Question 1

Which of the following statements about epitopes is FALSE?

Accepted Answer

There can be multiple epitopes on a single antigen, so there is not a one-to-one correspondence between antigen and epitope.

Question 2

Mast cells can both constrict and dilate blood vessels after injury. Which of the following best explains why both of these events occur shortly after tissue is injured?

Accepted Answer

C

Question 3

Differences in the B- cell receptors of two different B cells are due to

Accepted Answer

Differences in the B-cell receptors of two different B cells are due to the recombination of variable regions of the light-chain and heavy-chain genes, which leads to the generation of unique amino acid sequences in the antigen-binding site. This process is known as V(D)J recombination and occurs randomly during B-cell development in the bone marrow. It is the reason why each B cell can recognize a different antigen. The other options, such as rearrangement of C-region genes, antigen-presenting cells, patient reaction, or mutation induced by exposure to the antigen, do not explain the variability in B-cell receptors.

Question 4

You and a friend are in line for a movie when you notice the woman in front of you sneezing and coughing. Both of you have been equally exposed to the woman's virus, but over the next few days, only your friend acquires flu- like symptoms and is ill for almost a week before recovering. Which one of the following is a logical explanation for this?

Accepted Answer

It is likely that you have been previously exposed to the virus and your immune system has developed antibodies to fight against it, providing a level of protection. This is known as acquired immunity. Your friend, on the other hand, may not have been exposed to the virus before or may have a weaker immune system that was unable to fight off the virus effectively, leading to them becoming ill. Option A is incorrect because innate immunity is not specific to a particular virus and would not explain the difference in response between you and your friend. Option C is also incorrect since it implies that your friend lacks the ability to fight off the virus entirely, which is unlikely. Option D is incorrect because option C is not a valid explanation for the difference in response.

Question 5

A newborn who is accidentally given a drug that destroys the thymus would most likely

Accepted Answer

The thymus is where T cells differentiate and mature. If the thymus is destroyed by a drug, the newborn would be unable to differentiate and mature T cells, leading to a lack of adaptive immunity. This would most likely result in increased susceptibility to infections, especially viral infections, which are typically controlled by T cells. The other choices are incorrect because B cells develop in the bone marrow, innate immunity does not rely on the thymus, MHC molecules are not directly affected by thymus function, and genetic rearrangement of antigen receptors occurs in both B and T cells.

Question 6

It is commonly know that breast milk provides many benefits to a newborn baby because it provides immune benefits. Which of the following immunoglobulins play a role in this?

Accepted Answer

Immunoglobulin A (IgA) is found in high levels in breast milk and plays a crucial role in protecting the baby's gut, respiratory, and urinary tract from infections.

Question 7

A small child falls down and cuts his knee. A few days later a scab forms over the wound. After a few weeks, the wound does not appear to be healing, but it is not infected. Which of the following could explain this?

Accepted Answer

Cytokines are crucial for the wound healing process as they help in the regulation of the phases of wound healing, including inflammation, proliferation, and remodeling. Neutrophils are also important in the initial phase of wound healing, particularly in preventing infection and cleaning the wound. A deficiency in either cytokines or neutrophils could impair the healing process, even if the wound is not infected.

Question 8

Mucous occurs in both the respiratory and digestive tracts. What is its main immunological function?

Accepted Answer

Mucous acts as a physical barrier, trapping pathogens and preventing them from entering the body. It also contains immune cells and antibodies that can directly attack and destroy pathogens.

Question 9

Which of the following pairs of proteins shares the most overall similarity in structure?

Accepted Answer

B-cell receptors and antibodies are both immunoglobulin proteins and share a high degree of similarity in structure, with the exception that antibodies have an additional constant region. T-cell receptors are structurally different from antibodies and B-cell receptors. Antibodies and antigens are not proteins, but rather the antigen is the target recognized by the protein antibodies.

Question 10

Lymphocytes are formed in what organs)?

Accepted Answer

Lymphocytes are primarily formed in the bone marrow and the thymus. In the bone marrow, both B cells and T cells are originated, but T cells migrate to the thymus to mature.

Question 11

Which of the following would put you at increased risk of pathogens entering your body?

