What is the most likely diagnosis for this patient? (17-year-old with fever, night sweats, painful lumps in neck/armpits when drinking)

Correct Answer: B

Rationale: The most likely diagnosis for the patient is B: Hodgkin lymphoma. The symptoms of fever, night sweats, and painful lumps in the neck/armpits are classic signs of Hodgkin lymphoma. The Reed-Sternberg cells seen in Hodgkin lymphoma are characteristic and differentiate it from non-Hodgkin lymphoma. Infectious mononucleosis typically presents with sore throat and fatigue, not painful lumps. Tuberculosis usually manifests with respiratory symptoms. Non-Hodgkin lymphoma may present similarly, but the presence of Reed-Sternberg cells points towards Hodgkin lymphoma.

Correct Answer: D

Rationale: The correct answer is D because a single B lymphocyte can produce antibodies of many different specificities due to the process of somatic hypermutation and class switching. This allows for the generation of a diverse repertoire of antibodies. Plasma cells, on the other hand, are derived from B cells and are typically monospecific, producing antibodies of a single specificity. This is important for maintaining a focused immune response. Explanation of other choices: A: Choice A is correct. Humans can indeed generate antibodies with approximately 10^8 different VH x VL combinations, contributing to the vast diversity of the immune response. B: Choice B is correct. A single B cell can switch from producing IgM antibodies to IgA antibodies through the process of class switching, enhancing the adaptability of the immune response. C: Choice C is correct. Hematopoietic stem cells possess the genetic potential to create over 10^4 immunoglobulin genes, which allows for the production of a wide array of antibodies

Correct Answer: B

Rationale: The correct answer is B because isotype switching involves the successive insertion of a single VH gene adjacent to different CH genes, leading to the production of antibodies of different classes. This process allows B cells to change the class of immunoglobulin they produce without altering the antigen specificity. Choice A is incorrect as it describes a mechanism different from isotype switching. Choice C is incorrect as it refers to the activation of genes on chromosome 6, which is not directly related to isotype switching. Choice D is incorrect as isotype switching specifically involves changing the heavy chain class of the immunoglobulin, not the light chain type.

Correct Answer: B

Rationale: The correct answer is B: cytotoxic hypersensitivity. Methyldopa can induce an autoimmune response causing hemolytic anemia by forming antibodies against erythrocytes. This type of reaction is characterized by the destruction of red blood cells by the immune system. The process involves antibody binding to the surface of red blood cells leading to their destruction by immune cells. A: Atopic hypersensitivity is commonly associated with allergies like asthma, hay fever, and eczema, not hemolytic anemia. C: Immune-complex hypersensitivity involves the formation of antigen-antibody complexes leading to inflammation but not direct destruction of red blood cells. D: Cell-mediated hypersensitivity involves T cell activation and is more associated with delayed responses like contact dermatitis, not acute hemolytic anemia.

Correct Answer: E

Rationale: I apologize, but it seems like there might be a mistake in the question as there is no option "E" provided. However, if we assume that the correct answer is missing and we need to select the affected immunoglobulin(s) due to the absence of J chains, the correct answer would be "C: IgA." J chains are essential for the polymerization and secretion of IgA antibodies. Without J chains, the production and secretion of IgA would be significantly impacted. IgG and IgM do not rely on J chains for their function, so options A, B, and D are incorrect in this context.