Chapter 16: Adaptive Immunity - Reading Quiz/Homework

Which of the following must an immature T cell do in order to survive and enter the periphery?

-recognize "self" MHC molecules -not react strongly with self proteins

A primary antibody response is initiated following exposure to a pathogen for the first time. Order the primary antibody response below.

1. Foreign antigen binds B cell with appropriate antibody. 2. B cells become activated and differentiate into plasma and memory cells. 3. Low-affinity IgM is produced and secreted into serum 4. Isotype switching occurs. 5. Large quantities of IgG are produced and secreted into serum. 6. Plasma cells die.

In which of the following scenarios would you expect capping to occur?

Answer: A B cell contacts a microbe with multiple copies of the same epitope. Explanation: Capping occurs when adjacent B-cell receptors bind adjacent epitopes on a microbe. Capping is T-cell independent and leads to activation of the B cell.

A child receives her first diphtheria vaccine when she is 5 years old. Four weeks later, she receives a booster dose. One week after receiving the booster vaccine, her physician checks her serum titer to see if she is responding normally. Which of the following would indicate a normal response? https://cdn.wwnorton.com/college/biology/humanexperience/img/visualquiz/AQ1605.jpg

Answer: A. elevated levels of both IgM and IgG Explanation: IgM levels rise initially after primary vaccination and booster doses before dropping off to a level near zero. After primary vaccination, IgG levels rise more slowly than IgM levels, but IgG levels are higher than IgM levels and remain elevated longer. After a booster dose, IgG levels rise more rapidly than IgM levels, increase to much higher levels than IgM, and remain elevated.

How are B cells able to respond to millions of different antigens?

Answer: B cells randomly rearrange immunoglobulin genes to make unique antigen-binding sites. Explanation: Antigen-binding site diversity is produced when progenitor B cells randomly rearrange sets of immunoglobulin genes. Each person has approximately 1,000 immunoglobulin genes or gene sets that can be rearranged to form millions of different antigen-binding sites. Individual B cells are only capable of binding to one epitope.

What are memory B cells?

B cells primed to become plasma cells if activated again in the future

B-Cell Differentiation process

1. each B cell rearranges its DNA to create a unique B cell receptor 2. B cells digest antigens that are bound to the antibodies on their surface 3. B cells display antigens and MHC Class 2 receptors on the cell surface 4. B cells become activated by interacting with helper T cell 5. B cells undergo clonal selections six antibodies released by plasma cells bind to antigen so they will be destroyed by other immune system cells

Identify the components that contribute to the activation of cytotoxic T cell

A. virally infected a PC B. MHC Class 1 receptor C CD8 receptor D. T cell receptor (TCR) E. viral antigen F. helper T cell secreting simultaneously

There are two types of major histocompatibility complexes (MHCs): class I and class II. Which characteristics below describe MHC class I and which describe MHC class II?

Answer: MHC class I -Interact with CD8 -Found on all nucleated cells -Antigens come from the ER -Displays endogenous antigen -Present antigen to cytotoxic T cells MHC class II -Interact with CD4-Found only on APCs-Antigens come from the lysosomes-Displays exogenous antigen -Present antigen to helper T cells

Put the following types of organic molecules in order from the most antigenic (immunogenic) to the least antigenic.

Answer: -Proteins -carbohydrate polymers -lipid molecules -small inorganic molecules (ex: drugs) Explanation: Correct! Proteins tend to make the best antigens. They are large with stable and unique shapes. Carbohydrates vary in size and shape and therefore also vary in how antigenic they are. Lipids tend to be poor antigens, while small molecules are usually too little for the immune system to notice.

Which of the following statements correctly describes immunogens?

Answer: All immunogens are antigens. Explanation: Antigens are molecules that elicit the synthesis of antibodies. All immunogens are antigens, but not all antigens are immunogens. Some antigens are small molecules called haptens, which must be attached to an immunogen to elicit an immune response.

Which of the following would be two antibodies of different isotypes?

Answer: An IgG antibody and an IgA antibody that bind to the same antigen and were created by plasma cells that descended from the same activated B cell. Explination: Correct; IgG and IgA are different classes or "isotypes" of antibodies. A single person has five antibody isotypes: IgG, IgA, IgM, IgE and IgD.

