Exam 3 Flashcards
Endotoxins are also known as
Lipid A.
When would endotoxins be released from a bacterial cell?
When the cell dies
Which of the following would be the first sign of an infection that resulted in the release of endotoxin?
Fever
Why is a release of endotoxin into the bloodstream potentially deadly?
It can lower blood pressure and cause the patient to go into shock.
An exotoxin that has the ability to kill or damage host cells is referred to as a(n)
cytotoxin.
Which domain of the A-B toxin binds to cell surface receptors on the host cell?
B domain
How are superantigens different from other types of exotoxins?
Superantigens cause an overstimulation of the host immune system.
A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)
superantigen
A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)
neurotoxin
In mice, the LD50 for staphylococcal enterotoxin is 1350 ng/kg, and the LD50 for Shiga toxin is 250 ng/kg. Which of the following statements is true?
Shiga toxin is more lethal than staphylococcal enterotoxin.
Which of the following would be an example of an infection initiated via the parenteral route?
An individual contracts hepatitis B from an accidental stick with a contaminated needle.
Which of the following statements about adherence is true?
Most bacterial adhesins are glycoproteins or lipoproteins.
Which disease would be potentially propagated in an environment without functional plumbing and in which drinking water is contaminated with sewage?
cholera
Which type of bacterial enzyme helps spread Streptococcus pyogenes by digesting blood clots?
fibrinolysin
Which of the following features of Salmonella prevent it from being phagocytosed?
Flagella
Where do Salmonella pathogens grow and replicate in the infected host?
Inside phagocytes
Where is the site of Shigella attachment in the host?
M cells
How do Shigella cells move between host cells?
They can polymerize actin molecules from the epithelial cells into tail-like structures that propel them from one cell to another.
What is the etiologic agent of typhoid?
Salmonella
How are immune cells able to detect foreign pathogens?
They are able to detect structures on the surfaces of foreign cells that are not found in the host.
How does a capsule help certain bacteria evade detection by the immune system?
The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign.
Which of the following microorganisms actually grows inside the macrophage?
Tuberculosis bacterium
How does the protozoan Trypanosoma evade detection by the immune system?
It can change the surface antigens frequently, preventing the immune system from tracking it.
Certain traits that allow pathogens to create infection and cause disease are termed
virulence factors.
Which of the following enzymes breaks down the “glue” that holds cells together?
Hyaluronidase
Which of the following virulence factors would be found in Staphylococcus aureus?
Staphylokinase
How do fibrinolysins enhance a pathogen’s virulence?
They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.
What are leukocidins?
Molecules that are capable of destroying phagocytes
Measles viruses are capable of inactivating host defenses by
suppressing the immune system.
Meningitis and gonorrhea are caused by
Neisseria species.
How do superantigens enable pathogens to hide from the immune system if they actually stimulate the immune system?
They cause the immune system to produce an exaggerated response, distracting it from the actual pathogen.
How can capsules enable bacteria to evade the immune system?
Capsules block the complement biding sites on the surface of the pathogen.
Which statement regarding endotoxins is true?
One consequence of endotoxins is the activation of blood-clotting proteins
In which of the following cases would the Limulus amebocyte lysate (LAL) assay be used?
to ensure that a sterilized medical device is free of endotoxin
Which of the following toxins and descriptions do NOT match?
Vibrio enterotoxin: a superantigen that destroys epithelial cells
Which of the following statements about lysogenic conversion is true?
Exotoxin production by bacteria is frequently the result of a lysogenic infection.
What do hyaluronidase and kinase have in common?
They are both enzymes involved in evading host defense.
According to your Concept Map, which of the following organisms exhibits antigenic variation?
N. gonorrheae
Which of the following virulence factors could directly prevent phagocytosis and/or phagocytic degradation?
waxy lipids
M proteins
capsules
Which of the following is NOT a cytopathic effect (CPE) of viruses?
chromosomal changes in the host cell
the formation of a syncytium
formation of inclusion bodies
All of the listed choices are possible cytopathic effects of viruses.
Julie is preparing vegetables for dinner and accidentally cuts her finger. She washes it with soap and water before covering it with a bandage. A short while later, Julie notices that her finger is red, swollen, warm to the touch, and very painful. Which of the following describes the process going on in Julie’s finger?
inflammation
Inflammation is part of the second line of defense that is activated when the first line of defense is breached. Julie’s first-line defenses were damaged when her injury occurred. Which of the following represents the first line of defense?
skin and mucous membranes
As mentioned previously, the second line of defense is activated when the first line of defense fails. In Part A, you identified one of these defenses as inflammation, which occurs when the body responds to a foreign antigen and increases fluid accumulation in a specific area. An added benefit of this excess fluid is that it also brings immune cells to the area to aid clearance of foreign antigens. In Julie’s situation, that added fluid would bring immune cells to prevent any microbial infections that could be caused if microbes were introduced when she cut her finger. Which of the following cell types is NOT part of the second line of defense?
plasma cells
The adaptive immune response, or third line of defense, is activated when the first and second lines of defense do not succeed in containing an infection. It is adaptive because the cells in this part of the immune system are capable of responding to specific pathogens. Another important feature of the third line is the ability of these cells to create memory cells. Why are memory cells an important product of an immune response?
