Which of the following is the most mature normoblast?

Correct Answer: A

Rationale: The correct answer is A: Orthochromic Normoblast. This is the most mature normoblast stage before becoming a mature red blood cell. The orthochromic normoblast has a small, condensed nucleus and minimal cytoplasmic basophilia. Basophilic normoblast (B) is an earlier stage with a larger nucleus and more basophilia. Pronormoblast (C) is the earliest stage with a large nucleus and intense basophilia. Polychromatic normoblast (D) is an intermediate stage with a slightly reduced nucleus and residual basophilia. Therefore, A is the most mature normoblast stage among the choices provided.

Correct Answer: C

Rationale: The correct answer is C: IL-3. IL-3 is a multilineage cytokine that stimulates the growth and differentiation of multiple blood cell lineages. It acts on various stem cells to promote the production of different types of blood cells. IL-1 is mainly involved in inflammation and immune response, not multilineage effects. IL-2 primarily regulates T cell growth and function. IL-4 promotes B cell growth and IgE production. Therefore, IL-3 is the correct answer as it is specifically known for its multilineage effects on blood cell development.

Correct Answer: B

Rationale: The correct answer is B: Ferrous. In the heme molecule, iron is present in the ferrous form (Fe2+). This form of iron allows for the binding of oxygen in hemoglobin. Ferro (A) is not a correct term for iron in heme. Ferric (C) refers to the Fe3+ form of iron, which is not found in heme. Apoferritin (D) is a protein that stores iron but is not directly involved in heme synthesis. Therefore, the correct form of iron in the heme molecule is ferrous (B).

Correct Answer: B

Rationale: The correct answer is B: Monoclonal protein in serum or urine. Multiple myeloma is characterized by the presence of abnormal plasma cells in the bone marrow, which produce monoclonal proteins. These proteins can be detected in the blood or urine through electrophoresis. Fever and infection (Choice A) are common symptoms but not specific to multiple myeloma. Elevated platelet count (Choice C) is not a characteristic feature of multiple myeloma. Normal bone marrow (Choice D) is not consistent with the disease, as multiple myeloma involves abnormal plasma cell proliferation in the bone marrow.

Correct Answer: B

Rationale: The correct answer is B because the principal difference between cytotoxic (type II) and immune complex (type III) hypersensitivity lies in the site where antigen-antibody complexes are formed. In type II hypersensitivity, the complexes form on the surface of target cells, leading to cell destruction. In contrast, in type III hypersensitivity, the complexes form in circulation or in tissues, leading to immune complex deposition and subsequent tissue damage. The other choices are incorrect because the class of antibody (A), participation of complement (C), and participation of T cells (D) can be common features in both type II and type III hypersensitivity reactions, but the crucial distinguishing factor is where the complexes are formed.