Nokea
Select the correct statement during an allergic reaction.
- A. An allergen binds with IgE antibodies.
- B. The mast cells are deactivated.
- C. The body is immunodeficient.
- D. Helper T cells release histamine.
Correct Answer: A
Rationale: Step-by-step rationale:
1. During an allergic reaction, allergens trigger the release of IgE antibodies.
2. The allergen binds with IgE antibodies, leading to the activation of mast cells.
3. Activated mast cells release histamine and other inflammatory mediators.
4. This cascade of events causes allergic symptoms.
Therefore, option A is correct as it accurately describes the initial binding of allergen with IgE antibodies. Option B is incorrect as mast cells are activated, not deactivated. Option C is incorrect as the body is hypersensitive, not immunodeficient. Option D is incorrect as it is mast cells, not Helper T cells, that release histamine.
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What is the primary role of phagocytosis in innate immunity?
- A. Killing cancer cells
- B. Engulfing and digesting pathogens
- C. Producing antibodies
- D. Activating complement proteins
Correct Answer: B
Rationale: The primary role of phagocytosis in innate immunity is to engulf and digest pathogens. Phagocytes such as macrophages and neutrophils recognize and engulf bacteria, viruses, and other harmful substances to prevent infections. They digest these pathogens using enzymes and destroy them. This process is crucial in the initial defense against infections. Option A is incorrect because phagocytosis primarily targets pathogens, not cancer cells. Option C is incorrect because producing antibodies is a function of adaptive immunity, not innate immunity. Option D is incorrect because activating complement proteins is a separate mechanism in the immune response.
Afferent lymphatic vessels do not
- A. Transport antigens from tissues to LN
- B. Enter LN at more than one site
- C. Transport antigens from blood to LN
- D. Connect tissues to secondary lymphoid organs
Correct Answer: C
Rationale: Rationale: Afferent lymphatic vessels transport lymph containing antigens from tissues to lymph nodes (LN). Option C is correct because afferent lymphatics do not transport antigens directly from the blood to LN. Other choices are incorrect because afferent lymphatics enter LN at multiple sites (B), transport antigens from tissues to LN (A), and connect tissues to secondary lymphoid organs (D).
Signal 2 for T cell activation is
- A. Necessary for re-activation of memory T cells
- B. Required to develop tolerance to self-antigens
- C. Mediated by CD3
- D. Essential for the activation of naïve T cells
Correct Answer: D
Rationale: The correct answer is D because Signal 2 is essential for the activation of naïve T cells. Signal 1 provides the antigen recognition, while Signal 2, typically provided by co-stimulatory molecules, is required for full T cell activation. A is incorrect because Signal 2 is not specifically for memory T cell re-activation. B is incorrect because Signal 2 is not related to self-tolerance, which is typically maintained by regulatory T cells. C is incorrect because CD3 is a component of the T cell receptor complex, not the primary mediator of Signal 2.
A clinical indicator of inflammation is:
- A. Decreased concentration of C3b
- B. Increased concentration of C-reactive protein
- C. Decreased concentration of MBL
- D. All of the above
Correct Answer: B
Rationale: The correct answer is B: Increased concentration of C-reactive protein. This is because C-reactive protein is a well-established clinical indicator of inflammation, produced by the liver in response to inflammation. Choice A is incorrect because a decreased concentration of C3b is not a typical indicator of inflammation. Choice C is incorrect because mannose-binding lectin (MBL) is an acute-phase reactant that increases in response to inflammation, so a decreased concentration of MBL would not be indicative of inflammation. Choice D is incorrect as it includes all options, but only B is a valid clinical indicator of inflammation.
Which antibody isotype is most abundant in circulation?
- A. IgA
- B. IgG
- C. IgE
- D. IgM
Correct Answer: B
Rationale: The correct answer is B: IgG. IgG is the most abundant antibody isotype in circulation, constituting about 75% of total antibodies. This is because IgG is produced during secondary immune responses and has a longer half-life compared to other isotypes, allowing it to accumulate in circulation. IgA is mainly found in mucosal surfaces, IgE is associated with allergic reactions, and IgM is the first antibody produced in a primary immune response. Therefore, IgG is the most abundant in circulation due to its longevity and role in secondary immune responses.