Nokea
The rearrangement of gene segments that occurs randomly in B cell receptor genes and T cell receptor genes:
- A. Occurs during clonal expansion of B cells and T cells
- B. Involves rapid genetic mutation after lymphocytes become activated
- C. Allows the mature lymphocyte population to recognize an enormous diversity of antigens
- D. Occurs in the DNA of all cells in the body
Correct Answer: C
Rationale: Step 1: Gene rearrangement in B cell and T cell receptor genes creates unique receptor proteins.
Step 2: This diversity allows mature lymphocytes to recognize a wide range of antigens.
Step 3: This process is crucial for adaptive immune response and antigen specificity.
Step 4: Choices A and B do not accurately describe gene rearrangement.
Step 5: Choice D is incorrect as gene rearrangement is specific to lymphocytes, not all cells in the body.
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A TH2 immune response will not induce
- A. Isotype switching to IgE
- B. Secret ion of IL-4
- C. Activation of macrophages
- D. Resistance to Leishmania infection
Correct Answer: E
Rationale: The correct answer is E because a TH2 immune response is associated with isotype switching to IgE and secretion of IL-4, which are essential for allergic responses. Activation of macrophages is not associated with a TH2 response. Resistance to Leishmania infection is mediated by a TH1 response, not TH2.
The activation of naïve T cells takes place in:
- A. Germinal centers
- B. Primary lymphoid tissues
- C. Secondary lymphoid tissues
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C: Secondary lymphoid tissues. Naïve T cells are activated in secondary lymphoid tissues such as lymph nodes and spleen. These tissues are where T cells encounter antigen-presenting cells, receive co-stimulatory signals, and undergo clonal expansion to differentiate into effector T cells. Germinal centers are primarily for B cell responses. Primary lymphoid tissues (bone marrow and thymus) are where T cells mature but not where activation occurs. Choice D is incorrect as naïve T cell activation does occur in secondary lymphoid tissues.
A protein-protein interaction domain present both in TLR-4 and MyD88 is:
- A. CARD
- B. TIR
- C. Leucine rich repeat (LRR)
- D. Immunoglobulin-like domain
Correct Answer: B
Rationale: The correct answer is B: TIR. This is because both TLR-4 and MyD88 contain a Toll/interleukin-1 receptor (TIR) domain, which mediates protein-protein interactions in the Toll-like receptor signaling pathway. The other options, such as A (CARD), C (LRR), and D (Immunoglobulin-like domain), are not present in both TLR-4 and MyD88 and do not play a significant role in their interaction in the signaling pathway. This makes B the most appropriate choice as it accurately identifies the common protein-protein interaction domain between TLR-4 and MyD88.
Which represents a correct grouping with respect to the target of an immune response, immune response strength, and resulting health status?
- A. Self-antigen, weak response, autoimmune disease
- B. Pathogen, strong response, recurrent infection
- C. Tumour antigen, weak response, cancer
- D. Transplanted organ, strong response, graft acceptance
Correct Answer: C
Rationale: Rationale:
1. Tumor antigens are non-self antigens that trigger a weak immune response due to immune tolerance.
2. Weak immune response against tumor antigens may lead to uncontrolled cell growth, resulting in cancer.
3. Strong immune responses are typically mounted against pathogens to clear infections.
4. Self-antigens should not trigger immune responses to prevent autoimmune diseases.
5. Transplanted organs can elicit strong immune responses leading to rejection, not acceptance.
Summary:
A - Incorrect: Self-antigens should not elicit immune responses to prevent autoimmune diseases.
B - Incorrect: Pathogens typically trigger strong immune responses to clear infections, not recurrent ones.
D - Incorrect: Transplanted organs often lead to strong immune responses and rejection, not acceptance.
Macrophages differentiate
- A. From blood neutrophils
- B. In tissues
- C. From the common lymphoid progenitor
- D. In the bone marrow
Correct Answer: B
Rationale: Macrophages differentiate in tissues because they originate from monocytes which leave the bloodstream and mature into macrophages in various tissues. This process is essential for their diverse functions in immune response and tissue maintenance. Choices A, C, and D are incorrect because macrophages do not differentiate from blood neutrophils, the common lymphoid progenitor, or in the bone marrow.