detected as foreign, and hence the respon is polyclonal. More that one precommitted precursor cell can respond to different parts of the molecule each capable of reaction with one small portion of the foreign molecule. That id, a normal immune respon has multiple specificities within it. That antigen, in turn, is a mosai
c of different substructures that give ri to spectrum of specificities. The word epitope has been coined to describe each individual structure that has been identified. The totality of the epitopes makes up the antigen.
所谓变应原或者超敏性，指的是机体对于某种药物或者制剂产生的免疫应答的结果。在任何免疫应答过程中，某种物质会被免疫系统当做是外来异质，这种复合物就是我们说的抗原。一旦这种情况发生，一部分药物经过免疫处理，被宿主的淋巴管隔离，促使生成两种效应物-B淋巴细胞生成特异性抗体以对抗抗原，特异性致敏效应细胞-T淋巴细胞大量产生。这两种淋巴对于与之反映的药物分子结构有前定向性，而如果是像许多药物那样的大的复合物分子的话，不同的前定向性B淋巴细胞和T淋巴细胞也能够识别当中的一些不同的结构。关键是，随着越来越多的不同结构被识别为外来异质，这种应答也势必变为多细胞特点。对于分子的不同部分，往往不止一种前定向性先质能够对其应答。实际情况是，它们各自负责能够与外来异质分子当中的一小部分发生反应。这就是说，正常的免疫应答其实有着多重特异性表现。所以相应的，抗原就是不同基础结构之上的镶嵌体，其引起一些列特异性的产生。鉴于此，学界创造出了“抗原决定基”这个词，用来描述每一个已经被确认的结构。所有抗原决定基的总和就是抗原。
During a normal immune respon, both humoral (antibody – mediated) and cellular immunity are evoked. This is also the ca with allergy. After exposures to the antigen (allergy), a period ensues during which an immune respon is being mounted but no symptoms appear (the lag period). After this, IgM antibodies begin to appear in the rum of individual. The are soon replaced by antibodies of the same specificity but of different chain structure. The cells producing producing antibodies undergo what is known as a switch from IgM to the other class of antibody: IgG, IgA, and IgE. It is the IgE that is involved in allergy for reasons that are described later. None of the other antibody class had been shown to be responsible for allergy.
在正常的免疫应答中，无论是体液（抗体调节）还是细胞免疫都可被激发。这也是变应性的实例。接触抗原（过敏原）之后，会出现一个免疫反应增加但无症状的阶段（迟缓反应期）。在这之后，免疫球蛋白M开始出现在免疫血清中，但是很快会被有相同抗原性但是具备不同链结构的抗体所替代，这些产生抗体的细胞会经历一个从免疫球蛋白M到其他种类抗体诸如免疫球蛋白G，免疫球蛋白A和免疫球蛋白E的转变过程。其中，免疫球蛋白E与变态反应有关，原因将在后面描述，除此之外，再也没有其他种类的抗体与变应性相关
了。
Molecules below a certain size are generally not recognized by the immune system as foreign. For example, proteins with molecular weights below approximately 10,000 do not evoke an immune respon. Yet many drugs are recognized as foreign even though their molecules are quite small. This phenomenon is due to what is known as the hapten effect. Many drugs have the capacity to bind to constituents of the blood. For example, penicillin, in some individuals, caus a distortion of the normal structure of albumin or the erythrocyte membrane, or both. The distorted albumin or membrane is now recognized by the recipient as foreign and no longer lf. During the immune respon that follows, the penicillin forms an epitope on the larger structure and antibodies are produced both to the penicillin and to the altered host component. The altered host component has become a carrier for the hapten penicillin. The important point here is that after antibody has once been formed, the carrier is not required for reaction of the antipenicilin antibodies with penicillin to occur.
一般来讲，当分子小于一定的大小的时候，是不会被免疫系统视为外来以质的。比如说。如果蛋白质的分子量小于10,000时，就不会引起免疫应答。然而为什么许多药物的分子已经很小，但仍然会被视作外来异质呢？究其原因，这一现象是由于所谓的半抗原效应引起的。许多药物都会和血液成分结合在一起，青霉素就是一个例子。在某些情况下，青霉素通过和血清蛋白或红细胞的结合，会引起正常蛋白结构或红细胞薄膜变形。这些变形的白蛋白和红细胞薄膜就会因此被接受者（受体）当做是外来异质（而受到攻击）了。在随后的免疫反应中，青霉素在较大分子结构上形成表位，对青霉素及以改变的宿主成分产生抗体。这种已改变的宿主成分则成为了半抗原青霉素的载体。最重要的一点是，一旦在抗体形成后，青霉素和反青霉素抗体之间的反应就不再需要载体的中介了。
Some drugs are antigenic by themlves. As might be expected, the are usually large molecule. In general, the more complex the molecule, the more readily it will evoke an immune respon. In addition, although any drug can be responsible for evoking allergy, some drugs have a much higher propensity to produce hypernsitivity than others. Drugs that are chemically reactive are more likely to nsitize a person than tho that are less reactive.
有些药物本身就是抗原，因为可以预见，药物当中总会有大分子的存在。而且一般来说，分子越复杂，越容易引发免疫应答。另外，尽管所有药物都有可能引发过敏的变应性反应，然而其中的一些则比其他的药物有着更高的倾向引起超敏反应。那些容易引起化学反应的有更高反应活性的药物也往往更有可能对人产生过敏症状。
11、抗生素的滥用
对于那些懂得抗生素选择耐药性的人来说，国际社会目前面临着一个主要公共健康危机是不令人惊讶的，自从第一个商业版本被提出，抗生素使用（和使用不当）已经猛增，现在包括了很多非医药的应用，1954年在美国2百万磅的抗生素被 生产，今天这个数字已经超过了5千万磅。
在美国，每年人类的治疗大约只有一半的抗生素是使用合理的，意思是在治疗细菌感染和被正确管理。
尤其是许多医生默认误导了要求用抗生素治疗感染和其他病毒感染的病人，这些疾病并不能由抗生素治愈。疾病控制与预防中心的研究者估计到每年有1亿5千万人开有抗生素的处
方但不住院的病人中有5千万是不需要的，在我主持的一个研究会，出席的医生超过80%承认一经要求就与了抗生素处方而没有更好的判断。
在工业化世界，大多数抗生素仅仅在处方下才能得到的，但是这种限制并没有确保合理应用，人们经常不能成功完成治疗的整个过程，然后病人大量贮备未用完剂量，并以低于治疗量的剂量来自己治疗、或者治疗他们的家人和朋友。在这两种情况下，不适宜的剂量将不能完全消除疾病病源，此外，也将促进耐药性菌株的生长，这些耐药菌株以后可能会产生难治性疾病。在发展中国家，抗生素使用所受控制更少，在工业化国家上市的许多同样的药物在柜台便可得到，不幸的是，当抗药性成为一个临床问题，那些没有能力去买昂贵药物的国家，可能没有可用的替代药物。
