Podcast
Questions and Answers
What is the suffix given to the smaller fragment when a complement component is cleaved?
What is the suffix given to the smaller fragment when a complement component is cleaved?
Which of the following complement pathways involves the formation of C3 convertase?
Which of the following complement pathways involves the formation of C3 convertase?
What biological function is primarily associated with the protein C5a?
What biological function is primarily associated with the protein C5a?
Which component is key for the opsonization of pathogens?
Which component is key for the opsonization of pathogens?
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In the context of the complement system, which component is usually the largest fragment generated upon cleavage?
In the context of the complement system, which component is usually the largest fragment generated upon cleavage?
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Which pathway of complement activation is specifically triggered by antigen-antibody complexes?
Which pathway of complement activation is specifically triggered by antigen-antibody complexes?
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What initiates the alternative pathway of complement activation?
What initiates the alternative pathway of complement activation?
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Which of the following proteins is involved in the lectin binding pathway of complement activation?
Which of the following proteins is involved in the lectin binding pathway of complement activation?
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What role does the complement system serve in relation to the immune system?
What role does the complement system serve in relation to the immune system?
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Which immunoglobulin types can activate the classical pathway of complement?
Which immunoglobulin types can activate the classical pathway of complement?
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Study Notes
Complement System
- Consists of ~30 proteins in human serum
- Complements or assists other immune components
- Three pathways for activation: classical, alternative, lectin
Classical Pathway
- Activated by antigen-antibody complexes
- Requires IgG or IgM antibodies
- Specific antibody to antigen is required
Alternative Pathway
- Activated by microbial cell surface substances
- Bacterial polysaccharides, lipopolysaccharides
- Part of innate immunity
Lectin Pathway
- Activated when mannose-binding lectin (MBL) binds to carbohydrates on pathogens
- Part of innate immunity
Complement Activation Mechanisms
- Sequential proteolytic cleavage of complement proteins
- Creates effector molecules for eliminating microbes
- Activated complements become attached to microbial surfaces
Complement System Functions
- Cell lysis: Membrane attack complex (MAC) insertion into cell membranes, leading to cell lysis
- Opsonization: C3b binds to microbes, increasing phagocytosis
- Inflammation: C3a, C4a, and C5a trigger chemotaxis (attracting phagocytes) and mast cell degranulation
- Antibody production enhancement: C3b derivatives enhance B-lymphocyte antibody production
Major Histocompatibility Complex (MHC)
- Collection of highly polymorphic genes on chromosome 6
- Two major classes: I and II
- Also called Human Leucocytic Antigens (HLA)
MHC Class I
- Glycoproteins expressed on all nucleated cells
- Presents antigen to cytotoxic T cells (CD8)
- MHC restriction is required for recognition
MHC Class II
- Glycoproteins expressed on antigen-presenting cells (APCs)
- Presents antigen to helper T cells (CD4)
- MHC restriction necessary for recognition
MHC Importance
- Organ transplantation: Compatibility between donor and recipient MHC genes is crucial
- Disease association: Specific MHC antigens are associated with certain diseases
Cytokines
- Glycoproteins involved in cell signaling during immune responses
- Mode of action: secreted by cells, bind to receptors, trigger intracellular signaling
- Classifications: interleukins (ILs), colony-stimulating factors (CSFs), tumor necrosis factors (TNFs), interferons (IFNs), chemokines
Cytokine Functions
- Proinflammatory cytokines (IL-1, IL-6, TNF-α): Effects include fever, leukocyte production, acute phase protein production, septic shock
- Interferons (IFNs): Antiviral activity, immunomodulatory effects
- Chemokines: Direct immune cell migration to inflamed area
Clinical Uses of Cytokines
- Antiviral (e.g., treatment of viral hepatitis)
- Antitumor
- Anti-autoimmune (e.g., Crohn's disease treatment)
- Boosting leukocytes (preventing infections after cancer treatment)
Side Effects of Cytokines
- Systemic symptoms (e.g., fever, malaise)
- Cytokine storm (overproduction of inflammatory cytokines)
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Description
Explore the essential functions and pathways of the complement system in human immunity. This quiz covers the classical, alternative, and lectin pathways, as well as mechanisms of complement activation and their roles in immune responses. Test your knowledge on how these pathways assist in pathogen elimination.
