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Ch. 16 - Innate Immunity: Nonspecific Defenses of the Host
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398당신이 사용하는 게 아니라요?교과서 변경
12장, 문제 6

A decrease in the production of C3 would result in
a. increased susceptibility to infection.
b. increased numbers of white blood cells.
c. increased phagocytosis.
d. activation of C5 through C9.
e. none of the above

검증된 단계별 안내
1
Understand the role of C3 in the complement system, which is a part of the innate immune response. C3 is central to the activation of the complement cascade, leading to opsonization, inflammation, and formation of the membrane attack complex.
Recall that C3 cleavage produces C3a and C3b. C3b acts as an opsonin, enhancing phagocytosis by marking pathogens for destruction, while C3a contributes to inflammation.
Consider what happens if there is a decrease in C3 production: fewer C3b molecules will be available to opsonize pathogens, leading to reduced phagocytosis.
Recognize that reduced C3 also means less activation of downstream components like C5 through C9, which form the membrane attack complex responsible for lysing pathogens.
Conclude that a decrease in C3 would impair the immune response, making the host more susceptible to infections, which corresponds to option (a) increased susceptibility to infection.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Complement System and C3 Protein

The complement system is a part of the innate immune response that enhances the ability to clear pathogens. C3 is a central protein in this system, playing a key role in opsonization, inflammation, and activation of downstream components. A decrease in C3 impairs these functions, reducing immune efficiency.
추천 영상:
가이드 코스
04:16
Proteins of the Complement System

Role of C3 in Phagocytosis

C3b, a fragment of C3, binds to pathogens and marks them for destruction by phagocytes, a process called opsonization. Reduced C3 levels lead to less opsonization, thereby decreasing phagocytosis and weakening pathogen clearance.
추천 영상:
가이드 코스
08:57
Steps of Phagocytosis

Activation Cascade of Complement Components C5-C9

Activation of C3 is necessary to trigger the later stages of the complement cascade, including the formation of the membrane attack complex (C5-C9) that lyses pathogens. Without sufficient C3, this cascade is not effectively initiated, impairing pathogen destruction.
추천 영상:
가이드 코스
03:42
3) Classical Pathway