Human Anatomy and Physiology : Help with Antigens, Antibodies, and MHCs

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

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Example Question #1 : Help With Antigens, Antibodies, And Mh Cs

Which of the following attaches directly to pathogens to mark them for destruction?

Possible Answers:

T-cells

Macrophages

Antibodies

Plasma cells

B-cells

Correct answer:

Antibodies

Explanation:

Antibodies are produced by plasma cells (mature B-cells) with specific binding affinity for surface proteins that have been presented by antigen-presenting cells, like dendritic cells and macrophages. Once the plasma cell is stimulated by the presence of the specific antigen, it increases production of its antibody. These antibodies enter the blood and bind the antigen molecules on the surface of the pathogen cell. Cytotoxic T-cells and cytokines can then interact with the antibodies to initiate lysis of the infected cell or pathogen.

Example Question #2 : Help With Antigens, Antibodies, And Mh Cs

Which of the following statements is true?

Possible Answers:

B-lymphocytes have antibodies that attach to presented antigens

A B-lymphocyte will release different antibodies until one of them attaches to an antigen

Memory T-cells release antibodies in the event of infection by a previously encountered pathogen

An antibody can attach to multiple antigens

Correct answer:

B-lymphocytes have antibodies that attach to presented antigens

Explanation:

It helps to think of antigens and antibodies like a lock and key: they are highly specific for one another. B-lymphocytes create only one type of antibody. When this antibody attaches to an antigen presented by a macrophage or antigen-presenting cell, the B-lymphocyte will differentiate with the help of a helper T-cell. The result is replication of the B-lymphocyte to produce more of the same antibody from plasma cells and generate memory B-cells to easily respond in the event of a second infection by the pathogen.

Example Question #3 : Help With Antigens, Antibodies, And Mh Cs

The human immune system is organized along two broad arms: innate immunity and adaptive immunity. The differences between these two approaches to immunity are not always black and white, but can be described in general terms with regard to immunological memory. Adaptive immunity displays this type of memory, and mounts a more intense response to pathogens upon second and subsequent exposures.

Within adaptive immunity, the system is further divided into humoral immunity and cell-mediated immunity. We can say that antibodies are the primary mediators of the former, while CD8 T-cell based cytotoxicity is the mediator of the latter.

CD4 T-cells, unlike their CD8 counterparts, are involved in both the humoral and cell-mediated arms of adaptive immunity. These CD4 cells drive isotype switching, a process that changes the types of antibodies produced after initial exposure to a pathogen to increase their molecular affinity. Additionally, CD4 cells promote the activity of macrophages to directly digest invading pathogens.

After isotype switching facilitates the production of new serum antibody types by B-cells, an experiment shows that antibodies bind more tightly to pathogens. The researcher conducting the experiment concludes that these new antibodies are more efficient at interrupting infection than were the antibodies produced immediately following initial exposure to the pathogen. Which of the following is the most likely?

Possible Answers:

IgG was produced immediately after initial pathogen exposure, while IgM was produced after isotype switching

IgM was produced immediately after initial pathogen exposure, while IgG was produced after isotype switching

IgM was produced immediately after initial pathogen exposure, while IgA was produced after isotype switching

IgA was produced immediately after initial pathogen exposure, while IgG was produced after isotype switching

IgA was produced immediately after initial pathogen exposure, while IgM was produced after isotype switching

Correct answer:

IgM was produced immediately after initial pathogen exposure, while IgG was produced after isotype switching

Explanation:

The question specifies that the antibodies in question are serum antibodies, while IgA is primarily an antibody type secreted into luminal environments. As a result, we can conclude that IgA is not likely to be involved at all in this experiment. Beyond this, you must know that IgM is the type of antibody that is produced upon initial pathogen exposure. After CD4 cells facilitate isotype switching, IgG is produced and demonstrates more robust binding.

Example Question #4 : Help With Antigens, Antibodies, And Mh Cs

The human immune system is organized along two broad arms: innate immunity and adaptive immunity. The differences between these two approaches to immunity are not always black and white, but can be described in general terms with regard to immunological memory. Adaptive immunity displays this type of memory, and mounts a more intense response to pathogens upon second and subsequent exposures.

