AP Biology : Understanding the Adaptive Immune Response

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding The Adaptive Immune Response

Which of the following statements best represents antigen presentation in an acquired immune response to a pathogen?

Possible Answers:

Antigen presenting-cells present antigens memory helper T-cells, followed by memory B-cells followed, by memory T-cells

Antigen from the pathogen is presented to memory helper T-cells to stimulate a new round of B-cell clonal selection and antibody response

Antigen from the pathogen is presented specifically to memory T-cells to activate cytotoxic T-cells to clear the infection

Antigen from the pathogen is presented simultaneously to memory helper T-Cells, memory T-cells, and memory B-cells

Correct answer:

Antigen from the pathogen is presented simultaneously to memory helper T-Cells, memory T-cells, and memory B-cells

Explanation:

An acquired immune response to a secondary infection by a pathogen results in presentation of antigen to residual memory helper T-cells, memory T-cells, and memory B-cells. Upon recognizing the antigen, memory T-cells can become cytotoxic T-cells and target the infected region. The process of presentation promotes direct expansion of the existing population of immune cells already capable of responding to the pathogen. Immunological memory provides a more rapid response time to combat the pathogen during the second exposure.

Example Question #4 : Immune System

Once an individual becomes exposed to a pathogen, the body's immune system responds faster against a second exposure to the same pathogen. Why does this occur?

Possible Answers:

Specific lymphocytes quickly produce the proper antibodies

Innate defenses are strengthened

The proper antibodies are constantly circulating in the blood

Stimulated memory cells quickly engulf pathogens

Pathogens are changed so they are no longer harmful

Correct answer:

Specific lymphocytes quickly produce the proper antibodies

Explanation:

Innate defenses, such as skin and macrophages, are a primary defense against all diseases, but adaptive immunity is related to exposure to a specific disease. The ability for the body to produce specific antibodies quickly provides adaptive immunity. While some antibodies may remain in the blood after initial exposure, this small amount does not provide sufficient immunity. 

The specific lymphocytes that produce antibodies during a second exposure are called memory B-cells. When an antigen is presented to a memory B-cell that produces the appropriate antibody, the cell divides and differentiates into plasma cells. Plasma cells are then responsible for producing large amounts of antibodies against the specific antigen. Antibodies are cell-surface markers that attach to pathogens, signaling effector cells to rapidly destroy the pathogen. The rapid multiplication of B-cells to generate antibody to a specific threat is known as clonal selection.

Example Question #2 : Understanding The Adaptive Immune Response

Which immune system response could best be characterized as adaptive?

Possible Answers:

The epithelium of the skin blocks most pathogens from ever entering the body

In the inflammatory response, mast cells produce histamine to facilitate the travel of immune cells and plasma to the afflicted area

After the first exposure to an antigen, memory B-lymphocytes are produced to recognize the same antigen upon a second exposure

A phagocyte engulfs and destroys bacteria, dead cells, and other potentially harmful particles that it encounters

Correct answer:

After the first exposure to an antigen, memory B-lymphocytes are produced to recognize the same antigen upon a second exposure

Explanation:

The two types of immune system responses are innate (nonspecific) and adaptive (specific). Innate responses are those that act on many pathogens in the same general way. For example, the skin and the mucus in the nasal cavity both physically block the entry of pathogens into the body, but they do not specifically target certain antigens. Other examples of the innate response are inflammation and the general activity of phagocytes. On the other hand, the adaptive immune system provides a second line of defense against certain, previously encountered pathogens. Here, the only answer choice that deals with the recognition of specific antigens is the production of memory B-lymphocytes. The adaptive immune response generally involves T-lymphocytes, B-lymphocytes, antigens, and antibodies.

Example Question #3 : Understanding The Adaptive Immune Response

Which cell is responsible for stimulating differentiation of B-lymphocytes into specialized plasma cells?

Possible Answers:

Memory B-cells

Helper T-cells

Antibodies

Cytotoxic T-cells

Correct answer:

Helper T-cells

Explanation:

The differentiation of many acquired immune cells is largely dependent on helper T-cells. In the presence of a matching antigen, B-lymphocytes can be differentiated into plasma cells and memory B-cells with the assistance of helper T-cells. Memory B-cells are easily triggered if an antigen is presented during a second infection, while plasma cells are the final differentiated form of a B-cell responsible for mass-producing antibodies. Helper T-cells are also important in the activation of cytotoxic T-cells, which detect antibody-antigen complexes on cell membranes and help to destroy these tagged cells.

Example Question #4 : Understanding The Adaptive Immune Response

Which of the following is a characteristic of acquired immunity?

Possible Answers:

Recognition of traits specific to a particular pathogen

Response is driven by phagocytic cells

Use of basophils and mast cells to create inflammation

Acquired immunity is a rapid response

Recognition of shared traits by a wide array of pathogens

Correct answer:

Recognition of traits specific to a particular pathogen

Explanation:

Acquired, or adaptive, immunity is a second immune defense system and develops slowly after exposure to an initial infection. As a result, the immune system is "trained" and capable of recognizing many specific components or antigens from the pathogen. Acquired immunity stores the information from an initial infection in preparation for reintroduction of the pathogen; it does not immediately respond to the initial infection.

Upon reinfection or exposure to a pathogen, the acquired immunity is better able to detect and defend the body. This includes the generation of antibodies that can bind a pathogen and cytotoxic T-lymphocytes that can detect and eliminate infected cells.

Acquired immunity is balanced by innate immunity, which responds indiscriminately to all pathogens. Innate immunity is essential for fighting and preventing initial infections, before adaptive immunity has learned to recognize the specific pathogen present.

Example Question #5 : Understanding The Adaptive Immune Response

Major histocompatibility molecules (MHC) are critical for the functioning of the immune system. These proteins are utilized allow for communication between the immune system and the cells. MHC I are utilized to show which cells are in fact part of the body and which are foreign. MHC II are utilized to show the immune system when there is an intruder.

MHC I molecules are derived from chromosome 6. On chromosome 6, there is a specific gene that encodes for the molecule. On the gene, there are 3 locus (A, B, C) which allows for variability in the binding site of the MHC I molecule. The MHC gene is co-dominance and therefore adds to its diversity. During development, the gene is transcribed into MHC I molecules. However, some of these are broken down and react with a particular MHC I molecule. The reaction allows for the MHC I molecule to surface onto the cellular membrane and to self-identify the protein for the cytotoxic T-cell.

After translation, MHC II molecules are transported to the endosome. When a pathogen binds to the proper MHC II binding site, these molecules are then presented to T-Helper cells. In comparison, MHC I molecules interact with endogenous antigens whereas MHC II molecules interact with exogenous antigens.

Patient A has a disorder which resulted in a nondisjunction of chromosome 6. Which might this disorder lower the chances of developing an autoimmune disease? 

Possible Answers:

Increase variability of MHC I binding site  

Increase variability of MHC II binding site  

Decrease  variability of MHC II binding site  

None of these

Decrease variability of MHC I binding site  

Correct answer:

Increase variability of MHC I binding site  

Explanation:

Since the genes in chromosome 6 is codominance, each gene will be expressed. With nondisjunction, there will be an extra chromosome. This will result in all three genes being expressed. The expression of all three genes will increase the diversity of the MHC I pool. Recall MHC I is responsible for notifying which cells are related to the body to prevent autoimmunity. 

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