MicroBio Chapter 15 Flashcards

Questions and Answers

What are the peptides presented by MHC class II peptide molecules?

Exogenous antigens (correct)

Endogenous antigens

Pathogen antigens

Cytotoxic antigens

In opsonization with IgG, why is it important that IgG react with the antigen before a phagocytic cell recognizes the antibody?

If the IgG is bound to the phagocyte before opsonization, it would be ingested by the phagocyte before it could bind to a pathogen.

Which class of antibody accounts for most of the circulating antibodies?

IgG

T-independent antigens can activate B cells directly.

True Signup and view all the answers

What is the function of the secretory component of the IgA molecule?

To protect IgA from being destroyed by proteolytic enzymes. Signup and view all the answers

Where are T cells and B cells produced?

Bone marrow Signup and view all the answers

What are cytotoxic T cells primarily responsible for?

Cell-mediated immunity Signup and view all the answers

What happens when a helper T cell is activated?

Two populations of cells are formed: memory Th cells and effector Th cells. Signup and view all the answers

Which of the following antibodies is a pentamer?

IgM Signup and view all the answers

How is a T cell receptor different from a B cell receptor?

T-cell receptors must have antigen broken down inside a cell and presented by an MHC molecule. Signup and view all the answers

Which of the following is not typical of an antigen?

Low molecular weight Signup and view all the answers

Each class of antibody is specifically defined by its:

Amino acid sequence of the constant region of the heavy chain. Signup and view all the answers

Which of the following do not induce a strong immune response?

Lipids and simple sugars Signup and view all the answers

The immunoglobulin monomer consists of:

Two heavy and two light chains. Signup and view all the answers

What are CD8 cells?

T cytotoxic cells. Signup and view all the answers

Please select the correct statement regarding MHC molecules.

Helper T cells recognize antigens presented on MHC class II molecules. Signup and view all the answers

Why would a person who has their tonsils removed be more susceptible to certain infections?

Tonsils are secondary lymphoid organs; they help react to microbes in the oral cavity. Signup and view all the answers

Class II MHC molecules are found primarily on:

Macrophages and dendritic cells. Signup and view all the answers

All antigens are immunogens.

False Signup and view all the answers

The only class of antibody that can cross the placenta is:

IgG Signup and view all the answers

The surface receptors on B and T cells both:

Have variable and constant regions. Signup and view all the answers

Which is the most efficient at initiating the classical pathway of the complement cascade?

IgM Signup and view all the answers

Only antigen-presenting cells produce MHC class II molecules.

True Signup and view all the answers

The immune response is directed against an entire molecule.

False Signup and view all the answers

The chains of an antibody molecule are bonded to one another by:

Disulfide bonds. Signup and view all the answers

According to clonal selection theory:

Each B cell is already programmed to produce a specific antibody. Signup and view all the answers

Proteins that react specifically with the chemical structures in the antigen that induced them are called:

Antibodies. Signup and view all the answers

Where do T cells mature?

Thymus. Signup and view all the answers

What are giant cells used for?

To contain bacterial infections. Signup and view all the answers

The immunoglobulin that is important in hypersensitivity reactions is:

IgE. Signup and view all the answers

Which is the first antibody class made during the primary response to an antigen?

IgM. Signup and view all the answers

Identify the roles of natural killer cells.

Antibody-dependent cellular cytotoxicity; negative selection of lymphocytes that recognize normal 'self' molecules; regulation and direction of certain immune responses. Signup and view all the answers

What is the definition of clonal selection?

The process in which a lymphocyte's antigen receptor binds to an antigen, allowing the lymphocyte to multiply. Signup and view all the answers

Which of the following is the most abundant immunological class produced?

IgA. Signup and view all the answers

How long after initiation of a primary response do significant amounts of antibody appear in the blood?

10-14 days. Signup and view all the answers

Ag-Ab binding may result in all of the following EXCEPT:

Fever. Signup and view all the answers

Perforin is produced by:

NK cells. Signup and view all the answers

Who received the Nobel Peace Prize in Medicine for his work on antibody therapy?

Von Behring. Signup and view all the answers

If a denatured antigen were analyzed, would it be expected to have the same epitopes as its native counterpart?

Yes and No; some epitopes are dependent on 3D conformation while others depend on the amino acid sequence. Signup and view all the answers

What is the term synonymous with antibody?

Immunoglobulin. Signup and view all the answers

The characteristic function and properties of each class of antibody are determined by the:

Constant region on the heavy chains. Signup and view all the answers

How is the central portion of a T cell receptor complex functionally analogous to the center of the B cell receptor complex?

Both receptors bind epitopes. Signup and view all the answers

Antibody and antigen are held to one another by covalent bonds.

False Signup and view all the answers

An IgG molecule has two:

Heavy chains, light chains and antigen binding sites. Signup and view all the answers

What do 'clonal selection' and 'clonal expansion' refer to?

All of the above. Signup and view all the answers

It would be useful if antigens were delivered directly to:

Peyer's patches and M cells. Signup and view all the answers

The cells that actually secrete antibodies are:

Plasma cells. Signup and view all the answers

What would be an appropriate response if an antigen is presented on MHC class II molecules?

