Immunology Quiz on Antibodies and Immune Response

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Questions and Answers

What is the primary function of antibodies during the first response to a microbe?

To block harmful effects of microbes and toxins (correct)

To produce large amounts of IgE antibodies

To enhance the activity of natural killer cells

To activate the complement system immediately

Which class of immunoglobulin is primarily involved in foetal protection by maternal antibodies?

IgA

IgG (correct)

IgM

IgD

What mechanism do antibodies mainly use to activate effector functions?

Complement activation

Binding to natural killer cells

Fc regions (correct)

Fab regions

In addition to IgG, which other class of immunoglobulin is involved in blocking toxins?

IgA Signup and view all the answers

Which of the following statements accurately describes the secondary response of antibodies?

It generates antibodies more rapidly and in larger amounts. Signup and view all the answers

What is the first step in the process of phagocytosis?

Binding of the microbe to phagocytic cells Signup and view all the answers

Which receptor enhances phagocytosis by binding to antibody-coated antigens?

FcγR Signup and view all the answers

Which cells are primarily responsible for antibody-dependent cellular cytotoxicity (ADCC)?

Natural killer cells Signup and view all the answers

What type of infections is ADCC particularly important for?

Enveloped virus infections Signup and view all the answers

Which of the following enhances phagocytosis significantly?

Antibody coasting of the microbe Signup and view all the answers

What do natural killer (NK) cells release to kill opsonized cells?

Granule proteins Signup and view all the answers

Which receptor on NK cells is specifically for mediating ADCC?

CD16 Signup and view all the answers

Which of these immune responses is NOT associated with phagocytosis?

Release of chemical messengers Signup and view all the answers

Which receptor do eosinophils utilize to recognize helminthic parasites?

FcεRI Signup and view all the answers

What role does IL-5 play in the immune response against helminths?

It enhances eosinophil activation. Signup and view all the answers

What happens when eosinophils bind to helminths?

Eosinophils trigger a release of toxic granules. Signup and view all the answers

Which type of antibodies are primarily involved in activating mast cells during allergic reactions?

IgE antibodies Signup and view all the answers

How do eosinophils damage helminths once they recognize and bind to them?

By releasing harmful proteins from granules. Signup and view all the answers

What triggers the production of IgE antibodies in response to helminthic parasites?

The release of IL-4 by Th2 cells. Signup and view all the answers

What is the main function of mast cells during an allergic reaction?

To release histamine and cytokines. Signup and view all the answers

In which type of immune response are eosinophils primarily involved?

Helminthic infections. Signup and view all the answers

What is the primary role of antibodies in the context of microbial infections?

To block the binding of microbes and toxins to host cells Signup and view all the answers

Which toxin is produced by the bacterium Clostridium tetani?

Tetani toxin Signup and view all the answers

What is meant by the term 'neutralization of microbes'?

The blocking of microbial adhesion to host cells Signup and view all the answers

Which of the following can produce rigid paralysis in skeletal muscles?

Tetani toxin Signup and view all the answers

What is the function of immunoglobulins or antibodies known as antitoxins?

To neutralize bacterial toxins Signup and view all the answers

Why is adhesion considered the first step in microbial infection?

It allows specific binding of microbes to host cell surfaces Signup and view all the answers

What type of organism is Leishmania?

Parasite Signup and view all the answers

What serious condition can tetani toxin lead to?

Death due to paralysis Signup and view all the answers

What role do complement components C3a and C5a play in the immune response?

They attract neutrophils to the infection site. Signup and view all the answers

Which pathway is initiated by the binding of an antibody to a microbe?

Classical pathway Signup and view all the answers

What occurs during the activation of C1 in the classical pathway?

C1 cleaves C4 and C2 into their respective fragments. Signup and view all the answers

Which component is primarily responsible for initiating the formation of the Membrane Attack Complex?

C5b Signup and view all the answers

How does the lectin pathway differ from the classical pathway?

It does not involve antibody binding. Signup and view all the answers

What is the role of C3 convertase in complement activation?

