CH 43
Clonal selection is the division of _____ that have been stimulated by binding to an antigen, which results in the production of cloned _____.
B cells ... plasma cells and memory cells
B cells are involved in the humoral immune response. The flowchart below summarizes the steps involved in B cell activation. Drag the labels to their appropriate locations on the flowchart below. (Note that TCR stands for T cell receptor.)
- A. Antigen-presenting cell presents antigen on class II MHC - B. Helper T cell recognized antigen using TCR and CD4 - C. Helper T cell binds to B cell and releases cytokines - D. B cell presents antigen on class II MHC molecule - E. B cell differentiates not plasma cells and memory cells
Cytotoxic T cells are the effector cells in the cell-mediated immune response. The diagram below summarizes the interaction of a cytotoxic T cell and its target cell. Drag the labels to their appropriate locations on the diagram below using the following steps. Use targets of Group 2 to indicate the types of cells shown. Then, use targets of Group 1 to the remaining targets. The labels under the cell on the left should describe what happens to that cell at each step. The labels under the cell on the right should describe what happens to that cell at each step. Note that TCR stands for T cell receptor.
- A. Cytotoxic T cell - B. Infected cell - C. Recognizes cell using TCR and CD8 - D. Presents antigen on class 1 MHC - E. Releases perforin and granzymes - F. (Undergoes enzyme attack - G. Moves on to destroy another cell - H. Undergoes apoptosis
Which of these binds to receptor molecules on the host cell membrane?
A (Glycoproteins on the viral envelope recognize and bind to receptors on the host cell.)
Select the correct statement about the immune system.
All antigen receptors produced by a single B cell or T cell are identical and bind to the same epitope.
Which option best describes how a viral antigen, like EBV, is recognized by T cells?
An antigen fragment is presented within class I MHC to the T cell receptor.
How does an antihistamine reduce allergy symptoms?
An antihistamine blocks receptors for inflammatory chemicals released from granules within mast cells.
Based on this research, which of the following studies would likely be best to create better treatments for future C. diff outbreaks?
An in-depth study of the gut microbiome in humans.
Which of the following statements about the clonal-selection theory of immune system function is false?
Antigens are recognized by receptor proteins inside the lymphocyte. (This statement is false; antigens are recognized by receptor proteins on the lymphocyte membrane.)
Which secretion is not a barrier that prevents pathogens from entering the body?
Antigens. (Antigens are foreign molecules that initiate an immune response.)
Because antigen receptor genes are randomly rearranged, some immature lymphocytes produce receptors specific for epitopes on the organism's own molecules. Why doesn't the immune system attack these molecules on the body's cells and tissues?
B and T cells with receptors specific for the body's own molecules are destroyed by apoptosis.
Which statement best describes the difference between responses of effector B cells (plasma cells) and those of cytotoxic T cells?
B cells secrete antibodies against a pathogen; cytotoxic T cells kill pathogen-infected host cells.
Each person makes more than 1 million different B cell antigen receptors and more than 10 million different T cell antigen receptors. How is such diversity in antigen receptors generated?
By combining variable elements, the immune system assembles many different receptors from a much smaller collection of parts.
Which of these is reverse transcriptase?
C
How are cytotoxic T lymphocytes (CTLs) produced?
CD8+ T cells divide and differentiate into cytotoxic T lymphocytes.
What is the final step in the cell-mediated response to a viral infection?
Cytotoxic T lymphocytes punch holes in the membranes of infected host cells.
A C. diff outbreak occurs in a nursing home. Which of the following would likely be best to stop the outbreak?
Disinfect all areas for spores.
Which of these is the viral genome?
E (HIV is a RNA virus.)
What is the role of recombinase in generating lymphocyte diversity?
Early in B cell development, recombinase links one light-chain V gene segment to one J gene segment.
The words "antigen" and "virus" are interchangeable.
False (A virus, like other pathogens, has numerous antigens on its surface, so the words "antigen" and "virus" cannot be used interchangeably.)
True or false? The leukocytes of the innate immune system are B cells, macrophages, and neutrophils.
False (The leukocytes of the innate immune system are mast cells, macrophages, and neutrophils.)
A man who has been exposed to the flu virus is tested by his physician. The physician notes that the virus is present but no measurable level of antibodies corresponding to the virus are detected in his body. What might this mean?
He was probably exposed a few days ago and clonal selection has yet to produce plasma cells.
_____ interact with the antigen-class II MHC complex presented by macrophages.
Helper T cells (Specific helper T cells recognize specific antigen-class II MHC complexes. The result of this is an activated helper T cell that stimulates both humoral and cell-mediated immune responses.)
How do cells involved in the humoral response respond to antigen presentation on the surface of a B cell?
Helper T cells recognize the receptor-antigen complex and cause plasma and memory cells to be produced to then produce antibodies.
