Nokea
All of the following are true of antigen EXCEPT which one of the following?
- A. They contain paratopes
- B. They will react with antibodies.
- C. They contain antigenic determinants.
- D. They can elicit an immune response.
Correct Answer: A
Rationale: The correct answer is A. Paratopes are actually parts of antibodies that bind to antigens, not the antigens themselves. A is incorrect because antigens do not contain paratopes; rather, they contain epitopes or antigenic determinants that are recognized by antibodies. B, C, and D are true statements about antigens. B is true because antigens react with antibodies. C is true because antigens contain antigenic determinants that antibodies recognize. D is true because antigens can elicit an immune response by stimulating the production of antibodies. Therefore, the correct answer is A because antigens do not contain paratopes.
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Which of the following complement components is an opsonin?
- A. C3a
- B. C3b
- C. C4a
- D. C5a
Correct Answer: B
Rationale: The correct answer is B: C3b. C3b is an opsonin because it coats pathogens, making them more recognizable by phagocytic cells for ingestion and destruction. C3a, C4a, and C5a are anaphylatoxins that mediate inflammatory responses by activating immune cells, not opsonins.
In immune response mechanism clonal selection is a process in which:
- A. a special type of clone cell line is identified in a cell culture
- B. the proliferation and differentiation of lymphocytes occur in response to a specific antigen
- C. cloning of a specific gene is done by inserting the same into a bacteria by recombinant DNA technology
- D. selection of an appropriate cell type is done for the purpose of cloning
Correct Answer: B
Rationale: The correct answer is B because in immune response mechanism, clonal selection refers to the process where lymphocytes (T and B cells) proliferate and differentiate in response to a specific antigen. This process ensures that the immune system can effectively target and eliminate pathogens.
Option A is incorrect because clonal selection does not refer to identifying a specific type of clone cell line in cell culture.
Option C is incorrect because clonal selection does not involve cloning a specific gene by inserting it into bacteria using recombinant DNA technology.
Option D is incorrect because clonal selection is not about selecting an appropriate cell type for cloning purposes.
In summary, the correct answer, option B, best describes the process of clonal selection in the context of the immune response mechanism.
What triggers the release of mediators from mast cells during Type I hypersensitivity?
- A. Cross-linking of IgE molecules on the mast cell surface
- B. Activation of complement proteins
- C. Binding of IgG to antigen
- D. Phagocytosis of allergens
Correct Answer: A
Rationale: The correct answer is A. Cross-linking of IgE molecules on the mast cell surface triggers the release of mediators during Type I hypersensitivity. When allergens bind to IgE antibodies on mast cells, it leads to cross-linking of IgE molecules, causing the mast cell to release histamine and other inflammatory mediators. This process initiates the allergic response.
Explanation for incorrect choices:
B: Activation of complement proteins does not directly trigger mast cell degranulation in Type I hypersensitivity.
C: Binding of IgG to antigen is characteristic of Type II and Type III hypersensitivity reactions, not Type I.
D: Phagocytosis of allergens does not directly stimulate mast cells to release mediators in Type I hypersensitivity.
What is the consequence of granzyme entering a target cell?
- A. Neutralization of toxins
- B. Activation of apoptosis pathways
- C. Inhibition of cytokine secretion
- D. Promotion of antigen presentation
Correct Answer: B
Rationale: Granzyme entering a target cell activates apoptosis pathways by inducing cell death. Firstly, granzyme activates caspases leading to cell death. Secondly, it triggers DNA fragmentation and cell shrinkage. Lastly, it enhances membrane blebbing and apoptotic body formation. The other choices are incorrect because granzyme does not neutralize toxins, inhibit cytokine secretion, or promote antigen presentation within a target cell.
What is the key characteristic of adaptive immunity compared to innate immunity?
- A. It uses physical barriers like skin
- B. It has antigen-specific responses and memory
- C. It responds to all antigens non-specifically
- D. It is faster than innate immunity
Correct Answer: B
Rationale: The correct answer is B because adaptive immunity is characterized by antigen-specific responses and memory. This means that it can recognize and target specific antigens upon exposure and develop long-lasting immunological memory.
Choice A is incorrect because physical barriers like skin are part of innate immunity, not adaptive immunity. Choice C is incorrect as adaptive immunity responds to specific antigens, not all antigens non-specifically. Choice D is incorrect because adaptive immunity typically takes longer to respond compared to innate immunity due to the need for activation and clonal expansion of specific immune cells.