The rapid strep test takes about 5 minutes and is positive in the presence of a cell wall sugar specific to GAS (e.g., Streptococcus pyogenes). Which type of test is the rapid strep test?

Answer: Antigen Explination: Correct; during an infection, antibodies are generated in response to specific foreign antigens (e.g., the cell wall carbohydrates of GAS). The specificity of antibodies for a particular antigen forms the basis for many diagnostic tests.

The binding of the T-cell receptor (TCR) of a TH0 cell to an antigen-MHC complex is not enough to activate the TH0 cell. A second activation signal involves an interaction between a ___________ molecule on the T cell and a ___________ molecule on the antigen-presenting cell.

Answer: CD28; B7 -a CD28 molecule on the T cell and a B7 molecule on the antigen-presenting cell. Explanation: Two interactions must occur for TH0 cells to become activated. The first interaction involves linking a T-cell receptor to an antigen-MHC II complex on an antigen-presenting cell (APC). The second interaction involves linking a CD28 on the T-cell surface to a B7 protein on the APC surface.

Rheumatic fever can occur as a serious complication of inadequately treated strep throat and scarlet fever. It may occur from two to four weeks after a primary GAS infection, and in some cases causes significant heart damage. Which of the following represents the most reasonable explanation for why this occurs?

Answer: Certain proteins on heart valves bear similarities to S. pyogenes antigens. Explanation: Correct; cross-reaction of anti-streptococcal antibodies with cardiac (and joint) tissue elicits a strong inflammatory response which causes the resultant damage. Fortunately, this complication is rare in persons treated with antibiotics.

Which of the following combinations is correctly matched?

Answer: Class I MHC molecules bind intracellular antigen for presentation to CD8 T cells. Explanation: Class I MHC presents intracellular antigen to CD8 T cells. Class II MHC molecules present extracellular antigen to CD4 T cells.

What do granzymes do?

Answer: Granzymes stimulate cell death in infected cells. Explination: When a cytotoxic T cell is able to bind to antigen in the MHC class I receptor on an infected cell, it stimulates the release of perforin and granzymes. These factors work together to kill the target cell so that it and the replicating virus inside it are destroyed.

Jamal is vaccinated against varicella, also known as chicken pox, as a young child. If he has subsequent exposure to the varicella virus as an adult, what would you expect to occur?

Answer: His titer levels of IgG would be much higher than they were after vaccination. Explanation: Vaccination stimulates a primary immune response. During a secondary immune response, subsequent exposure would lead to class switching from IgM production to IgG production, and IgG antibodies would be secreted at much higher levels.

What is the relationship between the humoral and cellular branches of immunity?

Answer: Humoral and cellular immunity are intertwined, each relying on some facet of the other to work properly. Explanation: both branches of the immune system are intertwined and rely on each other for proper function. B cells and the antibodies they produce are part of the humoral immune system, while T cells are part of cellular immunity. Neither cell type can achieve its full purpose without interacting with the other.

Which of the following cytokines must be present to continue a cell-mediated, cytotoxic T-cell response?

Answer: IL-2 Explanation: The second signal in cytotoxic T-cell activation is secretion of IL-2 by helper T cells.

Breast milk and colostrum (early breast milk) provide passive immunity to infants in the form of ___________ antibodies.

Answer: IgA Explination: IgA is secreted across mucosal surfaces and is found in tears, breast milk, and saliva. Passive immunity occurs when babies receive IgG through the placenta and IgA through breast milk.

Why are lipids less immunogenic than proteins?

Answer: Lipids are more flexible and uniform than proteins. Explination: Proteins are the strongest antigens because they form a variety of shapes, they maintain tertiary structures, and they are made of amino acids in different combinations. Lipids and nucleic acids tend to be weaker antigens because they are more flexible and their subunits are relatively uniform.

For years, it was believed that streptococci were exclusively extracellular pathogens. It is now well documented that certain strains are capable of invading and persisting within epithelial cells of the respiratory tract. An infected epithelial cell should, however, be able to alert the immune system to its status by presenting bacterial antigens on

Answer: MCH I Explanation: All nucleated cells in the body can process intracellular antigens of foreign origin and load them onto MHC I molecules. The MHC I complexes are then transported to the cell membrane where the outward-facing antigens can be recognized by T cells via their TCRs (T-cell receptors). Only certain phagocytic cells such as macrophages, neutrophils, and dendritic cells also process and present antigens on MHC II molecules. Antibodies are produced exclusively by B cells, and haptens are small antigens that are not immunogenic until complexed with a larger carrier protein.

