The major immunoglobulin family to which a particular immunoglobulin belongs can be determined by sequential analysis of the 110 amino acids beginning from the

Correct Answer: C

Rationale: The correct answer is C: Amino terminus of the heavy chain. This is because the amino acid sequence of immunoglobulins is determined by the heavy chain, making it crucial for identifying the immunoglobulin family. The heavy chain contains the variable (V), diversity (D), joining (J), and constant (C) regions essential for classifying immunoglobulins. Analyzing the amino terminus of the heavy chain allows for the identification of these regions, which are unique to each immunoglobulin class. The other choices are incorrect because the light chain does not contain the necessary regions for determining the immunoglobulin family, making the amino terminus of the heavy chain the key starting point for analysis.

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: A

Rationale: The correct answer is A: IgA. IgA is found in breast milk and plays a crucial role in providing immunity to the infant. It helps protect against infections in the digestive and respiratory tracts. IgM is primarily found in the bloodstream, IgD is mainly on the surface of B cells, and IgG is transferred from the mother to the fetus during pregnancy. IgA is the specific immunoglobulin class present in breast milk, making it the correct choice.

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.