An effector CD4 cell activates the presenting cell. Signup and view all the answers

Epitopes or antigenic determinants are:

Parts of an antigen recognized by an antibody. Signup and view all the answers

Each class of antibody is specifically defined by its:

Amino acid sequence of the constant region of the heavy chain. Signup and view all the answers

CD4 cells are also known as:

T helper cells. Signup and view all the answers

Which of the following does NOT form a memory population after activation and differentiation?

Macrophages. Signup and view all the answers

The variable region of an antibody occurs:

On all 4 chains. Signup and view all the answers

The immunoglobulin monomer consists of:

2 heavy and 2 light chains. Signup and view all the answers

A scientist isolated a new blood-borne virus that shuts down MHC presentation. Why was the warning about its destructibility questioned?

Other mechanisms, like NK cells and interferons, can clear viral infections. Signup and view all the answers

Which of the following antibodies is a dimer?

IgA. Signup and view all the answers

Please select the correct statement regarding MHC molecules.

Helper T cells recognize antigens presented on MHC class II molecules. Signup and view all the answers

Gene rearrangement is responsible for the generation of the various antibody molecules.

True Signup and view all the answers

Antigens interact with antibodies at:

The outer end of each arm of the Y. Signup and view all the answers

There are __________ classes of antibodies.

5 Signup and view all the answers

The Fc region on IgG:

Interacts with complement and attaches to receptors on macrophages. Signup and view all the answers

What do secondary lymphoid organs facilitate?

Interactions between cells. Signup and view all the answers

All antigens are immunogens.

False Signup and view all the answers

Microphages and dendritic cells are:

Antigen-presenting cells. Signup and view all the answers

Specific regions on an antigen molecule to which the immune response is directed are called:

Antigenic determinants. Signup and view all the answers

How is a T-cell receptor different from a B-cell receptor?

T-cell receptors must have antigen broken down inside a cell and presented by an MHC molecule. Signup and view all the answers

Which of the following are antigen-presenting cell(s)?

Macrophages, dendritic cells, and B cells. Signup and view all the answers

Study Notes

Antigen Presentation and Activation

Peptides presented by MHC class II molecules originate from exogenous antigens.
Helper T cells recognize antigens presented on MHC class II molecules, activating immune responses.
Activation of T helper cells results in memory Th cells and effector Th cells, which further activate B cells.

Antibody Classes and Functions

IgG is the most abundant class of circulating antibodies and can cross the placenta.
IgM is a pentamer and is the first antibody produced during primary immune response.
IgA is a dimer important in mucosal immunity.
IgE is involved in hypersensitivity reactions.

Immune Cell Production and Function

T cells and B cells are produced in the bone marrow; T cells mature in the thymus.
Cytotoxic T cells (CD8 cells) are responsible for cell-mediated immunity, targeting infected cells.
Plasma cells are the specific cells that secrete antibodies.
Natural killer (NK) cells play roles in antibody-dependent cellular cytotoxicity and negative selection of lymphocytes.

Antigen Properties and Immune Response

Not all antigens are strong immunogens; low molecular weight substances like lipids and simple sugars do not induce robust responses.
Antigens interact with antibodies at the outer ends of the antibody's Y-structure; these sites are known as epitopes or antigenic determinants.
Clonal selection occurs when a lymphocyte's antigen receptor binds to an antigen, prompting the cell to proliferate.

Cellular Immunology

Giant cells contain bacterial infections through a process of aggregation and encapsulation.
Monomeric antibodies consist of two heavy and two light chains linked by disulfide bonds.
CD4 cells (T helper cells) play a critical role in activating the immune response through helper functions.

Mechanisms of Action

Opsonization involves antibodies like IgG coating pathogens to enhance phagocytosis by phagocytes.
Complement activation can be initiated most effectively by IgM, leading to pathogen lysis.

Memory and Response Duration

Memory populations are formed by activated B cells and T cells, allowing for quicker responses upon re-exposure to antigens.
Significant antibody levels appear in the blood within 10-14 days following primary response initiation.

Antigen Prerequisites and Recognition

Antigen-presenting cells, including macrophages and dendritic cells, express MHC class II molecules and facilitate T-cell activation.
The FC region of IgG interacts with complement proteins and receptors on macrophages, promoting immune clearance.

Infants and Pathogen Defense

Removal of tonsils can increase susceptibility to respiratory infections due to loss of these secondary lymphoid organs which monitor oral cavity microbes.

Miscellaneous

Gene rearrangement allows for the diversity of antibody molecules.
Antigenic determinants are specific regions targeted by immune responses, and covalent bonds do not exist between antibodies and antigens.

Scientific Milestones

Emil von Behring received the Nobel Prize for his contributions to antibody therapy, demonstrating the medical importance of immunology.

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Description

Test your knowledge with these flashcards covering key concepts from Chapter 15 of Microbiology. This quiz focuses on important terminology and definitions related to immune responses and antigen presentation. Perfect for students looking to reinforce their understanding of microbiological principles.