【2017年整理】免疫生物学作业0110 - 副本.docVIP

Recognition of bacteria by mannose-binding lectin can lead to their destruction by the same mechanisms as recognition by antibody. Explain why this is so, and describe additional common features between these pathways of pathogen recognition 答：（1）无论是甘露糖凝集素途径还是经典途径，都需要经过一系列的反应使病原体表面结合大量的C3b分子，通过C3b分子发挥进一步的功能。由于作用的中间体相同，所以两条途径最终破坏细菌的机制以相同。 在细胞表面聚集C3b发挥作用之后的途径都是完全相同的；而在这一步骤之前，两条途径也有很多相似之处：经典途径第一个被活化的蛋白C1q和甘露糖凝集素与丝氨酸蛋白酶形成的复合物类似，都是由六个相同的球状头部和胶原状尾部组成的六聚体；经典途径和甘露糖凝集素途径都在病原体表面形成C4b和C2a组成的C3转化酶。 The innate immune system uses two different strategies to identify pathogens: recognition of nonself and recognition of self. (a) Give examples of each and discuss how each example contributes to the ability of the organism to protect itself from infection. (b) What are the disadvantages of these different strategies? 答：（1）识别非我：C反应蛋白，五聚体，一种与特定细菌或真菌细胞壁脂多糖的磷脂酰胆碱部分结合的识别分子。 识别自我：NK细胞上有识别自我的受体，该受体与自身细胞结合产生抑制信号抑制NK细胞的活性，使NK细胞不杀死自身细胞。 这些不同的机制的缺点是：（1）识别非我的分子突变，则会导致不能够有效的识别病原体，造成免疫系统的缺陷。识别自我的分子突变，则会导致自身免疫性疾病，免疫系统将可能攻击自身。（2）抗原应答具有局限性，限制了识别非我的分子的作用范围。（3）交叉反应性，识别非我的分子有可能会识别具有与外来抗原表位相似的结构自我分子，导致免疫系统攻击自身；识别自我的分子有可能会识别具有与自身配体相似的非我分子，从而忽略抗原。 3. Mutation produced during affinity maturation are initially generated randomly by the action of AID, and yet eventually amino acid changes to the antibody are clustered to the three CDRs in the V regions. (a) What is the relationship between the location of the CDRs and the V(D)J junctions? (b) How might randomly generated mutations in DNA lead to an enrichment of mutations that are restricted to the CDRs after an immune response? 整个V区均与分布有突变的碱基（虽然存在着一些突变热点）。发生在FR区的氨基酸序列的突变，回导致抗体基本结构的破坏，因而这种突变将不会被选择，而发生在CDR区域的突变有可能增强抗原结合性，所以突变可能被选择，因而免疫应答后ＤＮＡ随机产生的突变将会富集在ＣＤＲ区域。 4.MHC class Ⅰ and class Ⅱ molecules are structurally and functionally homologous, yet have dissimilar pathways of assembly and delivery to the cell surface. (a) Describe how these differences in assembly and delivery are integrated with the different functions of class Ⅰ and class Ⅱ molecules. (b) H