Nokea
All of the following are true with respect to IgM antibodies EXCEPT which one
- A. they fix complement
- B. they occur on the surface of lymphocytes
- C. they predominate in the primary response to antigen
- D. mediate allergic reactions
Correct Answer: D
Rationale: The correct answer is D. IgM antibodies do not mediate allergic reactions. IgE antibodies are responsible for allergic reactions. IgM antibodies fix complement, occur on the surface of lymphocytes, and predominate in the primary response to antigens. IgM is the first antibody produced in response to an infection, playing a key role in the activation of the complement system. IgM antibodies are mainly found in the blood and lymphatic system, not on the surface of lymphocytes. IgE antibodies are the primary mediators of allergic reactions by triggering the release of histamine and other inflammatory molecules.
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Which of the following is NOT true concerned with Leishmania
- A. It is a unicellular parasite
- B. Proliferates inside phagocytic cells
- C. Transmitted by sand flies
- D. Protection is mainly mediated by IgE
Correct Answer: D
Rationale: The correct answer is D because protection against Leishmania is mainly mediated by cell-mediated immune responses, not IgE antibodies. IgE is not typically involved in protection against intracellular parasites like Leishmania. A: Leishmania is indeed a unicellular parasite. B: Leishmania proliferates inside phagocytic cells, particularly macrophages. C: Leishmania is transmitted by sand flies during blood meals.
Identify the following types of cells that do HIV preferentially infect.
- A. Memory cells
- B. Helper T cells
- C. Cytotoxic T cells
- D. Natural killer cells
Correct Answer: B
Rationale: The correct answer is B: Helper T cells. HIV preferentially infects Helper T cells because they express the CD4 receptor, which serves as the primary binding site for the virus. Once infected, HIV impairs the Helper T cells' function, leading to immune system dysfunction. Memory cells (A), Cytotoxic T cells (C), and Natural killer cells (D) are not the primary targets of HIV infection as they do not express the CD4 receptor necessary for HIV entry and replication. Helper T cells are crucial for orchestrating immune responses, making them the primary target for HIV infection.
What is required for sensitization in contact hypersensitivity?
- A. Antigen-antibody complex formation
- B. T cell presentation of a hapten-modified antigen
- C. Mast cell degranulation
- D. Cytokine suppression
Correct Answer: B
Rationale: The correct answer is B because sensitization in contact hypersensitivity requires T cell presentation of a hapten-modified antigen. This process activates T cells, leading to immune response. Antigen-antibody complex formation (A) is more related to immune responses in humoral immunity. Mast cell degranulation (C) is associated with allergic reactions, not contact hypersensitivity. Cytokine suppression (D) would hinder, not promote, the immune response needed for sensitization in contact hypersensitivity.
Which group(s) of microorganisms is (are) thought to be the oldest living organisms?
- A. eukaryotes
- B. heterotrophic prokaryotes
- C. Archaea
- D. viruses
Correct Answer: C
Rationale: The correct answer is C: Archaea. Archaea are thought to be the oldest living organisms due to their unique characteristics and genetic similarities to the earliest forms of life. They are known for thriving in extreme environments, resembling conditions on early Earth. Other choices are incorrect because eukaryotes are more complex and evolved later, heterotrophic prokaryotes came after autotrophic prokaryotes, and viruses are not considered living organisms.
Prophylactic measures that are routinely used as early as possible in HIV infection to prevent opportunistic and debilitating secondary problems include administration of
- A. isoniazid (INH) to prevent tuberculosis
- B. trimethoprim/sulfamethoxazole (TMP/SMX) for toxoplasmosis
- C. vaccines for pneumococcal pneumonia, influenza, and hepatitis A and B
- D. varicella-zoster immune globulin (VZIG) to prevent chickenpox or shingles
Correct Answer: C
Rationale: Vaccination protects against preventable infections that can become severe in immunocompromised individuals.