Accepted Answer

All of the options listed would increase the risk of pathogens entering your body. Lysozyme is an enzyme that destroys bacteria; without it, you're more susceptible to infections. Earwax serves as a barrier to pathogens, and removing it daily can make the ear canal more vulnerable. Mucus traps pathogens, and if it's too watery, it may not perform this function effectively, allowing more pathogens to enter.

Question 12

Which of the following best describes what an antigen is?

Accepted Answer

An antigen is a molecule, such as a polypeptide or carbohydrate, that initiates a response from the immune system. It is typically a foreign substance that elicits an immune response, but can also be a self-antigen that triggers an autoimmune response. Antigens are recognized by the immune system based on their unique features or epitopes.

Question 13

Arrange in the correct sequence each of the following components of the mammalian immune system as it first responds to a pathogen.
I. Pathogen is destroyed.
II. Lymphocytes secrete antibodies.
III. Antigens from the pathogen bind to receptors on lymphocytes.
IV. Lymphocytes specific to antigens from the pathogen become numerous.
V. Only memory cells remain.

Accepted Answer

The correct sequence for the mammalian immune system's response to a pathogen starts with antigens from the pathogen binding to receptors on lymphocytes (III), followed by the proliferation of lymphocytes specific to the pathogen's antigens (IV), then these lymphocytes secrete antibodies (II), leading to the destruction of the pathogen (I), and finally, only memory cells remain (V) for a quicker response if the pathogen is encountered again.

Question 14

If you were developing artificial B- cell receptors BCRs) based on the natural version and wanted to change the BCRs' ability to bind certain antigens, which region of the natural receptor would you alter?

Accepted Answer

The amino terminus of the light and heavy chains of the natural BCRs contain the antigen-binding site, which is responsible for recognizing and binding specific antigens. By altering this region, one can modify the BCRs' ability to bind certain antigens.

Question 15

What do neutrophils and macrophages have in common?

Accepted Answer

Both neutrophils and macrophages are phagocytic cells that can ingest and kill bacteria.

Question 16

What major advantage is conveyed by having a system of acquired immunity?

Accepted Answer

The acquired immune system provides both rapid defense against previously encountered antigens (Answer A) and precise specificity for defense against antigens (Answer C). Therefore, the best choice is E, as both Answer A and Answer C are correct. Answer B is incorrect because the acquired immune system does not provide instant defense against all pathogens.

Question 17

You cut your finger, and after putting pressure on the wound for several minutes, you notice that it is still bleeding profusely. What may be the problem?

Accepted Answer

The problem may be that platelets are not functioning properly or there are too few to be effective, as platelets are responsible for clotting and stopping bleeding. Mast cells and antigens are not directly involved in clotting.

Question 18

You are playing a new video game that is based on the human immune system. The player is inside a human, and you must successfully fend off invading pathogens in a quest to find the "Golden Antibody." At level 1, your arsenal for fighting off pathogens consists only of the innate immunity leukocytes and their various secretions. If the enemy has killed off most of your neutrophils and macrophages, which of the following should you utilize to recruit more of these leukocytes to the battle?

Accepted Answer

Cytokines are signaling molecules that help recruit and activate leukocytes, including neutrophils and macrophages, to the site of infection. Therefore, utilizing cytokines would be the best choice to recruit more of these leukocytes to the battle. Bone marrow produces leukocytes but may not be immediately accessible in the game. Reactive oxygen species, platelets, and histamine are involved in immunity but not specifically in recruiting neutrophils and macrophages.

Question 19

Which of the following is the best definition of autoimmune disease?

Accepted Answer

Autoimmune disease is a condition in which the immune system recognizes and attacks self-antigens, mistaking them for foreign antigens. This results in tissue damage and inflammation in various parts of the body. In autoimmune diseases, a molecule belonging to the host is treated like an antigen and triggers an immune response, leading to the destruction of self-tissue.

Question 20

Which of the following statements is not fundamental to the clonal- selection theory of how the acquired immune system functions?

Accepted Answer

The clonal-selection theory does not include the statement that cloned lymphocytes have slight differences and are selected by the spleen for removal if they do not bind an antigen. The theory states that the selected clones persist and proliferate, while those that do not recognize an antigen undergo apoptosis.

Quiz 48: The Immune System in Animals