Memory cells allow subsequent immune responses against the same antigen to occur more strongly and more quickly.
Which non-specific defense mechanism is mismatched with its associated body structure or body fluid?
mucociliary escalator intestines
Which group contains ONLY innate physical defenses?
intact skin, tears, ciliary escalator
What direct effect do histamines and leukotrienes have on capillaries?
They allow capillary walls to open and become leaky.
Diapedesis is
the migration of phagocytes through blood vessels to the site of tissue damage.
Why is vasodilation important to tissue repair?
It allows for an increased delivery of oxygen, nutrients, and phagocytes to the site of damage.
Pus is comprised of
dead phagocytes.
Which of the following can release histamines?
Cells from damaged tissues and the complement pathway
All of the following pertain to fever EXCEPT that it
accelerates microbial growth by increasing iron absorption from the digestive tract.
The antimicrobial effects of AMPs include all of the following EXCEPT
inhibition of phagocytosis.
Which of the following statements about innate immunity is true?
Innate immunity is present at birth.
Mucous membranes are a part of
innate defense.
According to the animation, B cells interact directly with
helper T cells.
Which of the following defense systems would be involved in eliminating virally-infected cells?
T lymphocytes
According to the animation, antibodies interact with which innate defenses?
Phagocytosis and the complement system
Which cells directly attack abnormal cells in the body?
Cytotoxic T cells
If one is examining a blood smear from a patient with a parasitic worm infection, which of the following leukocytes would be found in increased numbers?
eosinophils
A response that is uniquely directed against pathogenic Bordetella pertussis would involve what component?
Antibodies
First line defenses have what aspect in common with each other?
They are physical barriers against invading pathogens.
Both the innate and adaptive defenses of the immune system work to prevent
the penetration and colonization by pathogens, and the diseases they cause.
If a new bacterial pathogen entered a human body through an accidental needle stick, the first cell that would try to kill the pathogen would likely be
a phagocyte.
Which statement regarding the lymphatic system is true?
Lymphatic capillaries possess one-way valves. These valves permit the uptake of fluid from the body but do not allow the fluid to flow back out of the capillaries into the intracellular spaces.
What does the plasma membrane of a phagocyte attach to on a microorganism?
Glycoproteins
The process by which a phagocyte moves toward a chemical signal at the site of an infection is called
chemotaxis.
Which of the following phagocytic processes occurs last in the sequence?
Exocytosis
What is the role of opsonins?
They create “handles” that make it easier for the pseudopods of phagocytes to attach to the microbe invader.
What is a phagolysosome?
The structure that results from the fusion of a phagosome and a lysosome.
Phagocytosis is defined as
the ingestion of solid material by a eukaryotic cell.
How is phagocytosis in the immune system different from protozoan phagocytosis?
Protozoan phagocytosis is used for feeding; phagocytosis by immune cells is used to fight infection.
How is Streptococcus pneumoniae able to avoid destruction by a phagocyte?
Their capsules make them “slippery” to phagocytes.
Which microorganism requires the low pH inside a phagolysosome in order to reproduce?
Coxiella burnetii
Which of the following microorganisms use M protein to avoid destruction of a phagocyte?
Streptococcus pyogenes
Mycobacterium tuberculosis is an intracellular pathogen of humans. After being ingested by a macrophage, it prevents formation of the ___________ by preventing fusion of the phagosome with the ___________________.
phagolysosome, lysosome
In which intracellular compartment would you expect most of the digestive enzymes involved in pathogen destruction to be found?
lysosome
In macrophages and dendritic cells (so-called antigen-presenting cells) some small parts of the phagocytosed particle are presented to other cells of the immune system. If you were to draw an arrow leading to “antigen presentation” as described above, from which word would it extend?
digestion
Which of the following statements concerning phagocytosis is true?
Bacteria are digested when the phagosome fuses with a lysosome.
__________ is/are always present in an individual’s blood. However, in the absence of infection, it is in an inactive form
Kinins
An inflammatory response would result from which of the following?
Jellyfish sting
If a person turns their ankle, how would one determine if damage to the tissue in the ankle has occurred?
The ankle is red, swollen, and warm to the touch.
What is the function of inflammation in response to a burn from a hot iron?
