Chat with AIExam 2: Innate Immunity: the Immediate Response to Infection
Although activation of the three different pathways of complement involves different components, the three pathways converge on a common enzymatic reaction referred to as complement fixation.
A. Describe this reaction.
B. Describe the enzyme responsible for this reaction in the alternative pathway.
C. Identify the three effector mechanisms of complement that are enabled by this common pathway.
(29) 
VerifiedA. The cleavage of C3 into C3a and C3b and the covalent bonding of C3b to the pathogen surface is called complement fixation, and is the reaction on which the alternative, lectin, and classical pathways of complement activation converge.
B. The enzyme responsible for cleaving C3 into C3a and C3b is called C3 convertase, and it differs in composition depending on the particular complement pathway. The classical and lectin pathways use the classical C3 convertase (C4b2a), whereas the alternative pathway uses the alternative convertase (C3bBb).
C. C3 is the most abundant complement component in the plasma and circulates as a zymogen, an inactive enzyme. When cleaved into C3a and C3b, three different effector mechanisms are armed: (1) C3b binds to and tags pathogens for destruction by phagocytes through binding to a C3b receptor, CR1; (2) C3b contributes to a multicomponent enzyme, C5 convertase, that catalyzes the assembly of the terminal complement components and the formation of the membrane-attack complex; and (3) C3a is an inflammatory mediator that serves as a chemoattractant and recruits inflammatory cells to the infection site.
pathways use the classical C3 convertase (C4b2a),whereas the alternative pathway uses the alternative convertase (C3bBb). C.C3 is the most abundant complement component in the plasma and circulates as a zymogen,an inactive enzyme.When cleaved into C3a and C3b,three different effector mechanisms are armed: (1)C3b binds to and tags pathogens for destruction by phagocytes through binding to a C3b receptor,CR1; (2)C3b contributes to a multicomponent enzyme,C5 convertase,that catalyzes the assembly of the terminal complement components and the formation of the membrane-attack complex; and (3)C3a is an inflammatory mediator that serves as a chemoattractant and recruits inflammatory cells to the infection site.
_____ are soluble complement fragments that mediate localized and systemic inflammatory responses.
(35) VerifiedC
The importance of CD59 (also known as protectin)is to _____.
(34) VerifiedB
the early stages of the alternative pathway of complement activation there are complement control proteins that are soluble (factors H and I)and associated with the cell surface (DAF and MCP).Identify the (i)soluble and (ii)cell surface-associated complement control proteins that operate in the terminal stages of the alternative pathway of complement activation,and describe their activities.
(37) Which of the following does not accurately describe complement components?
(32) Which of the following does not contain a glycosylphosphatidylinositol (GPI)lipid tail?
(27) Explain how the anaphylatoxins C3a and C5a contribute physiologically to inflammation during complement activation.
(31) Which of the following does not describe the actions of the coagulation system?
(38) Which of the following polymerizes to form a transmembrane channel that compromises the integrity of cell membranes?
(34) The membrane-bound proteins on human cells that dissociate and inactivate alternative C3 convertase to avoid complement activation are _____.
(32) Damage to tissues triggers a cascade of plasma proteins involving bradykinin and is known as _____.
(32) Explain why a genetic deficiency of C3 leads to a type of immunodeficiency characterized by recurrent and severe infections.
(36) Which of the three complement pathways becomes activated soonest after an initial infection?
(41) A.Review the differences between the three pathways of complement (alternative, lectin, and classical) in terms of how they are activated.
B.Distinguish which pathway(s) are considered part of an adaptive immune response and which are considered part of innate immunity, and say why.
(37) Which of the following is the membrane-bound form of C3 convertase of the alternative pathway of complement activation?
(35) Explain the similarities between membrane cofactor protein,factor H,and complement receptor 1 in terms of their complement control properties.
(44) All of the following statements are correct regarding \alpha2-macroglobulin except _____.
(34) ligand for CR3 and CR4 formed by the cleavage of C3b by the combined action of factors H and I is called _____.
(36) Explain how the alternative C3 convertase on pathogen cell surfaces is (A)formed and (B)stabilized.
(33) 
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