Exam 4 Microbiology
When do helper T-cells develop into TH1 or TH2 cells?
After proliferation into a clonal population
Endotoxins are comparatively different from exotoxins, because __________. -endotoxins are not secreted proteins -exotoxins can affect sites -distant from the infection site -endotoxins are associated with more fatalities -All the listed responses are correct.
All the listed responses are correct.
Which of the complement pathways employs properdin?
Alternative pathway
A response that is uniquely directed against pathogenic Bordetella pertussis would involve what component?
Antibodies
TH2 cells produce cytokines that activate
B cells
Which domain of the A-B toxin binds to cell surface receptors on the host cell?
B domain
Which of the following are likely to be found on an MHC-I protein?
Damaged mitochondrial fragment
According to the animation, on which day does the production of IgG occur in the secondary response?
Day five
Which of the following phagocytic processes occurs last in the sequence?
Exocytosis
First line defenses have what aspect in common with each other?
First line defenses have what aspect in common with each other?
Which of the following features of Salmonella prevent it from being phagocytosed?
Flagella
How does cytolysis occur via the complement pathway?
Formation of the MAC in invading cells, killing them
What does the plasma membrane of a phagocyte attach to on a microorganism?
Glycoproteins
Which part of the adaptive immune response involves B cells?
Humoral
Which of the following enzymes breaks down the "glue" that holds cells together?
Hyaluronidase
Why is vasodilation important to tissue repair?
It allows for an increased delivery of oxygen, nutrients, and phagocytes to the site of damage.
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.
An inflammatory response would result from which of the following?
Jellyfish sting
Endotoxins are also known as
Lipid A
Where is the site of Shigella attachment in the host?
M cells
Which proteins on the antigen-presenting cell are recognized by the helper T-cell?
MHC proteins
Which cells are involved in a secondary response?
Memory B cells and plasma cells
A researcher wanted to determine the LD50 (lethal dose that kills 50% of the infected hosts) for a newly isolated bacterial pathogen. Mice were inoculated with diluted cultures containing between 101 and 107 cells. After two days, all of the mice had died EXCEPT for the uninoculated controls. Which of the following is the most likely explanation?
This pathogen is highly virulent in mice.
What is the function of inflammation in response to a burn from a hot iron?
To repair the damaged tissue
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.
Which of the following microorganisms actually grows inside the macrophage?
Tuberculosis bacterium
When would endotoxins be released from a bacterial cell?
When the cell dies
Based on the animation, which of the following is cleaved by C1?
C2 and C4
Based on the animation, which of the following is responsible for cleaving C3?
C2aC4b
In the classical pathway, which of the following directly activates cellular responses?
C3a, C5a, and C5bC6C7
Based on the animation, which of the complement proteins can directly bind to the surface of a bacterial cell?
C3b
Which complement protein is used as an opsonin?
C3b
How can capsules enable bacteria to evade the immune system?
Capsules block the complement biding sites on the surface of the pathogen
Which of the following can release histamines?
Cells from damaged tissues and the complement pathway
What complement result involves the use of phagocytes?
Chemotaxis and opsonization
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
What would a virally infected skin epithelial cell have on its cell surface?
Class I MHC with skin cell antigens
Which microorganism requires the low pH inside a phagolysosome in order to reproduce?
Coxiella burnetii
If a person could not form C2, which result of complement would be affected?
Cytolysis, chemotaxis, inflammation, and opsonization
All AB toxins have which of the following?
two subunits
Certain traits that allow pathogens to create infection and cause disease are termed
virulence factors
If a person lacked the ability to form C5, what direct result of complement could still occur?
Opsonization
Which statement correctly identifies an activity of the innate immune system?
Phagocytes can recognize the LPS layer of any gram-negative cell.
Which structure do antigen presenting cells utilize to directly help them present bacterial antigens?
Phagolysosome
What cellular macromolecules make up the complement pathway?
Protein
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.
What is the etiologic agent of typhoid?
Salmonella
Which of the following virulence factors would be found in Staphylococcus aureus?
Staphylokinase
Which of the following microorganisms use M protein to avoid destruction of a phagocyte?
Streptococcus pyogenes
How are superantigens different from other types of exotoxins?
Superantigens cause an overstimulation of the host immune system
Which receptor on the helper T-cell recognizes the specific antigen from an antigen-presenting cell?
TCR
Natural killer cells are activated by
Th1 cells
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.
For several months a graduate student has been working with a pure culture of a suspected bacterial pathogen in an attempt to determine whether it causes disease in various animal models. She had initially found that the organism was highly virulent in mice, but when she attempted to replicate her early experiments weeks later, all of the new experimentally infected mice survived. The student has brought her surprising findings to the lab's weekly research meeting. What advice could you give her?
The bacterial strain may have become attenuated.
Where are the complement proteins found in the body?
The blood serum
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.
Virulence factors that enhance invasiveness of a pathogen can include _________
collagenase coagulasee xotoxins
Clostridium perfringens causes gas gangrene, a serious infection of the muscle tissues that can lead to amputation. Clostridium are Gram-positive endospore-formers and obligate anaerobes that are killed when exposed to oxygen. Which of the following virulence factors would be most helpful to this organism in establishing an infection?
collagenase, an enzyme that destroys collagen, which is a major protein of connective tissues
Obligate anaerobes are likely to be found in the __________.
colon
The colon has been described as a living fermentation vessel. Which type of culture system would it most resemble?
continuous culture
An exotoxin that has the ability to kill or damage host cells is referred to as a(n)
cytotoxin.