It cleaves C3 into active components C3a and C3b. Signup and view all the answers

What is the role of C3 convertase in the lectin pathway of complement activation?

It cleaves C3 into C3a and C3b. Signup and view all the answers

What is generated when C5 convertase cleaves C5?

C5a, which promotes inflammation, and C5b, which initiates MAC formation. Signup and view all the answers

Which of the following statements is true regarding the activation of C5?

C5a promotes inflammation by attracting immune cells. Signup and view all the answers

Which complement component binds to the surface of the microbe during the classical and lectin pathways?

C4b Signup and view all the answers

What is the final outcome of the formation of the Membrane Attack Complex (MAC)?

It leads to the disruption of microbial cell membranes. Signup and view all the answers

How does C3b contribute to the amplification of the complement pathway?

By forming complexes that cleave additional C3. Signup and view all the answers

What triggers the spontaneous activation of C3 in the lectin pathway?

Hydrolysis occurring in the bloodstream. Signup and view all the answers

Study Notes

Humoral Immune Response II

Humoral immune response involves antibodies
Antibodies are produced in the primary response to a microbe
Antibodies are produced in larger amounts in secondary responses
Antibodies use Fab regions to bind and block harmful microbes and toxins
Antibodies use Fc regions to activate diverse effector mechanisms
There are 5 classes of immunoglobulins (IgG, IgA, IgM, IgE, and IgD)

Antibody Structure

Antibodies have two identical heavy chains and two identical light chains linked by disulfide bonds
The variable region (Fab) of the antibody binds to antigens
The constant region (Fc) of the antibody activates effector functions

Antibody Classification

IgG, has subclasses : IgG1, IgG2, IgG3, IgG4.
IgM - pentameric structure
IgA - dimeric structure
IgE - monomeric structure
IgD - monomeric structure

Antibody Effector Functions

Neutralization: Antibodies block microbes and toxins from binding to host cells
Opsonization: Antibodies coat microbes, making them more readily recognized and ingested by phagocytes
Complement activation: Antibodies activate complement leading to cytolysis of microbes
Antibody-dependent cell-mediated cytotoxicity (ADCC): Antibodies bind to target cells, enabling NK cells to kill the target cells.
Neonatal immunity: Maternal antibodies cross the placenta and provide protection to the newborn.
Feedback inhibition of B cell activation: Prevents overproduction of specific antibodies

Functions of Immunoglobulins

Antibody specificity
Antibody biologic activity : neutralization, opsonization, antibody dependent cellular cytotoxicity (ADCC), complement activation

1- Neutralization Of Microbes & Microbial Toxins

Antibodies block microbes penetration, preventing infection
Antibodies block toxins binding to cellular receptors
Antibodies prevent microbes/toxins from attaching to host cells.

2- Opsonization And Phagocytosis

Antibodies coat microbes, facilitating phagocytosis by macrophages and neutrophils
Opsonin is a molecule that enhances phagocytosis (IgG, C3b)
The Fc region of IgG binds to receptors on phagocytes

3- Antibody dependent cellular cytotoxicity (ADCC)

NK cells and other leukocytes bind to antibody-coated cells
NK cells express Fc receptors (FcyRIIIA)
Activated NK cells release granule proteins to kill the opsonized cell

4- Ig E and Eosinophil/ Mast Cell-Mediated Reactions

IgE antibodies activate mast cells and eosinophils
These reactions are important in defense against parasites and allergies
Eosinophils and mast cells secrete granules that contain toxic proteins for helminths

5- Complement Activation

Complement Activation involves a series of proteins that assist or complement the activity of antibodies in destroying microbes
Involves sequential proteolytic cleavage
Three major pathways of activation: classical, alternative and lectin pathways

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Description

Test your knowledge on the primary functions of antibodies, their classes, and mechanisms in immune responses. This quiz covers topics ranging from phagocytosis to antibody-dependent cellular cytotoxicity (ADCC). Dive deep into the fascinating world of immunology and understand how our immune system protects us from infections.