Nokea
Which complement components are primarily involved in Type III hypersensitivity?
- A. C1 and C4
- B. C3a and C5a
- C. C5b and C6
- D. C2 and C7
Correct Answer: B
Rationale: The correct answer is B: C3a and C5a. In Type III hypersensitivity reactions, immune complexes form and deposit in tissues, leading to complement activation. C3a and C5a are anaphylatoxins released during complement activation, causing inflammation and tissue damage in Type III hypersensitivity.
Rationale:
A: C1 and C4 are primarily involved in Type I hypersensitivity reactions.
C: C5b and C6 are part of the membrane attack complex in the classical pathway of complement activation, not specific to Type III hypersensitivity.
D: C2 and C7 are involved in the classical pathway of complement activation but not directly implicated in Type III hypersensitivity reactions.
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The hypervariable regions
- A. Are also called Complementary Determining Regions
- B. Are localized in the constant region of an antibody molecule
- C. Are not found in the secreted form of antibodies
- D. Are found only in heavy chains
Correct Answer: A
Rationale: Step 1: Hypervariable regions are responsible for antigen binding specificity.
Step 2: Complementary Determining Regions (CDRs) are the specific locations within the hypervariable regions.
Step 3: As CDRs are part of the hypervariable regions, choice A is correct.
Summary: Choices B, C, and D are incorrect because hypervariable regions are not in the constant region, are present in secreted antibodies, and are found in both heavy and light chains.
Examples of disease-modifying drugs used to treat autoimmune disease include
- A. Corticosteroids
- B. Aspirin
- C. Anti-TNF-α
- D. C-cell depleting agents
Correct Answer: C
Rationale: Step-by-step rationale for why choice C (Anti-TNF-α) is correct:
1. Anti-TNF-α drugs target specific molecules involved in autoimmune responses.
2. By inhibiting TNF-α, these drugs reduce inflammation and slow disease progression.
3. This makes them disease-modifying, as they alter the course of the autoimmune disease.
Summary of why other choices are incorrect:
A: Corticosteroids are anti-inflammatory but not disease-modifying in autoimmune diseases.
B: Aspirin is primarily used for pain relief and reducing inflammation, not modifying the disease.
D: C-cell depleting agents are not commonly used for autoimmune diseases and do not target TNF-α.
Viral antigenic shift
- A. Is caused by multiple random mutations
- B. Is caused by a single mutation
- C. It affects only internal viral proteins not recognized by preexisting antibodies
- D. It refers to the appearance of new HA variants not recognized by preexisting antibodies
Correct Answer: D
Rationale: Step 1: Viral antigenic shift involves major changes in the surface proteins of the virus, particularly the hemagglutinin (HA) protein.
Step 2: These changes result in the emergence of new variants that are not recognized by preexisting antibodies.
Step 3: This process is distinct from antigenic drift, which involves minor changes due to random mutations.
Step 4: Choice D correctly states that viral antigenic shift refers to the appearance of new HA variants not recognized by preexisting antibodies.
Summary: Choice A is incorrect because viral antigenic shift is not caused by multiple random mutations. Choice B is incorrect as antigenic shift involves major changes, not a single mutation. Choice C is incorrect as it affects surface proteins like HA, not just internal proteins.
What role do Toll-like receptors (TLRs) play in the immune response?
- A. They identify self-antigens
- B. They mediate phagocytosis directly
- C. They recognize pathogen-associated molecular patterns
- D. They suppress cytokine secretion
Correct Answer: C
Rationale: The correct answer is C because Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) on pathogens, initiating the immune response. This recognition triggers the production of cytokines and chemokines, leading to inflammation and activation of immune cells. Choice A is incorrect because TLRs do not identify self-antigens but rather foreign antigens. Choice B is incorrect as TLRs do not directly mediate phagocytosis but rather initiate signaling pathways that lead to phagocytosis by immune cells. Choice D is incorrect because TLRs do not suppress cytokine secretion; rather, they stimulate cytokine production.
A segment of DNA that reads the same from forward and backward is called_____.
- A. Complementary DNA
- B. Palindromic DNA
- C. Copy DNA
- D. Transcribed DNA
Correct Answer: B
Rationale: The correct answer is B: Palindromic DNA. Palindromic DNA refers to a segment of DNA that reads the same from both directions. This property occurs when the nucleotide sequence on one strand of DNA is the reverse complement of the nucleotide sequence on the other strand. This symmetry allows the DNA sequence to be read the same forward and backward.
Incorrect choices:
A: Complementary DNA - Complementary DNA refers to a synthesized DNA strand that is complementary to a given DNA sequence.
C: Copy DNA - Copy DNA is not a commonly used term in molecular biology.
D: Transcribed DNA - Transcribed DNA refers to DNA that has been converted into RNA through the process of transcription, not DNA that reads the same forward and backward.