Nokea
Why don't we have a successful HIV vaccine?
- A. The high mutation rate of HIV interferes with the generation of a protective memory response
- B. Because it is difficult to induce mucosal immunity that would block the sexual transmission of the virus
- C. Because HIV targets immune cells
- D. All of the above represent challenges for the creation of an effective HIV vaccine
Correct Answer: D
Rationale: The correct answer is D because all the statements in choices A, B, and C are valid reasons why we don't have a successful HIV vaccine.
A: HIV has a high mutation rate, making it challenging to generate a protective memory response.
B: Inducing mucosal immunity is difficult to block sexual transmission, a common route of HIV infection.
C: HIV targets immune cells, which hinders the immune system's ability to mount an effective response.
Therefore, all these factors combined pose significant challenges for creating an effective HIV vaccine.
You may also like to solve these questions
What is the main limitation of innate immunity compared to adaptive immunity?
- A. It cannot produce cytokines
- B. It lacks memory and specificity
- C. It does not include physical barriers
- D. It cannot activate complement
Correct Answer: B
Rationale: The main limitation of innate immunity compared to adaptive immunity is that innate immunity lacks memory and specificity. This means that innate immune responses do not improve upon repeated exposure to the same pathogen and cannot target specific antigens efficiently. Adaptive immunity, on the other hand, can remember previous encounters with pathogens and mount targeted responses. Choices A, C, and D are incorrect because innate immunity can produce cytokines, includes physical barriers like skin and mucous membranes, and can activate complement as part of its defense mechanisms.
Select incorrect mechanism for the development of autoimmune disorder.
- A. A second exposure to an allergen.
- B. Cross-reaction of antibodies formed against foreign antigens with self-antigens.
- C. Exposure of previously 'hidden' self-antigens to the adaptive immune system.
- D. Mutation followed by the appearance of membrane proteins not previously present.
Correct Answer: A
Rationale: The correct answer is A. A second exposure to an allergen does not lead to the development of autoimmune disorders. The key mechanisms involved in autoimmune disorders are self-tolerance breakdown and immune system attacking self-antigens.
Explanation:
1. B: Cross-reaction of antibodies formed against foreign antigens with self-antigens is a possible mechanism for autoimmune disorders.
2. C: Exposure of previously 'hidden' self-antigens to the adaptive immune system can trigger autoimmune responses.
3. D: Mutation followed by the appearance of membrane proteins not previously present can lead to autoimmune disorders, as the immune system may recognize these proteins as foreign.
Summary:
Choice A is incorrect because a second exposure to an allergen does not cause the immune system to target self-antigens, which is the hallmark of autoimmune disorders. Choices B, C, and D are more plausible mechanisms for the development of autoimmune disorders.
Which characteristic describes immunoglobulin E (select all that apply)?
- A. Assists in parasitic infections
- B. Responsible for allergic reactions
- C. Present on the lymphocyte surface
- D. Protects body surfaces and mucous membranes
Correct Answer: A
Rationale: IgE is involved in defense against parasites and is responsible for triggering allergic reactions by binding to mast cells and basophils.
Cells involved in allergic reactions include
- A. Mast cells
- B. Eosinophils
- C. Basophils
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D, "All of the above." Mast cells, eosinophils, and basophils are all involved in allergic reactions. Mast cells release histamine, leading to inflammation. Eosinophils are involved in allergic responses and parasitic infections. Basophils release histamine and other inflammatory mediators. Therefore, all three cell types play a crucial role in allergic reactions. Choices A, B, and C alone are incorrect because each cell type individually participates in allergic reactions.
The most abundant class of immunoglobulin in serum is
- A. IgE
- B. IgA
- C. IgD
- D. IgG
Correct Answer: D
Rationale: The correct answer is D: IgG. IgG is the most abundant class of immunoglobulin in serum, constituting about 75% of total immunoglobulins. IgG plays a crucial role in humoral immunity, providing long-term protection against pathogens. IgE (A) is involved in allergic responses, IgA (B) is mainly found in mucosal secretions, and IgD (C) functions as a cell surface receptor on B cells. IgG is the primary immunoglobulin responsible for secondary immune responses and provides the bulk of the adaptive immune response.