Practice exam questions Flashcards
In an experiment to determine the infectious dose for a specific organism, 50% of the test subjects must develop the disease following a specific dose. This is quantified as the ID50 and is a measure of the pathogenicity of that organism. Assess the following data from an experiment involving 200 mice and determine the ID50 for the infectious agent.
Infectious Dose Living Mice Dead Mice
103 190 10
104 150 50
105 120 80
106 100 100
107 0 200
106 organisms
Which of the following is in the correct order from greatest to least phagocytic activity?
a. Neutrophils, eosinophils, macrophages
b. Neutrophils, macrophages, eosinophils
c. Eosinophils, macrophages, neutrophils
d. Macrophages, neutrophils, eosinophils
e. Macrophages, eosinophils, neutrophils
d. Macrophages, neutrophils, eosinophils
Robert Koch is credited with proving the germ theory of disease; that infectious diseases are caused by specific microorganisms. In developing a series of proofs (Koch’s Postulates), he was able to determine the causative organism of anthrax was the bacteria Bacillus anthracis. Which of the following statements does not contribute to Koch’s Postulates and the germ theory of disease?
a. The causative organism must be evidenced in each subject presenting with the disease manifestations.
b. Inoculating a healthy subject with the isolated organism must result in the reported disease manifestations.
c. The organism must be isolated, purified and characterized from an infected individual.
d. Each organism from a polymicrobial infection must be isolated and inoculated into a single host.
e. The same species of organism must be isolated from the second inoculated individual.
d. Each organism from a polymicrobial infection must be isolated and inoculated into a single host.
If an infectious disease emerged that was highly contagious and virulent, resulting in certain death with no known cure, epidemiological data would show _______.
a. a high incidence and low prevalence
b. a low incidence and high prevalence
c. both incidence and prevalence to be high
d. both incidence and prevalence to be low
a. a high incidence and low prevalence
Nowadays, HIV infection is considered a chronic disease, rather than the death sentence it was when it first emerged in the 1980s. Educational strategies to limit transmission, coupled with advances in treatment, means that compared to 1985, _______.
a. the incidence has dropped and the prevalence has increased
b. the incidence has increased and the prevalence has dropped
c. both incidence and prevalence have increased
d. both incidence and prevalence have dropped
a. the incidence has dropped and the prevalence has increased
During 2007, there were 3.6 new cases of pertussis per 100,000 susceptible individuals in the United States, part of a steady increase that has been occurring since the 1980s.
Please select the term that is illustrated by this statistic.
a. Mortality
b. Prevalence
c. Incidence
d. Epidemic rate
e. Endemic rate
c. Incidence
Cytokines are chemicals and proteins that are critical components of the immune system. Which of the following statements is incorrect regarding the function of cytokines?
a. All cytokines are synthesized to stimulate the inflammatory response; their purpose is to mediate vascular reactions and diapedesis.
b. Cytokines are secreted by a wide variety of cell types, including immune cells, epithelial and endothelial cells.
c. Cytokines play a role in both inflammatory stimulation, as well as being anti-inflammatory mediators.
d. Cytokines mediate communication between cells; they are crucial for stimulation, suppression and control of all aspects of the immune response.
a. All cytokines are synthesized to stimulate the inflammatory response; their purpose is to mediate vascular reactions and diapedesis.
Which of the following is not a mechanism employed by the human microbiota to contribute to the first line of defense?
a. It can phagocytose pathogens
b. It can lower the pH making the environment too acidic for pathogens to survive
c. It can out-compete pathogens for limited nutrients
d. It can train the immune cells to recognize antigenic markers
e. It can block potential binding sites on epithelial cells restricting adhesion, which is a necessary step for infection
a. It can phagocytose pathogens
Which statement below characterizes the complement system?
a. Complement comprises a team of blood proteins that are activated in a cascade, ultimately leading to pathogen cytolysis, inflammation and enhanced phagocytosis.
b. Complement pyrogens stimulate the hypothalamus to raise the body temperature, increasing metabolism and preventing the growth of temperature-sensitive pathogens.
c. Complement proteins bind to cell surfaces and induce changes in genetic expression, eliminating not only pathogens, but cancer cells also.
d. Complement proteins, produced by a host cell in response to viral attack, are secreted and enter neighboring cells, stimulating the production of antiviral proteins in anticipation of an invasion.
a. Complement comprises a team of blood proteins that are activated in a cascade, ultimately leading to pathogen cytolysis, inflammation and enhanced phagocytosis.
Which statement below characterizes the action of interferon?
a. Interferon, produced by a host cell in response to viral attack, is secreted and enters neighboring cells, stimulating the production of antiviral proteins in anticipation of an invasion.
b. Interferon stimulates the hypothalamus to raise the body temperature, increasing metabolism and preventing the growth of temperature-sensitive pathogens.
c. Interferon comprises a team of blood proteins that are activated in a cascade, ultimately leading to pathogen cytolysis, inflammation and enhanced phagocytosis.
d Interferon binds to cell surfaces and induces changes in genetic expression, eliminating not only pathogens, but cancer cells also.
a. Interferon, produced by a host cell in response to viral attack, is secreted and enters neighboring cells, stimulating the production of antiviral proteins in anticipation of an invasion.
B cell-receptors are similar to T cell-receptors in that ________.
a. both receptors are similar in size
b both receptors have a variable and a constant region
c. both receptors can be secreted in response to antigen
d. both receptors are comprised of four polypeptide chains
e. All of the choices reflect similarities between B cell- and T cell-receptors.
b both receptors have a variable and a constant region
The importance of clonal deletion is that ________.
a. lymphocytes with receptors that recognize self markers are eliminated to preserve immune tolerance
b. worn-out lymphocytes are destroyed to make way for new cells
c. lymphocytes that have been activated during antigen exposure are then removed when the individual recovers
d. clones of cells that have the same receptor are deleted to avoid redundancy
a. lymphocytes with receptors that recognize self markers are eliminated to preserve immune tolerance
Herd immunity involves _______.
a. maintaining a certain level of immunized individuals in a society to prevent a pathogen from circulating through the population
b. keeping bovine diseases to a minimum so they do not spread to the human population
c. encouraging individuals to work and live in close proximity to each other to prevent spread of a disease outside of a population
d. maintaining a 100% vaccination rate among farm workers to prevent the spread of zoonotic diseases
a. maintaining a certain level of immunized individuals in a society to prevent a pathogen from circulating through the population
Lymphocyte maturation involves ________.
a. hormonal signals that initiate development
b. B cells maturing in bone marrow sites
c. T cells maturing in the thymus
d. release of mature lymphocytes to begin migration to various lymphoid organs
e. All of the choices are correct.
e. All of the choices are correct.
Helper T cells ________.
a. secrete antibodies
b. function in allergic reactions
c. directly destroy target cells
d. suppress immune reactions
e. activate B cells and other T cells
e. activate B cells and other T cells