Which of the following statements describes the appearance of a plasma cell?

Answer: Plasma cells have much more endoplasmic reticulum than naive B cells to support the increased need for protein synthesis Explination: Correct; ribosomes bound to the rough ER synthesize the antibody molecules that will be secreted to fight infection.

Which of the cell types from the list below would NOT express MHC class I receptors?

Answer: Red blood cells Explination: Correct; with the exception of RBCs, all cells in the body express MHC class I receptors. RBCs do not have a nucleus and do not express new proteins, so they would have nothing to display in an MHC class I receptor.

A cytokine storm may occur when

Answer: Superantigens bind non-specifically to T-cell receptors. Explanation: Excessive cytokine production, called a cytokine storm, may occur when one cytokine stimulates other cells to make more cytokines or when a superantigen binds T-cell receptors and MHC molecules on antigen-presenting cells nonspecifically. The phenomenon can have negative effects on host cells.

T cells capable of activating cytotoxic T cells are known as

Answer: TH1 cells. Explanation: The major function of TH1 cells is activation of cytotoxic T cells. The major function of Treg cells is anti-inflammatory, the major function of TH2 cells is helping B cells, and the major function of TH0 cells is differentiation into TH1 or TH2 cells.

What kind of infection would cell-mediated immunity most effectively clear?

Answer: The flu (caused by the influenza virus) Explination: Correct; viral infections are fought by killing infected host cells. Cytotoxic T cells used by cell-mediated immunity can kill host cells.

How long does it take for an adaptive immune response to develop when a new pathogen enters the body?

Answer: 3-4 days Explanation: an adaptive immune response will develop over several days following the exposure to a new antigen.

Bobby woke up this morning with a fever and body aches. He felt fine yesterday. Considering his sudden onset of symptoms, which of the following would be true regarding his body's immune response?

Answers: -His initial reaction to the new antigen would be called a primary response. - it if his doctor has ruled out allergies and or parasitic infection as the cause of symptoms then his IgE concentration would be low -his blood test would most likely reveal a high concentration of IgM

T-cell activation requires binding to specific antigens. Where must those antigens be found for activation of helper T cells?

Presented by MHC class II receptors

Identify the location in the lymphatic system where each of the following activities is expected to take place

Primary response activates naive B cells begins with the production of IGN lower affinity antibodies takes several days secondary response begins with the production of IgG activate memory B cells begins immediately high affinitity antibodie

How are antigens processed before binding to MHC class I molecules?

They are digested in the cytoplasm of the cell by the proteasome.

Put the steps of B-cell activation in the correct order from first to last.

antigen recognition-B cell exposed to antigen and binds with matching complementary. antigen presentation-B cell displays epitope, Helper T cell binds secretes interleukin. clonal selection= interleukin stimulates B cell to divide. differentiation=become memory or plasma cells. attack- plasma cells secrete antibody.

Zika is an emerging virus that has been linked to severe birth defects (e.g., microencephaly) in infants born to affected mothers. Imagine a situation where anti-Zika IgG, but not IgM, is detected in serological tests on both the mother and her newborn. How would these results be best interpreted?

Answer: The mother had a prior exposure to Zika, but so far, there is no sign of fetal infection. Explanation: Correct; IgG (but not IgM) antibodies produced from a prior exposure to a pathogen can cross the placental barrier to provide passive immunity to a developing fetus. The lack of IgM in the newborn suggests (but cannot be interpreted as proof) that the baby was not exposed in utero. This conclusion is strengthened by the observation that IgM is often detected in exposed fetuses after levels drop below detection in the mother—who is better able to fight the infection. This is because viral persistence in the womb results in the sustained production of IgM as new naïve B cells are continually activated.

A small fraction of self-reactive T cells escape negative selection and become

Answer: Treg cells. Explanation: Regulatory T cells (Treg cells) are self-reactive T cells that are useful in blocking activation of autoimmune lymphocytes.