Acquired immunity involves both a humoral immune response and a cell-mediated immune response. To review the definitions of these immune responses, see Hint 1. Sort the items into the appropriate bins depending on whether they are involved in the humoral response, the cell-mediated response, or both the humoral and the cell-mediated responses. (If you are not sure what some of the items are, see Hint 2.)
Humoral response: - B cells - Antibodies - Plasma cells Cell-Mediated Response: - Cytotoxic T cells Both: - Helper T cells and cytokines - Memory cells - Antigen-presenting cells
Vertebrate immune cells, which are phagocytic, include which of the following? I) neutrophils II) macrophages III) dendritic cells IV) natural killer cells
I, II, and III
Which of the following statements describe a component of the clonal selection theory of how the adaptive immune system functions? I) Each lymphocyte has a unique membrane receptor that recognizes one antigen. II) When the lymphocyte binds an antigen, it is activated and begins dividing to form many identical copies of itself. III) Cloned lymphocytes have slight differences and are selected by the spleen for removal if they do not bind an antigen. IV) Cloned cells descend from an activated lymphocyte and persist even after the pathogen is eliminated.
I, II, and IV
Which of the following are similarities between B cells and T cells? I) Both recognize antigens using immunoglobulin receptors. II) Both undergo clonal selection after encountering an antigen. III) Both maintain an immunological memory of previously encountered antigens.
II and III
Which statement is true about innate immunity?
Innate immunity is the first, and most general, mechanism of protection against pathogens.
Which answer describes an advantage of having a system of adaptive immunity?
It enables a rapid defense against an antigen that has been previously encountered.
While working as a microbiologist, you discover a new species of Clostridium. Which of the following is true?
It is most likely harmless.
How do cells involved in the innate immune response detect the presence of pathogens?
Leukocytes recognize unique molecules on pathogens. (Pattern-recognition receptors on leukocytes recognize and bind to unique molecules on the pathogens, such as the amino acid N-formylmethionine in bacteria. This receptor binding leads to activation of the innate immune response.)
Tissues are immunologically "typed" before an organ transplant to make sure that the donor and recipient match as closely as possible in their __________.
MHC (major histocompatibility complex) proteins
Which protein presents viral antigens on the outer surface of cells?
MHC protein.
Which of the following cells can engulf a pathogen?
Macrophages. (Macrophages are leukocytes that can engulf and digest a pathogen.)
Use the following information to answer the following question. An otherwise healthy student in your class was infected with Epstein Barr virus (EBV) (the virus that causes infectious mononucleosis) when she was a child, at which time she had merely experienced a mild sore throat and swollen lymph nodes in her neck. When she is exposed to EBV again later in life, she does not get sick or develop any symptoms of mononucleosis. Which of the following statements explains why your classmate does not exhibit symptoms of EBV infection?
Memory T cells recognized the virus upon the second exposure and activated cells that destroyed the virally infected cells.
Which of the following events occurs first when a wound that breaks the skin has occurred?
Platelets release proteins that form clots and decrease bleeding.
Which of the following statements about epitopes is incorrect?
There is a one-to-one correspondence between antigen and epitope.
Which is a true statement about memory cells?
They have a longer lifespan than plasma cells.
Which of the following statements best describes the role of mast cells in the inflammatory response?
They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream. (Mast cells release chemicals that dilate nearby capillaries, increasing their permeability and allowing blood components to enter the region from the bloodstream, thus causing localized swelling.)
Which structure is not a component of the adaptive immune system?
Tissues.
The site of inflammation may become swollen due to the increased numbers of cells and fluids at the site and painful due to signals from pain receptors.
True
True or false? B cells were originally isolated from the bursa in chickens, and their function is to produce antibodies; T cells were originally isolated from the thymus in mice, and their functions include killing host cells that are being infected with a virus.
True
You and your friend were equally exposed to a virus, but over the next few days, only your friend acquired flu-like symptoms and was ill for almost a week before recovering. Which one of the following is a logical explanation for this?
You had an immunological memory of that virus.
You are a doctor. A patient presents with diarrhea and tests positive for C. diff. Which of the following is true?
Your patient may or may not have recently taken antibiotics.
Which statement correctly describes the complement system?
a group of proteins that act together in a cascade fashion
Which response is triggered when bacteria enter the body through a small cut in the skin?
activation of a group of proteins called complement
Which of these is absent from insect immunity?
activation of natural killer cells
Use the graphs to answer the following question. Mutant fruit flies that do not make antimicrobial peptides were tested for survival after infection with Neurospora crassa fungi or with Micrococcus luteus bacteria. The mutant flies were also transfected with the genes for antimicrobial peptides (drosomycin or defensin) and tested for survival. Which of the following hypotheses is best supported using the data?
adding the defensin gene to such mutants protects them from death by bacterial infection
Which statement best describes the concept of clonal selection?
an antigen can provoke production of high amounts of specific antibodies
Extracellular pathogens such as viruses and bacteria in body fluids are attacked by __________.
antibodies
An organism that lacks their thymus would ________.
be unable to differentiate and mature T cells
The role of active cytotoxic T cells is to attack __________.
body cells that have been infected
Is this statement supported or not supported by the graph? A third exposure to antigen X will produce an even stronger immune response than the second exposure did.
cannot be determined from the graph
What is the function of reverse transcriptase?
catalyzing the formation of DNA from a RNA template
Which of the following can trigger septic shock?
certain bacterial infections
Innate immunity and adaptive immunity are both __________.
characteristics of all vertebrate animals
Macrophages are __________.
large, phagocytic cells that can leave circulation and enter the tissues of the body
Vaccination increases the number of
lymphocytes with receptors that can bind to the pathogen.