Within adaptive immunity, the system is further divided into humoral immunity and cell-mediated immunity. We can say that antibodies are the primary mediators of the former, while CD8 T-cell based cytotoxicity is the mediator of the latter.

CD4 T-cells, unlike their CD8 counterparts, are involved in both the humoral and cell-mediated arms of adaptive immunity. These CD4 cells drive isotype switching, a process that changes the types of antibodies produced after initial exposure to a pathogen to increase their molecular affinity. Additionally, CD4 cells promote the activity of macrophages to directly digest invading pathogens.

A scientist is conducting an experiment with a bacterial cell that stimulates an antibody response in mice. The scientist is able to isolate the particular region of the bacterial cell that generates the response and binds to the antibody. This portion of the bacterial cell is best described as the __________.

Possible Answers:

epitope

variable region

light chain

constant region

heavy chain

Correct answer:

epitope

Explanation:

The epitope is the region of a target cell to which an antibody binds. The remaining choices are all structural regions of the antibody itself, as opposed to the target cells to which an antibody binds.

Example Question #5 : Help With Antigens, Antibodies, And Mh Cs

Which antibody is able to cross the placenta? 

Possible Answers:

IgA

IgE

IgD 

IgM 

IgG 

Correct answer:

IgG 

Explanation:

IgG is the only class of immunoglobulin that is able to cross the placenta. This is important as this immunoglobulin is able to provide passive immunity to the unborn fetus

Example Question #6 : Help With Antigens, Antibodies, And Mh Cs

MHC I is found on which cell types?

Possible Answers:

All nucleated cells 

Antigen presenting cells only 

B cells only

None of the other answers 

Phagocytic cells only 

Correct answer:

All nucleated cells 

Explanation:

MHC I is found on all nucleated cells and presents antigens to cytotoxic T lymphocytes. These cytotoxic T cells contain CD8 receptors, which binds to MHC I. MHC II cells are found on B-lymphocytes and antigen presenting cells only. MHC II presents antigens to helper T cells, which contain CD4 receptors. 

Example Question #7 : Help With Antigens, Antibodies, And Mh Cs

What type of immunoglobulin plays an important role in the allergic response?

Possible Answers:

IgE

IgM

IgG

IgE

IgD 

Correct answer:

IgE

Explanation:

IgE is able to bind via the (fragment crystallizable) Fc region to mast cells and basophils. This binding allows these cells to release their granule contents involved in many allergic reactions. 

Example Question #8 : Help With Antigens, Antibodies, And Mh Cs

Immunoglobin M (IgM) __________.

Possible Answers:

binds to mast cells and basophils 

is the first antibody produced in response to an infection 

is a monomer 

is the most abundant class in the blood and tissue fluids 

has the ability to cross the placenta 

Correct answer:

is the first antibody produced in response to an infection 

Explanation:

IgM is the first antibody produced during the primary immune response. It is the only immunoglobulin whose shape is a pentamer. IgG is the most abundant immunoglobulin class in the blood and tissue and has the ability to cross the placenta. IgE binds to basophils and mast cells and is involved in the allergic response. 

Example Question #9 : Help With Antigens, Antibodies, And Mh Cs

A patient has A positive blood type. What type of blood can this patient receive?

Possible Answers:

None of these

AB positive

O positive

B positive

AB negative

Correct answer:

O positive

Explanation:

For any recipient, we must consider what antibodies they have. A patient with A positive blood has the following antibodies: anti-B For any donor, we must consider what antigens they have. The donor cannot have an antigen that matches the recipient's antibodies, or else agglutination will occur. Therefore, any B blood types will result in agglutination. The O positive person only expresses the Rh antigen, and the recipient does not express this antibody. No agglutination will occur.

Example Question #10 : Help With Antigens, Antibodies, And Mh Cs

A patient with O negative blood needs a transfusion. What blood type can they safely receive?

Possible Answers:

B negative

None of these

B positive

A negative

AB negative

Correct answer:

None of these

Explanation:

A person with O negative blood is known as the universal donor because their blood cells completely lack antigens. This means their blood cannot be recognized as foreign by a donor. For blood transfusions, we must keep in mind the recipient's antibodies. For an O negative recipient, he/she produces A and B antigens, and Rh antigens if they have been previously exposed to Rh positive blood. That means they cannot accept blood from donors with A, B or possibly Rh positive blood. They must receive O negative blood only.

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