A cell infected by viruses may die due to the actions of interferons. The same result would occur WITHOUT interferon-any cell infected by a virus would die directly from the virus.
Is there any apparent benefit to the host organism from the interferon action?
A. No-interferon is just an evolutionary leftover from a much earlier form of antiviral activity. It has no function now.
B.
Yes-when the interferon acts on a virally infected cell, it shuts down protein production (which shuts down virus replication). Without interferon, virus will kill the cell eventually, but only after it has replicated many times over. Interferons may kill the host cell, but they will also prevent it from being used to replicate virus.
C. Yes-by killing host cells, you limit the number of cells that are available targets for viral infection. This is a good way of preventing viral infection.
D. No-viruses will replicate in cells regardless of the effects of interferons, so their action of killing the cell has no benefit to the host organism during the infection process.
Syphilis was once treated by intentionally infecting the patient with the parasite that causes malaria, a disease characterized by repeated bouts of fever, shaking, and chills.
Why might this treatment cure syphilis?
A. Malaria parasites produce strong antibacterial compounds (since they're eukaryotic in nature-they are trying to eliminate their competition for resources). This helps to eliminate ALL bacteria in and on the human body for a short period of time.
B.
Malaria parasites track down and feed upon ALL bacterial cells in the human body as a part of their life cycle. This makes them a natural antibiotic of sorts, and highly effective at clearing the bacterial infection of syphilis.
C. One of the side effects of malarial infection is a massive overproduction of macrophages-so many that they become the dominant cell type in the blood (even over red blood cells). This drives up the ability to ingest and destroy any microbe, including the bacterium that causes syphilis.
D. The effect of driving up the body temperature for periods of time can shut down the temperature-sensitive replication of the bacterium that causes syphilis. This gives the immune system time to eliminate it properly.
A physician is attempting new therapies for HIV patients who are suffering from an impaired immune response. He decides to try using a recombinant form of colony-stimulating factor cytokine (CSF). Why?
A. CSF is a strong inducer of antiviral activities in our cells, and may help our immune system fight off the effects of HIV for a longer period of time.
B. CSF will hyperstimulate the activities of the macrophages, leading to ingestion and destruction of HIV-infected cells.
C.
CSF will help to stimulate the production of new lymphocytes-the very cells that are infected and depleted during an HIV infection. This may help to keep the patients' immune responses normal for a longer period of time before they succumb to full-blown AIDS.
D. CSF will drive up the production of lactoferrin, a strong antiviral compound produced in our mucus membrane secretions.
Smoking impairs the ciliated cells of the middle portion of the respiratory tract. Many analgesic drugs (painkillers) impair peristalsis (the churning motion of the digestive tract).
The result of either of these activities leads to an increased risk of infection in their respective areas. Why?
A. The actions of the cells in these areas help to propel pathogens out of the area, serving as a part of the physical barrier system. When they are impaired/slowed, bacteria and other pathogens have an easier time adhering to the tissues in the area and causing an infection.
B. Ciliated cells also line the digestive tract, and these cells secrete strong natural antibacterial compounds. When they are impaired, bacteria can more easily infect these areas.
C. Chemicals in cigarette smoke and the chemicals in painkillers impair our immune systems, making us generally more predisposed to infections (regardless of the tissue area).
D. Chemicals in cigarette smoke and the chemicals in painkillers impair the ability of our immune system cells to move into areas that are infected. As such, they can't perform their job of eliminating microbes as well as they should and infections result more easily.
Toll-like receptors (TLRs) bind molecules on pathogens. Why is this helpful to the immune response?
A. It provides a highly specific response to very small and highly unique areas on an individual pathogenic microbe, providing the most specific and selective response possible.
B. It provides a general response to broad categories of molecules/cells that should NOT be in our system, as we don't have these molecules on our own cells.
C. These secreted molecules help bind pathogens and then direct them to receptors on the immune system cells that are best capable of eliminating them from our systems. TLRs are delivery mechanisms for the immune responses.
D. TLRs are capable of directly lysing (destroying) the microbes, helping our immune responses by eliminating pathogens.
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