If you compare isotypes found in one human to isotypes in another human, you will find slight differences in amino acids. These differences are called

Answer: allotypes Explanation: An allotype is diversity between individuals of the same species. Isotypes are antibody diversity seen between different species. Idiotypes are the diversity seen within an individual.

The body's immune response to a microbe is really multiple responses to multiple small regions of that microbe. Each small region that is recognized by a specific component of the immune system is referred to as what?

Answer: an epitope Explanation: each antibody binds to a specific epitope on the microbe or antigen.

Which of the following molecules is NOT included in the immunoglobulin superfamily of proteins? a) immunoglobulins b) major histocompatibility proteins c) B-cell receptors d) antigens

Answer: antigens Explanation: The immunoglobulin superfamily of proteins includes antibodies (also known as immunoglobulins), major histocompatibility proteins, B-cell receptors, and T-cell receptors.

What is the first molecular signal required for TC cell activation?

Answer: binding of a T-cell receptor to an antigen-MHC I complex on an antigen-presenting cell Explanation: Two molecular signals are required for activation of TC cells. The first signal involves binding of the T-cell receptor (TCR) to an antigen-presenting cell (APC). CD8 molecules on the TC cell allow this binding to class I MHC on the APC to occur. The second signal is the secretion of the cytokine IL-2 from TH1 cells.

What event leads directly to the binding of a CD40 protein on a B cell to a CD40 ligand on a T cell?

Answer: binding of a T-cell receptor to an antigen-MHC II complex on a B-cell Explanation: Although internalization of antigen by the B cell would precede the binding of a CD40 protein with a CD40 ligand, the antigen must first be presented on the surface of the B cell. The step leading directly to the binding of CD40 and CD40 ligand is the binding of a T-cell receptor to an antigen-MHC II complex on a B cell.

Patients who have functioning T cells but dysfunctional B cells will retain

Answer: cell-mediated immunity. Explination: B cells are responsible for the production of antibodies during a humoral immunity response. The specific cells that secrete antibodies are differentiated B cells known as plasma cells. T cells are responsible for cell-mediated immunity.

All nucleated cells in a human body normally have

Answer: class I MHC molecules. Explanation: Class I MHC molecules are found on the surface of all nucleated cells. Class II MHC molecules are found on the surface of antigen-presenting cells (dendritic cells, macrophages, and B cells). MHC molecules are used to present antigen to T cells. CD4 and CD8 are most often found on T cells.

Which of the following occurs after a B cell binds to an epitope?

Answer: clonal expansion of the activated B cell Explination: When a B-cell receptor binds to an antigen epitope, the B cell becomes activated and undergoes clonal expansion. Some of the clones produced will differentiate into antibody-secreting plasma cells. Other clones will become memory B cells.

This figure illustrates a single step in antibody formation within a lymph node. What is the immediate outcome of this step?

Answer: heavy-chain class switching Explanation: This is one step in the process of T-cell dependent activation of a B cell. This interaction leads to heavy-chain class switching in the B cell. Prior to this step, the B cell bound the same antigen recognized by the TH cell shown.

Which of the following is considered a "professional" antigen-presenting cell (APC)?

Answer: macrophage Explination: Macrophages, dendritic cells, mast cells, and B cells are considered "professional" APCs.

Which of the following cellular defects might result in MHC class II molecules being loaded with endogenous (instead of exogenous) antigens?

Answer: premature digestion of invariant chains Explanation: Correct; because MHC molecules themselves are not selective, premature digestion of the invariant chain would permit inappropriate binding of endogenous antigens. The invariant chain also facilitates fusion with the endosomes containing engulfed foreign material. The degraded proteins in these vesicles are then loaded onto MHC II for presentation on the cell surface.

An individual has repeated exposure to the mumps virus. Upon examination of that individual, you would expect to find that his or her memory B cells would

Answer: produce antibodies with higher affinity than the original B cell that bound to the mumps virus. Explanation: Antibodies of higher affinity would be found because B cells with repeated exposure to the same antigen would undergo a process known as affinity maturation. Random mutations could increase or decrease the affinity of the antibodies produced during a secondary immune response. B cells producing antibodies with the greatest affinity would undergo clonal expansion and be maintained as memory B cells.

How are T-cell receptors (TCRs) used in B-cell activation?

