Microbial Infection and Immune Response Quiz

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Questions and Answers

What is the first step of infection?

Invasion of host cells

Adhesion of microbes (correct)

Destruction of host tissues

Replication of microbes

What do antibodies do in relation to microbial infection?

Prevent binding of microbes to host cells (correct)

Increase microbial virulence

Stimulate tissue damage

Enhance microbial adhesion

Which of the following best describes neutralization of toxins?

Enhancing the effects of the toxins

Stimulating immune response to toxins

Preventing toxins from binding to receptors (correct)

Allowing toxins to enter cells

What type of toxin is produced by Clostridium tetani?

Neurotoxin Signup and view all the answers

What is the role of antitoxins?

Neutralize the effects of toxins Signup and view all the answers

Leishmania is characterized as which type of organism?

Parasite Signup and view all the answers

What is one consequence of the tetani neurotoxin?

Skeletal muscle rigidity Signup and view all the answers

What does the term 'host specificity' refer to?

The types of tissues a microbe can infect Signup and view all the answers

What is the first step in the process of phagocytosis?

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

Which receptor enhances phagocytosis by binding to IgG antibodies?

FcγR Signup and view all the answers

What is the first step of infection by Leishmania in host cells?

Adhesion to the cell Signup and view all the answers

What type of cells are involved in antibody-dependent cellular cytotoxicity (ADCC)?

Natural killer cells Signup and view all the answers

How do antibodies affect the toxicity of certain microorganisms?

They block receptor binding of the toxin Signup and view all the answers

Which mechanism is primarily responsible for targeting cells infected with enveloped viruses?

Antibody-dependent cellular cytotoxicity Signup and view all the answers

What role do macrophages play in the immune response?

Engulfing and destroying pathogens Signup and view all the answers

What is opsonization?

Enhanced phagocytosis of microbes Signup and view all the answers

Which antibody is primarily involved in opsonization?

IgG Signup and view all the answers

What is the function of the FcγRIIIA receptor on natural killer cells?

Activating the NK cell for cytotoxicity Signup and view all the answers

How do microbial surface antigens enhance phagocytosis?

They promote binding with antibodies Signup and view all the answers

What does the term 'neutralization' refer to in the context of toxicity?

The prevention of toxin binding Signup and view all the answers

What role does C3b play in phagocytosis?

It enhances phagocyte binding to microbes Signup and view all the answers

Which cells are primarily responsible for recognizing and destroying antibody-coated cells?

Natural killer cells Signup and view all the answers

Which Fc region specifically binds to the high-affinity receptor for IgG?

FcγRI (CD64) Signup and view all the answers

What is activated by the antigen-antibody complex in the classical pathway?

C3b production Signup and view all the answers

What role do eosinophils play in combating helminthic parasites?

They release toxic substances stored in their granules. Signup and view all the answers

How do eosinophils recognize helminthic parasites?

By binding to IgE antibodies on the parasite. Signup and view all the answers

Which cytokine is primarily involved in eosinophil activation against helminths?

IL-5 Signup and view all the answers

What is the function of mast cells in the immune response to helminths?

They secrete cytokines to attract more leukocytes. Signup and view all the answers

What happens when eosinophils bind to helminths via IgE?

Eosinophils release granules containing toxic proteins. Signup and view all the answers

What is the role of Th2 cells in the immune response against helminths?

They secrete IL-5 to activate eosinophils. Signup and view all the answers

What substance do eosinophils release during their response to helminths?

Major basic protein (MBP) and cationic eosinophilic protein. Signup and view all the answers

What kind of immune reaction do IgE antibodies mediate?

Mast cell and eosinophil-mediated reactions. Signup and view all the answers

What do C3a and C5a complement byproducts primarily lead to?

Increased inflammation and neutrophils Signup and view all the answers

Which function of immunoglobulins involves blocking microbes and toxins?

Neutralization Signup and view all the answers

How do antibodies facilitate phagocytosis?

By coating microbes to make them recognizable Signup and view all the answers

What is the role of the Membrane Attack Complex (MAC)?

