Nokea
Which pathway in the complement system is activated by immune complexes containing IgG or IgM?
- A. Alternative pathway
- B. Classical pathway
- C. Lectin pathway
- D. Terminal pathway
Correct Answer: B
Rationale: The correct answer is B: Classical pathway. This pathway is activated by immune complexes containing IgG or IgM. When these antibodies bind to antigens, they trigger the classical pathway by forming a complex that activates C1q, initiating a cascade of reactions leading to inflammation and opsonization. The alternative pathway (A) is activated by microbial surfaces, while the lectin pathway (C) is activated by mannose-binding lectin binding to carbohydrates on pathogens. The terminal pathway (D) involves the formation of the membrane attack complex.
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If a person is infected with some deadly microbes to which quick immune response is required, we need to directly inject the preformed antibodies. This type of immunisation is known as:
- A. Active Immunisation
- B. Passive immunisation
- C. Allergic immunisation
- D. No such type of immunisation exist
Correct Answer: B
Rationale: Passive immunisation involves injecting preformed antibodies to provide immediate protection against microbes. This is suitable for quick immune response in infected individuals. Active immunisation, on the other hand, stimulates the body to produce its own antibodies over time, which is not ideal for immediate protection. Allergic immunisation is unrelated to providing antibodies. There is no immunisation type of "No such type of immunisation exist."
A protective response to Leishmania parasites is most likely to occur when:
- A. Activated Th cells differentiate into Th1 effectors that secrete IL-4 required to induce secretion of appropriate antibody isotypes
- B. Activated Th cells differentiate into Th2 effectors that secrete IL-4 required to activate macrophages
- C. Activated Th cells differentiate into Th1 effectors that secrete IFNγ required to activate macrophages
- D. Either a Th1- or a Th2-mediated response occurs
Correct Answer: C
Rationale: The correct answer is C because in response to Leishmania parasites, the activation of Th cells into Th1 effectors that secrete IFNγ is crucial for activating macrophages to eliminate the intracellular parasites. IFNγ enhances the microbicidal activity of macrophages, helping to control the infection.
Choice A is incorrect because IL-4 is not required to induce the appropriate antibody response against Leishmania parasites.
Choice B is incorrect because Th2 effectors secreting IL-4 would not activate macrophages effectively against Leishmania, which is an intracellular pathogen.
Choice D is incorrect because in the case of Leishmania, a Th1-mediated response is most effective due to the need for macrophage activation by IFNγ.
Which of the following is not a function of the immune system?
- A. Protecting the body from foreign substances
- B. Producing hormones
- C. Repairing damaged tissues
- D. All of the above are functions of the immune system
Correct Answer: B
Rationale: The correct answer is B: Producing hormones. The immune system's main functions are to protect the body from foreign substances and repair damaged tissues. Producing hormones is not a direct function of the immune system. Hormone production is primarily regulated by the endocrine system, not the immune system. Therefore, option B is not a function of the immune system. Options A and C are incorrect as protecting the body from foreign substances and repairing damaged tissues are essential roles of the immune system. Option D is incorrect because not all functions listed are actually performed by the immune system.
Which of the following DNA polymerases cleaves a DNA sequence at the direction of 5' → 3'?
- A. DNA polymerase I
- B. DNA polymerase II
- C. DNA polymerase III
- D. DNA polymerase IV
Correct Answer: A
Rationale: The correct answer is A: DNA polymerase I. DNA polymerase I has both 5' to 3' polymerase activity and 5' to 3' exonuclease activity, allowing it to cleave DNA in the 5' to 3' direction. This enzyme can remove RNA primers during DNA replication by cleaving them in the 5' to 3' direction and replace them with DNA nucleotides. DNA polymerase II, III, and IV do not have the same exonuclease activity as DNA polymerase I, so they are not capable of cleaving DNA sequences in the 5' to 3' direction like DNA polymerase I.
What accurately describes passive acquired immunity (select all that apply)?
- A. Pooled gamma globulin
- B. Immunization with antigen
- C. Temporary for several months
- D. Immediate, lasting several weeks
Correct Answer: C
Rationale: Passive acquired immunity involves the transfer of antibodies from one individual to another, such as pooled gamma globulin, maternal immunoglobulins, and immediate protection that lasts for weeks to months.