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Immunology > Humoral immunity > Flashcards

Humoral immunity Flashcards

1
Q

What is the humoral immune system?

A

A component of the immune system that involves antibodies produced by B cells to fight infections

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2
Q

What are acute-phase proteins?

A

Plasma proteins produced by the liver during inflammation that mimic antibodies and aid in immune responses

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3
Q

What are some examples of acute-phase proteins?

A

C-reactive protein for opsonization and complement activation and haptoglobin for binding hemoglobin

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4
Q

What is the role of complement proteins?

A

They enhance immune responses by opsonizing pathogens promoting inflammation and forming the membrane attack complex MAC

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5
Q

What are the three pathways of complement activation?

A

The classical pathway the alternative pathway and the lectin-binding pathway

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6
Q

What triggers the classical pathway?

A

Binding of antibodies such as IgM or two IgG molecules to antigens on the pathogen surface

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7
Q

What triggers the alternative pathway?

A

Direct activation by microbial surfaces such as lipopolysaccharides LPS or aggregated IgA

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8
Q

What triggers the lectin-binding pathway?

A

Binding of mannose-binding lectin MBL to carbohydrate structures on the surface of pathogens

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9
Q

What are the main steps in the classical complement pathway?

A

C1 binds to antibodies followed by activation of C4 and C2 forming C3 convertase which cleaves C3 into C3a and C3b

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10
Q

What is the role of C3 convertase?

A

It cleaves C3 into C3a and C3b initiating amplification of the complement cascade

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11
Q

What happens to C3b after it is formed?

A

C3b binds to pathogen surfaces aiding in opsonization and forming C5 convertase

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12
Q

What is the role of C5 convertase?

A

It cleaves C5 into C5a a chemoattractant and C5b which initiates the formation of the membrane attack complex MAC

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13
Q

What is the membrane attack complex MAC?

A

A structure formed by C5b C6 C7 C8 and multiple C9 molecules that creates pores in the membrane of pathogens causing osmotic lysis

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14
Q

What is the role of C3a and C5a in the complement pathway?

A

They act as chemoattractants recruiting immune cells to the site of infection and enhancing inflammation

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15
Q

What is the difference between opsonization and lysis in the complement system?

A

Opsonization involves coating pathogens with C3b to enhance phagocytosis while lysis involves the destruction of pathogens via the MAC

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16
Q

What is the role of mannose-binding lectin MBL in the lectin pathway?

A

It binds to mannose residues on pathogen surfaces activating a cascade similar to the classical pathway

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17
Q

What is the role of C4 and C2 in the classical and lectin pathways?

A

C4 and C2 are cleaved to form C3 convertase which is central to complement activation

18
Q

What is the role of factor B in the alternative pathway?

A

Factor B binds to C3b on pathogen surfaces and is cleaved by factor D to form an alternative C3 convertase

19
Q

What is the role of factor D in the alternative pathway?

A

Factor D cleaves factor B when it is bound to C3b forming the C3 convertase in the alternative pathway

20
Q

What is the importance of complement regulation?

A

To prevent excessive activation and damage to host tissues

21
Q

What are some key complement regulators?

A

Complement inhibitors such as C1 inhibitor decay-accelerating factor DAF and CD59 protect host cells

22
Q

What is the role of C3b in opsonization?

A

C3b coats the pathogen surface making it easier for phagocytes to recognize and engulf the pathogen

23
Q

What is the role of complement in inflammation?

A

Complement components like C3a and C5a recruit immune cells and increase vascular permeability to enhance the immune response

24
Q

What is the role of C5b in the complement cascade?

A

C5b binds to C6 and C7 initiating the assembly of the MAC

25
Q

What are the terminal steps of the complement cascade?

A

C5b recruits C6 C7 C8 and multiple C9 molecules to form the MAC which creates pores in the pathogen membrane

26
Q

What is the significance of the complement system in humoral immunity?

A

It enhances the effectiveness of antibodies by promoting pathogen destruction opsonization and immune cell recruitment

27
Q

How does complement activation link the innate and adaptive immune systems?

A

Complement bridges innate and adaptive immunity by amplifying antibody responses and directly targeting pathogens for destruction

28
Q

What is the primary role of IgM in humoral immunity?

A

It is the first antibody produced in infections and is efficient at activating the complement system

29
Q

What is the primary role of IgG in humoral immunity?

A

It provides long-term immunity neutralizes pathogens and enhances phagocytosis

30
Q

What is the primary role of IgA in humoral immunity?

A

It protects mucosal surfaces by neutralizing pathogens and preventing their attachment

31
Q

What is the primary role of IgE in humoral immunity?

A

It mediates allergic responses and provides defense against parasites

32
Q

What are the outcomes of complement activation?

A

Pathogen lysis immune cell recruitment and enhanced phagocytosis

33
Q

What is antibody-dependent cellular cytotoxicity ADCC?

A

A process where antibodies recruit natural killer cells to destroy target cells

34
Q

How do IgM and IgG differ in complement activation?

A

IgM is more efficient in activating the complement system while IgG subclasses vary in their efficiency

35
Q

What is the importance of acute-phase proteins during infections?

A

They act as diagnostic markers of inflammation and enhance immune responses

36
Q

What is the role of antibodies in neutralization?

A

They block pathogens from binding to host cells and neutralize toxins

37
Q

What are the differences between the three complement pathways?

A

The classical pathway is antibody-dependent the alternative pathway is triggered by microbial surfaces and the lectin pathway is triggered by MBL binding

38
Q

What are the effector functions of antibodies in humoral immunity?

A

Neutralization opsonization complement activation and recruiting immune cells

39
Q

What is the order of the classical complement pathway?

A

1- Initiation: C1q binds to antigen-antibody complexes (e.g., IgM or IgG bound to antigens).
2- Activation of C1 Complex: C1r and C1s are activated, leading to cleavage of C4 into C4a and C4b.
3- Formation of C3 Convertase: C4b binds to the pathogen surface and combines with C2a, forming the C4b2a complex (C3 convertase).
4- C3 Activation: C3 convertase cleaves C3 into C3a (inflammatory mediator) and C3b (opsonin).
5- Formation of C5 Convertase: C3b joins C4b2a to form C5 convertase.
6- MAC Formation: C5 convertase cleaves C5 into C5a (chemoattractant) and C5b, initiating the assembly of the membrane attack complex (MAC).

40
Q

What is the order of the alternative complement pathway?

A

1- Spontaneous Hydrolysis of C3: C3 undergoes spontaneous hydrolysis to C3(H2O).
2- Formation of C3 Convertase: C3(H2O) binds factor B, which is cleaved by factor D to form the alternative C3 convertase (C3bBb).
3- Amplification Loop: C3 convertase generates additional C3b, which can further amplify complement activation.
4- Formation of C5 Convertase: Additional C3b binds to C3 convertase, forming the alternative C5 convertase.
5- MAC Formation: Similar to the classical pathway, C5b initiates the assembly of the MAC.

41
Q

What is the order of the lectin binding pathway?

A

1- Initiation: Mannose-binding lectin (MBL) binds to mannose residues on pathogens.
2- Activation of MASPs: MBL-associated serine proteases (MASPs) cleave C4 and C2, forming C3 convertase (C4b2a).
3- C3 Activation: Similar to the classical pathway, C3 convertase cleaves C3 into C3a and C3b.
4- Formation of C5 Convertase: C3b binds to C3 convertase, forming C5 convertase.
5- MAC Formation: C5b initiates the assembly of the MAC.

Immunology (25 decks)

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