To repair the damaged tissue
You note that the body temperature of one of your patients is starting to increase. As a result, you can infer that all of the following may be occurring in this patient EXCEPT __________.
dilation of blood vessels
One of your first ideas is to look at probiotics to enhance the host’s normal microbiota. The use of probiotics to stimulate the normal intestinal microbiota and promote general health has gained increasing popularity in recent years. There are several ways in which our normal microbiota protects us from infection. Which of the mechanisms below is not a protective mechanism of our normal microbiota?
Normal microbiota spreading to locations where they are not normally found to prevent colonization from pathogens.
The complement cascade involves a series of proteins that circulate in the blood. There are three pathways that lead to activation of the complement cascade–classical, alternative, and lectin. Your goal is to enhance the immediate response to bacterial infection. With this goal in mind, why might you choose to target the lectin or alternative pathways rather than the classical?
Neither pathway relies on antibodies.
Targeting inflammation as an infection control mechanism is a double-edged sword. On one side, inflammation evolved to help eliminate and/or contain pathogens. On the other, too great of an inflammatory response will lead to tissue destruction and lasting damage. You decide to focus on the process of margination during inflammation. Predict the most likely outcome of enhancing margination.
enhanced phagocytosis
Mucous membranes are a part of
innate defense.
Which of the following defense systems would be involved in eliminating virally-infected cells?
T lymphocytes
According to the animation, antibodies interact with which innate defenses?
Phagocytosis and the complement system
Which cells directly attack abnormal cells in the body?
Cytotoxic T cells
What is the role of helper T cells in the adaptive immune response?
Helper T cells activate B cells and cytotoxic T lymphocytes to kill infected host cells.
What is meant by the clonal expansion of a B cell?
An activated B cell divides into cells that give rise to memory B cells and plasma cells
The student who caught the cold caused by this specific Rhinovirus was exposed to the exact same Rhinovirus 18 months later. What component of the immune system will protect her from getting the same cold again?
Memory B cells
Which of the following is NOT a step used by cytotoxic T cells to kill infected host cells?
Recognition of infected host cell using its CD4 glycoprotein
Which pair of molecules do NOT directly interact with one another?
BCR and TCR
Which of the following is NOT a step that ultimately leads to antibody production?
Activation of cytotoxic T cells by helper T cells
A person who has AIDS contracts rare and often life-threatening infections because their helper T cell count is so low. Which of the following components of the immune response still respond to antigen despite the low helper T cell count?
Clonal selection of B cells
Which of the following statements is true?
Adaptive defenses include both humoral and cellular immunity.
Phagocytosis is a process for engulfing large particles (>1μm). Which feature of antibodies will help to make particles larger, therefore enhancing phagocytosis?
agglutination
The flu virus mutates fairly frequently. Its adhesive proteins change such that we have different “strains” of influenza each year. When a particular flu virus mutates such that its adhesive proteins change, which function of antibodies is disrupted?
neutralization
__________________ stimulated with ___________ differentiate into __________, which secrete antibodies into the bloodstream.
B-cells, antigen, plasma cells
Antigen processing and presentation
is a way for a cell to give information about its activities.
Why would a body cell that is not a phagocyte need to present antigens?
Non-phagocytic body cells can become infected with a virus.
How do phagocytes communicate to other cells what they have captured?
They present antigens from engulfed foreign cells.
Which of the following best characterizes clonal selection?
The production of identical B cells producing the same antibody
What is produced by the process of clonal expansion?
Plasma cells and memory B cells
An antigen that is potent enough to activate a B cell on its own is known as
T-independent antigens.
Based on the animation, T cells recognized the antigen displayed by what protein of the B cell?
MHC
How can a sufficient humoral immune response occur if a plasma cell only lives for a few days?
Each plasma cell can produce up to 2000 antibodies every second.
Which receptor on the helper T-cell recognizes the specific antigen from an antigen-presenting cell?
TCR
TH2 cells produce cytokines that activate
B cells.
Which proteins on the antigen-presenting cell are recognized by the helper T-cell?
MHC proteins
When do helper T-cells develop into TH1 or TH2 cells?
After proliferation into a clonal population
Natural killer cells are activated by
TH1 cells.
What is apoptosis?
The process of programmed cell death.
What is the function of the CD8 receptor?
Bind to MHC molecules
What is the fate of activated cytotoxic T-cells?
They proliferate into a clone of cells specific to the same antigen; some of these cells then differentiate into long-lived memory T-cells, while others mature to attack infected cells.
Which molecule triggers apoptosis?
Granzyme
Which event happens first during cytotoxic T-cell activation?
CD8 binds to MHC molecules of infected cells
Which of the following statements concerning cellular immunity is FALSE?