The diphtheria exotoxin is an A-B toxin that __________.
is found only in Corynebacterium diphtheriae cells that have been infected with lysogenic bacteriophage β
A pharmaceutical company that uses the Limulus amoebocyte lysate (LAL) assay to test water that is used to make sterile saline for intravenous administration is trying to detect small amounts of which of the following?
endotoxin
C. difficile infections are on the rise, both in elderly hospitalized patients receiving antibiotics and in younger populations having no previous contact either with a hospital environment or antibiotics. What is the most effective treatment for chronic C. difficile infections?
fecal transplants from a healthy donor
Which of the following would be the first sign of an infection that resulted in the release of endotoxin?
fever
How is Streptococcus pneumoniae able to avoid destruction by a phagocyte?
heir capsules make them "slippery" to phagocytes.
Antibodies are a part of which type of immunity?
humoral
Which of the following is another term for antibodies?
immunoglobins
Which of the following is most likely to cause disease?
injection of 105 cells of a highly virulent bacterial species into a mouse
Antigen processing and presentation
is a way for a cell to give information about its activities.
Helicobacter pylori is a bacterium found in the stomachs of roughly half of the human population. It is considered to be a pathogen because __________.
it can cause chronic inflammation
Why is a release of endotoxin into the bloodstream potentially deadly?
it can lower blood pressure and cause the patient to go into shock.
Complement-coated pathogens can be __________.
lysed or opsonized as a result of complement binding, depending on the type of cell
Recent evidence shows that signals from the extracellular matrix (ECM) can regulate the expression of genes in the cell nucleus. A likely mechanism is that
mechanical signals of the ECM can alter the cytoskeleton, which can alter intracellular signalling.
A decrease in response time and increased concentration of antibody production after the primary immune response is due to __________.
memory B cells
Cytochalasin D is a drug that prevents actin polymerization. A cell treated with cytochalasin D will still be able to
move vesicles around the cell.
A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)
neurotoxin.
What must every pathogen do to cause disease? -invade host tissues -produce exotoxins -adhere to host tissue -none of these
none of these
One advantage of a monogastric digestive system is that __________.
nutrients are easily accessible to the microbes that aid in digestion and vitamin production
The ability to cause disease is called _____.
pathogenicity
Phagocytes recognize pathogens through their use of __________.
pattern recognition receptors
which of the following is an important virulence factor for dental caries?
polysaccharide adhesion
Secondary lymphoid organs include the __________.
spleen
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.
Measles viruses are capable of inactivating host defenses by
suppressing the immune system.
Karen stepped on a rusty nail while walking her dog barefoot. She needs to be treated to prevent damage by which exotoxin?
tetanus exotoxin
Antibodies from cellular immune responses are used in
the classical pathway.
Which of the complement pathways was discovered first?
the classical pathway.
Phagocytosis is defined as
the ingestion of solid material by a eukaryotic cell.
Diapedesis is
the migration of phagocytes through blood vessels to the site of tissue damage.
Both the innate and adaptive defenses of the immune system work to prevent
the penetration and colonization by pathogens, and the diseases they cause.
Meningitis and gonorrhea are caused by
Neisseria species
Which of the following is an example of a barrier defense that forms part of the innate immunity of vertebrates?
Acidity in the stomach kills many microbes.
Where do Salmonella pathogens grow and replicate in the infected host?
Inside phagocytes
What are leukocidins?
Molecules that are capable of destroying phagocytes
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.
What is a phagolysosome?
The structure that results from the fusion of a phagosome and a lysosome.
When a child begins to get its first teeth, what happens to the microbiota in the oral cavity?
The teeth are rapidly colonized by anaerobes, in particular Streptococcus, that are specifically adapted to growth in biofilms on the surfaces of the teeth.
Which of the following are functions of lectins?
They act as opsonins for phagocytosis, they attach to carbohydrates on some bacterial and viral surfaces, and they activate C2 and C4.
What direct effect do histamines and leukotrienes have on capillaries?
They allow capillary walls to open and become leaky.
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.
Neutrophils are the most abundant phagocytic cells. How do they differ from other phagocytic cells?
They are common in pus and at the site of acute inflammation
The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures?
They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell.
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.
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.
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.
What is the role of opsonins?
They create "handles" that make it easier for the pseudopods of phagocytes to attach to the microbe invader.
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.
An anamnestic response is
another name for secondary response.
Which of the following is similar to lymph?
blood plasma without red blood cells
Which of the following tissues is myeloid?
bone marrow
A patient admitted to the hospital with muscle weakness and paralysis is put on a ventilator because of breathing difficulties. It is determined that the symptoms are the result of a bacterial exotoxin. Which of the following is the most likely source of this toxin?
canned food
The process by which a phagocyte moves toward a chemical signal at the site of an infection is called
chemotaxis.
Pus is comprised of
dead phagocytes
