Nokea
What underpins most functions of the immune system?
- A. Secondary lymphoid tissues
- B. Haematopoietic stem cells in the bone marrow
- C. Mucosal immune system activity
- D. Rapid cytokine suppression
Correct Answer: B
Rationale: The correct answer is B: Haematopoietic stem cells in the bone marrow. These cells are responsible for generating all immune cells, including lymphocytes, macrophages, and dendritic cells. They continuously replenish the immune system, allowing for proper immune function. Secondary lymphoid tissues (choice A) play a role in immune responses but are not the primary underpinning. Mucosal immune system activity (choice C) is important for defense at mucosal surfaces but is not the foundation of immune function. Rapid cytokine suppression (choice D) is a regulatory mechanism, not the fundamental basis of immune system functions.
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Which characteristics describe Pneumocystis jiroveci infection, an opportunistic disease that can be associated with HIV?
- A. May cause fungal meningitis
- B. Diagnosed by lymph node biopsy
- C. Pneumonia with dry, nonproductive cough
- D. Viral retinitis, stomatitis, esophagitis, gastritis, or colitis
Correct Answer: C
Rationale: Pneumocystis jiroveci pneumonia typically presents with a dry, nonproductive cough, shortness of breath, and fever.
Molecules that are considered members of the 'immunoglobulin superfamily':
- A. Contain one or more protein domains with a compact barrel structure
- B. Are always lymphocyte antigen receptors
- C. Are highly unstable relative to other proteins
- D. All of the above
Correct Answer: A
Rationale: The correct answer is A because molecules in the immunoglobulin superfamily typically contain one or more protein domains with a compact barrel structure. This structure is characteristic of immunoglobulin-like domains found in proteins involved in immune responses. Choice B is incorrect because not all members of the immunoglobulin superfamily are lymphocyte antigen receptors. Choice C is incorrect as these molecules are not necessarily highly unstable compared to other proteins. Therefore, the correct answer is A as it accurately describes a common structural feature of molecules in the immunoglobulin superfamily.
Which of the following statements about M cells is incorrect?
- A. M cells are found in Peyer's patches in the small intestine
- B. M cells are specialized epithelial cells
- C. M' stands for microfold as these cells show small folds on their luminal side rather than microvilli
- D. They specialize in the transport by transcytosis of IgA from the lamina propria (the tissue immediately below the gut lining) into the intestinal lumen
Correct Answer: D
Rationale: The correct answer is D because M cells do not transport IgA from the lamina propria into the intestinal lumen. Instead, they transport antigens and pathogens from the gut lumen to underlying immune cells. Choice A is correct as M cells are found in Peyer's patches. Choice B is correct as M cells are specialized epithelial cells. Choice C is incorrect as M cells have microfolds on their luminal side, not microvilli.
In the 1960s, smallpox was endemic:
- A. In many developing countries
- B. In North America
- C. In England
- D. Globally
Correct Answer: A
Rationale: The correct answer is A: In many developing countries. Smallpox was indeed endemic in many developing countries in the 1960s, causing significant morbidity and mortality. This is supported by historical records and epidemiological data from that time period. Choices B, C, and D are incorrect because smallpox was not endemic in North America, England, or globally during the 1960s. Smallpox eradication efforts led to the global eradication of the disease in 1980, but in the 1960s, it was still prevalent in many developing countries.
What is the central component of the complement system?
- A. C1
- B. C2
- C. C3
- D. C5
Correct Answer: C
Rationale: The correct answer is C: C3. C3 is the central component of the complement system as it plays a crucial role in both the classical and alternative pathways by forming the C3 convertase enzyme. This enzyme initiates the cascade of reactions leading to opsonization, chemotaxis, and cell lysis. Choices A, B, and D are incorrect as C1 is the initiator of the classical pathway, C2 is involved in the formation of the C3 convertase, and C5 is necessary for the formation of the membrane attack complex.