Answer: to help initiate heavy-chain class switching in B cells Explanation: B cells present antigen-MHC II complexes to activated helper T (TH) cells that can bind to the same antigen to which the B cell can bind. TH cells use T-cell receptors (TCRs) to bind to the presented antigen. In response, B cells undergo class switching and differentiation.

Which of the processes below are parts of the humoral immune response, and which are parts of the cell-mediated immune response? Indicate your answer by dragging the labels to the appropriate bins.

HUMORAL IMMUNITY -The production of memory B-cells -The production of plasma cells -Activation of B-cells -Killing most types of bacteria CELL-MEDIATED IMMUNITY -Cytokine activation of macrophages -The activation of killer T-cells-Killing virally infected cells EXPLINATION: Correct; antibodies and the B cells that produce them are parts of the humoral immune system. The activities of the killer T cells and chemical signals to activate phagocytic cells like the macrophages are parts of the cellular branch of the immune system.

Arrange the functions associated with each T Cell Helper T cells Vs Cytotoxic T Cells

Helper T cells fight extracellular bacteria fight worms and other parasites express CD4 bind antigen presented on MHC II activate B cells Cytotoxic T cells 11 eliminate cancer cells fight viral infections express CD8 bind to antigen presented on MHC I kill an infected host cells

Which of the characteristics below are associated with helper T lymphocytes, and which are associated with cytotoxic T lymphocytes? Indicate your answer by dragging the characteristics into the appropriate bin below.

Helper T cells: -Fight extracellular bacteria -Fight worms and other parasites -Express CD4 -Bind antigen presented on MHC II -Activate B cells Cytotoxic T cells: -Eliminate cancer cells -Fight viral infections -Express CD8-Bind to antigen presented on MHC I-Kill infected host cells Explanation: CD4 positive cells bind to MHC II (4 x 2 = 8), and these cells help with the activation and organization of the immune response. CD8 positive cells bind to MHC I (8 x 1 = 8), and these cells kill virally infected and cancerous cells of the body.

MCH Class I MHC class II

MHC Class 1: -interact with CD8 -found on all nucleated cells imagine -antigens come from the ER just turn it on -displays endogenous antigen -present antigen to cytotoxic T cells MHC Class II: -Interact with CD4 -found only on APC's -Antigens come from the lysosomes -display exogenous antigen -present antigen to helper T cells

What is the function of MHC class II receptors?

MHC class II receptors display antigens to helper T cells.

Fatima is missing her MHC class II proteins. Where should these receptors be found?

On macrophages, dendritic cells, and B cells

Both MHC class I receptors and MHC class II receptors are synthesized on the rough ER. What keeps MHC class II receptors from binding to antigens while in the ER?

The MHC class II receptor has its binding site covered by a protein called the invariant chain. Until that is removed, it is unable to bind to any antigens.

What is the result of antibody binding to rhinovirus?

View FIG 16.5 PG. 474 Paragraph 2 Line 5 (2nd scentence) Answer: Rhinovirus is blocked from binding to the ICAM-1 cell receptor. Explination: The binding of antibody onto virus receptor proteins prevents the rhinovirus from binding to the ICAM-1 cell receptor. Blocking the rhinovirus from binding to the cell receptor prevents the virus from entering the cell and replicating. This is one way antibodies protect us.

The antigen shown at the bottom of this figure is capable of eliciting a response from the immune system. Which of the following terms best fills in the blank on the figure?

View PG.471 FIG 16.1 Breakdown of Antigens, Epitopes, and Immunogens: bacterial cell > nucleic acids, lipids, polysaccharides, and proteins are released after phagocytosis >antigens ANSWER: >ANTIGEN WITH 3 EPITOPES Explanation: Epitopes are small segments of an antigen that can be "seen" by the immune system. Amino acids are the building blocks of proteins. Haptens are very small molecules that must be bound to a carrier protein before they can elicit an immune response.

Fatima's bone marrow is making the normal number of helper T cells. Why would the number of helper T cells in her blood be low?

Without MHC class II receptors, the helper T cells cannot proliferate in response to pathogens in the body.

B cells whose Igα and Igβ proteins lack catalytic function would have a decreased ability to do which?

proliferate in response to antigen binding