Cellular immunity involves cells that recognize antigens and make specific antibodies against them
The primary immune response involves
a slow rise in the concentration of antibodies, followed by a gradual decline.
According to the animation, for approximately how many days is IgG present in the serum?
Ten days
According to the animation, on what day does IgM first appear?
Day five
Which cytokines are believed to contribute to autoimmune disease, such as rheumatoid arthritis?
tumor necrosis factor (TNF)
Which immunoglobulin class, found in blood, lymph, and the intestine, can cross the placenta and help to protect a fetus?
IgG
If a patient has been exposed to an antigen for the first time, which class of immunoglobulin appears first?
IgM
What is the correct sequence of events for activation of a B cell by a T-dependent antigen?
(1) Immunoglobulin receptors on the B cell recognize and bind the antigen. (2) An antigen fragment in complex with MHC class 2 is displayed on the B cell’s surface. (3) The MHC-antigen complex binds a receptor on a TH cell. (4) The TH cell secretes cytokines that activate the B cell.
Where are MHC molecules located on a cell?
On the surface of the cell
What is a feature of the small fragments presented by MHC-I proteins?
They are small peptides, roughly 8-10 amino acids long.
Which organelle assists directly with the presentation of MHC-I antigens?
The endoplasmic reticulum
When does MHC-II loading occur?
During the fusion of vesicles containing MHC-II proteins with vesicles containing digested pathogens
Which of the cells listed below can present antigens on Class II MHC proteins?
Macrophages
Which type of cell directly attacks infected cells?
Cytotoxic T-cells
Immune cells that secrete cytokines and activate other immune cells are:
Helper T-cells
HIV directly infects T-cells. Why is this problematic for cell-mediated immunity?
Cytotoxic T-cells begin to attack the virally infected T-cells, reducing the number of T-cells in the body.
How do helper T-cells and cytotoxic T-cells work together?
Helper T-cells produce cytokines to activate other cells of the immune system.
Which of the following statements concerning antigen-presenting cells is true?
They are involved in activating T cells.
Which type of T cell is involved in activating macrophages and stimulating development of cytotoxic T cells?
TH1 cells
Which structure do antigen presenting cells utilize to directly help them present bacterial antigens?
Phagolysosome
Which of the following are likely to be found on an MHC-I protein?
Damaged mitochondrial fragment
What would a virally infected skin epithelial cell have on its cell surface?
Class I MHC with skin cell antigens
Which of the following would you likely see on the surface of a human dendritic cell following phagocytosis of a bacterium?
Class I MHC with dendritic cell antigens and Class II MHC with engulfed bacteria
Tom has a genetic disorder in which he does not synthesize class I MHC proteins or functional NK cells. Which of the following statements would be true for Tom?
Tom would not be able to destroy virally-infected cells.
Consider a helminthic infection in which an individual is colonized by a parasitic worm. The worm is too big to be engulfed by a phagocytic cell. How does the immune system respond?
The worm gets coated with antibodies, which activate other cells in the immune system to secrete chemicals that kill it.
Which of the following statements concerning immunological memory is true?
The memory response is due to production of long-lived cells that can respond very rapidly upon second exposure.
Which part of the adaptive immune response involves B cells?
Humoral
Antibodies are a part of which type of immunity?
Humoral
Which cells are involved in a secondary response?
Memory B cells and plasma cells
How is the secondary response different from the primary response in terms of antibody concentration in the blood?
The secondary response is faster and produces more antibodies than the primary response.
According to the animation, on which day does the production of IgG occur in the secondary response?
Day five
An anamnestic response is
another name for secondary response.
An individual may be exposed to a pathogen and become infected without actually getting sick. This is known as a subclinical infection. Even in subclinical infections, the individual’s adaptive immune system can generate memory for the pathogen. What type of adaptive immunity is this?
naturally acquired active immunity
In designing your vaccine, you will need to choose an antigen or antigens to stimulate the adaptive response. All antigens are not created equal–there are certain characteristics that make more effective antigens. Which of the following best describes why molecules such as glycoproteins are more effective antigens compared to molecules such as starch?
Glycoproteins contain a variety of shapes and subunits that contribute to the overall complexity of the molecule.
During the adaptive response, the MHC molecules are responsible for presenting an antigen to T cells. The two types of MHC (MHCI and MHCII) have specific roles during the response. Which of the following most accurately describes the characteristics of MHCII molecules in mounting the antibody response?
found on APC, present exogenous antigens, activate T helper cells
There are a variety of lymphocytes involved in the adaptive response, each with a specific function. One of the subsets of cells essential in the adaptive response is T helper cells. Choose the answer that most accurately describes the role of T helper cells in mounting the antibody response.
T helper cells aid the antibody response by binding to the B cell MHCII/protein complex and secreting cytokines like IL-4
