Which requires IL-2 and IL-4 for conversion to mature circulating cell?

Correct Answer: D

Rationale: The correct answer is D: T lymphocyte. T lymphocytes require IL-2 and IL-4 for conversion to mature circulating cells. IL-2 is crucial for T cell proliferation and differentiation, while IL-4 is essential for promoting T cell growth and differentiation into effector cells. Neutrophils (A) mature in the bone marrow, Eosinophils (B) primarily develop in response to IL-5, and B lymphocytes (C) mature in the bone marrow and require IL-7 for development.

Correct Answer: D

Rationale: The correct answer is D: Aplastic anemia. In a 50-year-old with infections, petechiae, and a dry marrow tap, the presentation is indicative of bone marrow failure, characteristic of aplastic anemia. This condition results in pancytopenia, leading to infections, bleeding (petechiae), and a dry tap on bone marrow aspiration. Iron deficiency anemia (A) typically presents with microcytic hypochromic red blood cells, megaloblastic anemia (B) with macrocytic red blood cells, and hemolytic anemia (C) with evidence of red blood cell destruction.

Correct Answer: C

Rationale: Step 1: Neutrophils, bands, metamyelocytes, myelocytes increased indicates a myeloproliferative disorder. Step 2: Basophils, eosinophils increased suggest a myeloid origin. Step 3: Platelets increased is common in chronic myelocytic leukemia (CML) due to myeloid proliferation. Summary: A is incorrect as it is associated with abnormal lymphoid cells. B is incorrect as it is a lymphoid disorder. D is incorrect as it is a lymphoid leukemia.

Correct Answer: C

Rationale: The correct answer is C because a hapten is a small chemical grouping that can bind to preformed antibodies but cannot induce an immune response on its own. Haptens require a carrier molecule to become immunogenic. Choice A (An epitope) is incorrect because an epitope is the specific part of an antigen recognized by an antibody. Choice B (A paratope) is incorrect as a paratope is the part of an antibody that binds to an antigen. Choice D (A carrier) is incorrect because a carrier is a molecule that can bind to a hapten to make it immunogenic.

Correct Answer: A

Rationale: Step 1: Basophils are a type of leukocyte, so they are included in the total leukocyte count. Step 2: Basophils make up less than 0.2% of total leukocytes in the blood. Step 3: Therefore, choice A is correct as basophils comprise a very small percentage of leukocytes. Summary: Choice B is incorrect as basophil granules stain with basic dyes like Toluidine blue. Choice C is incorrect as basophils have a shorter lifespan compared to several months. Choice D is incorrect as basophils play a key role in anaphylaxis through the release of histamine.