Which major advantage is specific to external fixation devices?

Correct Answer: C

Rationale: The correct answer is C: Greater freedom of movement. External fixation devices provide this advantage by allowing for adjustability and mobility of the affected limb. This is crucial for rehabilitation and preventing joint stiffness. Choice A (Faster healing time) is not specific to external fixation devices and can vary case by case. Choice B (Allowance for immediate weight bearing) may not always be recommended due to the complexity of the injury. Choice D (Pain reduction) is not a major advantage of external fixation devices, as they primarily focus on stabilizing fractures rather than directly reducing pain.

Correct Answer: C

Rationale: The correct answer is C: IL-10. IL-10 is known to polarize activated T cells towards a TH2 subset by suppressing TH1 cytokine production. IL-12 (A) promotes TH1 differentiation, IL-2 (B) supports T cell proliferation, and IL-5 (D) is involved in eosinophil activation and differentiation, not in polarizing T cells towards a TH2 subset.

Correct Answer: C

Rationale: The correct answer is C: Thymic medullary region. AIRE (Autoimmune Regulator) is expressed in the thymic medullary region. This region is crucial for central tolerance by deleting self-reactive T cells to prevent autoimmune reactions. AIRE regulates the expression of tissue-specific antigens in medullary thymic epithelial cells, leading to negative selection of autoreactive T cells. Choices A, B, and D are incorrect as AIRE is not primarily expressed in bone marrow, thymic cortical region, or LN cortex.

Correct Answer: B

Rationale: The correct answer is B: gp41. Gp41 is responsible for the fusion of the viral envelope with the cell plasma membrane by undergoing conformational changes that allow the viral and cellular membranes to merge. Gp120 attaches to the host cell receptor (CD4), facilitating the binding of the virus to the host cell. Gp160 is the precursor protein that is cleaved into gp120 and gp41 during viral maturation. CXCR4 is a cellular co-receptor used by some strains of HIV to enter host cells but is not directly involved in the fusion process.

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.