To create pores in microbes for lysis Signup and view all the answers

What does Antibody-dependent cellular cytotoxicity (ADCC) do?

Signals NK cells to kill infected cells Signup and view all the answers

Which of the following is NOT a function of immunoglobulins?

Histamine release Signup and view all the answers

Which statement about eosinophils is correct?

They play a role in helminthic infections. Signup and view all the answers

The byproducts of complement activation lead to an increase in?

Neutrophils at the infection site Signup and view all the answers

What is the primary role of complement components C3a and C5a during inflammation?

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

Which pathway of complement activation is initiated by the binding of C1 to an antibody?

Classical pathway Signup and view all the answers

What is the result of the formation of the C3 convertase in the classical pathway?

C3 is cleaved into C3a and C3b. Signup and view all the answers

How is the C5 convertase formed in the classical pathway?

C3b combines with the C3 convertase. Signup and view all the answers

What initiates the lectin pathway of complement activation?

Mannose-binding lectin binding to sugar molecules. Signup and view all the answers

What is the fate of C5 after it is cleaved by C5 convertase?

It triggers inflammation via C5a and the MAC formation via C5b. Signup and view all the answers

What is a key feature of the complement proteins before activation?

They exist in an inactive form. Signup and view all the answers

Which component binds first in the classical pathway of complement activation?

C1 Signup and view all the answers

Study Notes

Humoral Immune Response II

Humoral immune response involves antibodies, produced in response to microbes and toxins
Antibodies are produced during primary responses, increasing in secondary responses for increased effectiveness
Antibodies use Fab regions to bind and block harmful microbes/toxins, whilst Fc regions activate effector mechanisms for elimination
Five classes of immunoglobulins (IgG, IgA, IgM, IgE, and IgD) exist
Antibody structure features include variable and constant regions on heavy and light chains, with disulfide bonds
Antibody classification includes various structures, each with distinct functions
IgG has subtypes (IgG1-4), IgA is primarily a dimer, IgM is a pentamer, and IgE is a monomer
Specific serum concentrations and half-lives for each antibody type are shown in table format, along with related information on secreted forms and functions.

Antibody Effector Functions

IgG neutralizes microbes and toxins, opsonizes antigens for phagocytosis, and activates complement pathways
IgG facilitates antibody-dependent cellular cytotoxicity (ADCC), neonatal immunity, and B-cell feedback
IgM activates classical complement pathway and mucosal immunity
IgA primarily functions in mucosal immunity, neutralizing microbes and toxins in mucosal tissues
IgE primarily facilitates eosinophil and mast cell reactions against helminths, playing a role in allergic responses

Antibody-Dependent Cellular Cytotoxicity (ADCC)

ADCC involves NK cells binding to antibody-coated cells and destroying them
NK cells express the FcyRIIIA receptor and are important for ADCC
Activated NK cells release granule proteins to kill opsonized cells

IgE and Eosinophil/Mast Cell-Mediated Reactions

IgE antibodies activate mast cells and eosinophils, playing a role in allergic diseases and helminth defense
Eosinophils release granule contents, and mast cells secrete cytokines, attracting more leukocytes to destroy helminths
IL-5, produced by Th2 cells, enhances eosinophils for helminth killing

Complement Activation

Complement proteins are a collection of molecules that play roles in host defense, antibody-mediated tissue injury, and help assist Ig to destroy microbes
Complement exists in an inactive form; activation involves sequential proteolytic cleavages
Three major pathways for complement activation include classical, alternative, and lectin
The classical pathway is antibody-dependent
The alternative pathway is initiated by spontaneous hydrolysis of C3
The lectin pathway is activated when mannose-binding lectin (MBL) binds to specific sugar molecules on microbes

Functions of Immunoglobulins

Antibodies exhibit two key characteristics: specificity and biological activity
Immunoglobulins (Igs) perform various functions, including neutralization, opsonization, ADCC, and complement activation.

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Description

Test your knowledge on the fundamentals of microbial infection and the immune response. This quiz covers key concepts such as the role of antibodies, neutralization of toxins, and specifics about pathogens like Clostridium tetani. Perfect for students looking to reinforce their understanding of microbiology and immunology.