Which of these cells is a phagocytic leukocyte that can engulf a foreign bacterium?
macrophage
Which of the following cells and signaling molecules are involved in the initial stages of the inflammatory response?
mast cells and histamines
Which of these is a characteristic of adaptive immunity but not innate immunity?
memory
A certain cell type has existed in the blood and tissue of its vertebrate host's immune system for over 20 years. One day, it recognizes a newly arrived antigen and binds to it, subsequently initiating a secondary immune response in the body. Which of the following cell types most accurately describes this cell?
memory cell
Which of these cells is responsible for the rapidity of the secondary immune response?
memory cells
The primary reason for needing a new vaccine for influenza each year is that __________.
mutation in the influenza virus is frequent
Is this statement supported or not supported by the graph? The primary immune response takes about 28 days to reach its peak.
not supported
Is this statement supported or not supported by the graph? The primary immune response to antigen X occurred just as fast as the secondary immune response to antigen X.
not supported
Which of the following components make up a light chain of an immunoglobulin (Ig) molecule, of any class, with regions symbolized as C or V, H or L?
one C region and one V region
Lymphocytes mature in the ________. I) spleen II) thymus I) bone marrow
only II and III
The role of cytotoxic T cells is the secretion of _____, which plays a role in the _____ immune response.
perforin ... cell-mediated (Perforin causes the lysis of pathogen-infected body cells)
B cells that have been stimulated by interleukin-2 develop into _____.
plasma cells
Which of these cells produce and secrete antibodies?
plasma cells
Which of the following is least likely to help a virus avoid triggering an adaptive immune response?
producing proteins very similar to those of other viruses
Double-stranded viral DNA is incorporated into a host cell as a _____.
provirus
Within a differentiated B cell, the activity of which molecule results in the rearrangement of DNA sequences between variable regions and joining regions?
recombinase
The fact that there are about a million different antigen receptors possible in human B cells is based on __________.
recombination of the DNA segments that make up the functional receptor genes of differentiated B cells
To view the animation, click here. Then click Start on the image to start the animation. What enzyme is responsible for the process seen here?
reverse transcriptase
Clonal selection and differentiation of B cells activated by antigen exposure leads to the production of ________.
short-lived plasma cells that secrete antibodies for the antigen
The genetic material of HIV consists of _____.
single-stranded RNA
Is this statement supported or not supported by the graph? The secondary immune response is stronger than the primary immune response.
supported
What does the y-axis of this graph represent?
the antibody concentration in the blood
What does the blue line on this graph represent?
the concentration of antibodies to antigen X
What does the first blue peak (around day 17) represent?
the highest concentration of antibodies that occurs after the first exposure to antigen X
Which statement best describes an account of immunological memory?
the observation that someone who had recovered from the plague could safely care for those newly diseased
What does the second blue peak (around day 40) represent?
the peak of the secondary immune response to antigen X
Which of the following protects both the eyes and the respiratory tract against infections?
the secretion of lysozyme onto their surfaces
Which of the following should be the same in identical twins?
the set of MHC molecules produced
Cell-mediated immunity differs from humoral immunity in that __________.
they respond differently to invaders
Mucus occurs in both the respiratory and digestive tracts. Which answer best describes the main immunological function of mucus?
to physically trap pathogens
Vaccination offers protection against future exposure to pathogens because it ________.
triggers clonal expansion of lymphocytes
What is the source of a viral envelope?
host cell membrane
Which of the following are typical features of an inflammatory response?
increased activity of phagocytes in an inflamed area
A boy falls while riding his bike. A scrape on his hand almost immediately begins to bleed and becomes red, warm, and swollen. Which type of response is most consistent with these symptoms?
inflammatory response
Acidity in human sweat is part of which type of immune system?
innate immunity
An antigen __________.
is a molecule that evokes an immune response by a lymphocyte
Which of the following are molecules on mammalian cells that recognize macromolecules that are present in or on certain groups of pathogens?
toll-like receptors
An epitope associates with which part of an antigen receptor or antibody?
variable regions of a heavy chain and light chain combined
A strain of fruit fly lacks the ability to produce Dicer-2 protein will most likely be susceptible to which of the following types of infections?
viral
Which of the following statements is true?
A lymphocyte has receptors for a single antigen.
You are prescribed antibiotics for strep throat. Which of the following is true?
The drug will kill many kinds of bacteria.
