Nokea
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.
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Which of the following is a primary lymphoid organ?
- A. Spleen
- B. Thymus
- C. Lymph node
- D. Mucosal immune system
Correct Answer: B
Rationale: The correct answer is B: Thymus. The thymus is considered a primary lymphoid organ because it is where T lymphocytes (T cells) mature and differentiate. T cells play a crucial role in the adaptive immune response. The thymus is responsible for educating T cells to recognize self versus non-self antigens.
Summary:
A: Spleen is a secondary lymphoid organ involved in filtering blood and producing antibodies, not where T cells mature.
C: Lymph node is also a secondary lymphoid organ where immune cells interact but not where T cells mature.
D: Mucosal immune system refers to the immune system in mucosal tissues, not a specific primary lymphoid organ.
Which rationale describes treatment of atopic allergies with immunotherapy?
- A. It decreases the levels of allergen-specific T helper cells.
- B. It decreases the level of IgE so that it does not react as readily with an allergen.
- C. It stimulates increased IgG to bind with allergen-reactive sites, preventing mast cell-bound IgE reactions.
- D. It gradually increases the amount of allergen in the body until it is no longer recognized as foreign and does not elicit an antibody reaction.
Correct Answer: C
Rationale: Immunotherapy stimulates the production of blocking IgG antibodies, which compete with IgE for allergen-binding sites, preventing mast cell activation.
Which of the following sentences is NOT true about type I hypersensitivity reactions?
- A. Symptoms manifest in allergic individuals only after a second encounter with an allergen
- B. Food allergies can result in systemic anaphylaxis
- C. TH2 lymphocytes are involved in their development
- D. They can be classified as genetic disorders because they are caused by a single gene defect
Correct Answer: D
Rationale: Step 1: Type I hypersensitivity reactions are immediate allergic reactions that occur upon initial exposure to an allergen, not just after a second encounter.
Step 2: Food allergies can lead to systemic anaphylaxis due to the rapid release of mediators like histamine.
Step 3: TH2 lymphocytes play a crucial role in the development of type I hypersensitivity reactions by promoting IgE production.
Step 4: Type I hypersensitivity reactions are not generally classified as genetic disorders since they result from an immune response to allergens, not a single gene defect.
Following class of restriction endonucleases is commercially available and used in recombinant DNA technology:
- A. Class 1
- B. Class 2
- C. Class 3
- D. Class 5
Correct Answer: B
Rationale: The correct answer is B: Class 2. Class 2 restriction endonucleases are commonly used in recombinant DNA technology due to their specificity for recognizing short DNA sequences and cleaving within or near these sequences. They are commercially available, easy to use, and have well-defined recognition sites, making them ideal for molecular cloning applications.
Choice A (Class 1) is incorrect because Class 1 enzymes require both ATP and S-adenosyl methionine for activity, making them less practical for routine laboratory use.
Choice C (Class 3) is incorrect because Class 3 enzymes cleave DNA at two sites, potentially leading to unwanted DNA fragmentation in recombinant DNA technology.
Choice D (Class 5) is incorrect because Class 5 restriction enzymes do not exist in the classification system of restriction endonucleases.
Which of the following best describes the immune system's role in tissue regeneration?
- A. Preventing pathogen invasion
- B. Promoting wound healing and cell debris elimination
- C. Increasing cytokine production
- D. Suppressing adaptive immunity
Correct Answer: B
Rationale: The correct answer is B because the immune system plays a crucial role in promoting wound healing and eliminating cell debris. When tissue is damaged, the immune response helps remove dead cells and debris, initiates the healing process, and supports tissue regeneration. This involves the recruitment of immune cells to the site of injury, releasing growth factors to stimulate cell proliferation, and resolving inflammation.
Choice A (Preventing pathogen invasion) is incorrect because while the immune system does play a role in preventing pathogen invasion, this is not directly related to tissue regeneration.
Choice C (Increasing cytokine production) is incorrect because although cytokines are involved in the immune response and can influence tissue repair, simply increasing cytokine production does not fully describe the immune system's role in tissue regeneration.
Choice D (Suppressing adaptive immunity) is incorrect because suppressing adaptive immunity would hinder rather than promote tissue regeneration, as adaptive immunity plays a role in immune memory and long-term protection against pathogens.