Nokea
What is true about OPV (Oral Polio Vaccine)?
- A. Induces mainly an IgG response
- B. Is currently the method of choice because considered safer than IPV (Inactivated Polio Vaccine)
- C. Induces mucosal immunity that blocks enteric infection and viral transmission
- D. All of the above is true about OPV
Correct Answer: C
Rationale: The correct answer is C because OPV induces mucosal immunity that blocks enteric infection and viral transmission. This is crucial in preventing the spread of poliovirus through the fecal-oral route. Choice A is incorrect because OPV primarily induces an IgA response in the mucosal surfaces, not IgG. Choice B is incorrect because while OPV is effective, it carries a risk of vaccine-derived poliovirus, making IPV the preferred choice in some situations. Therefore, Choice C is the most accurate as it highlights the unique ability of OPV to induce mucosal immunity, which is essential for preventing poliovirus transmission.
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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.
All of the following are true with respect to IgM antibodies EXCEPT which one
- A. they fix complement
- B. they occur on the surface of lymphocytes
- C. they predominate in the primary response to antigen
- D. mediate allergic reactions
Correct Answer: D
Rationale: The correct answer is D. IgM antibodies do not mediate allergic reactions. IgE antibodies are responsible for allergic reactions. IgM antibodies fix complement, occur on the surface of lymphocytes, and predominate in the primary response to antigens. IgM is the first antibody produced in response to an infection, playing a key role in the activation of the complement system. IgM antibodies are mainly found in the blood and lymphatic system, not on the surface of lymphocytes. IgE antibodies are the primary mediators of allergic reactions by triggering the release of histamine and other inflammatory molecules.
Which pathway of the complement system involves properdin, Factor B, and Factor D?
- A. Classical pathway
- B. Alternative pathway
- C. Lectin pathway
- D. Terminal pathway
Correct Answer: B
Rationale: The correct answer is B: Alternative pathway. This pathway involves properdin, Factor B, and Factor D. Properdin stabilizes the C3 convertase complex formed by Factor B and Factor D, leading to the amplification of the complement cascade. The other choices are incorrect because:
A: Classical pathway is initiated by antigen-antibody complexes binding to C1q.
C: Lectin pathway is activated by lectins binding to carbohydrates on pathogen surfaces.
D: Terminal pathway involves the formation of the membrane attack complex.
What is a characteristic feature of atopy?
- A. Tendency to produce IgE in response to allergens
- B. Excess production of IgA antibodies
- C. Suppressed immune response to allergens
- D. Delayed hypersensitivity reaction
Correct Answer: A
Rationale: Step-by-step rationale:
1. Atopy is a genetic predisposition to produce IgE antibodies in response to allergens.
2. IgE antibodies play a crucial role in allergic reactions.
3. Individuals with atopy have an exaggerated immune response to allergens.
4. Excess production of IgA antibodies (B) and suppressed immune response to allergens (C) are not characteristic features of atopy.
5. Delayed hypersensitivity reactions (D) involve a different immune mechanism compared to the immediate IgE-mediated response in atopy.
Which of the following is NOT commonly associated with granulomatous hypersensitivity?
- A. Crohn's disease
- B. Sarcoidosis
- C. Systemic lupus erythematosus (SLE)
- D. Tuberculosis
Correct Answer: C
Rationale: Granulomatous hypersensitivity is characterized by the formation of granulomas in response to persistent antigen exposure. Systemic lupus erythematosus (SLE) is an autoimmune disease involving immune complex deposition and inflammation, not granuloma formation. Crohn's disease, sarcoidosis, and tuberculosis are commonly associated with granulomatous hypersensitivity due to their chronic inflammatory nature and granuloma formation in affected tissues. SLE does not typically present with granulomas, making it the correct answer.