A kidney biopsy specimen taken from a patient with acute glomerulonephritis and stained with fluorescein-conjugated anti-human IgG antibody would probably show

Correct Answer: C

Rationale: The correct answer is C: patchy, irregular fluorescence of the glomerular basement membrane. In acute glomerulonephritis, there is immune complex deposition in the glomeruli leading to inflammation. The immune complexes contain IgG antibodies, which will bind to the glomerular basement membrane. When stained with fluorescein-conjugated anti-human IgG antibody, the presence of IgG antibodies in the glomerular basement membrane will result in patchy, irregular fluorescence patterns. Choice A is incorrect as there should be fluorescence due to IgG deposition. Choice B is incorrect as the fluorescence pattern is not uniform. Choice D is incorrect as B cells are not typically involved in the pathology of acute glomerulonephritis.

Correct Answer: C

Rationale: The correct answer is C: a cell-mediated response. Poison ivy and poison oak reactions are primarily caused by contact with urushiol, an oil found in these plants. This oil triggers a cell-mediated immune response, involving T cells. T cells release cytokines that lead to inflammation and the characteristic rash. IgG and IgE responses are mainly involved in antibody-mediated immune responses, not in poison ivy reactions. Arthus reaction is a localized immune complex-mediated hypersensitivity reaction, not typically associated with poison ivy or poison oak.

Correct Answer: D

Rationale: The correct answer is D: indirect fluorescent-antibody test. This method is the best for demonstrating IgG on the glomerular basement membrane in kidney tissue. It involves applying a fluorescent-tagged anti-IgG antibody, which specifically binds to IgG on the tissue section, producing a visible fluorescent signal under a microscope. This technique allows for precise localization and visualization of IgG deposition. A: precipitin test and C: agglutination test are not suitable for detecting IgG specifically on tissue sections. B: complement fixation test is not commonly used for direct visualization of IgG in tissues. The indirect fluorescent-antibody test is the most sensitive and specific method for detecting IgG in tissue samples.

Correct Answer: D

Rationale: The correct answer is D because the statement is false. Antigens do not preselect V and J segments for gene recombination. Instead, the process is random. V, D, and J segments do combine to encode the antigen-binding site, making choice C true. Choice A is true because there are many V region segments available for gene recombination. Choice B is also true as there are several J segments and several D segments available for recombination. Therefore, the correct answer is D because it inaccurately describes the process of gene segment recombination.

Correct Answer: B

Rationale: The correct answer is B (sample B) because the double-diffusion test in agar against antibody to bovine albumin is specific for detecting the presence of bovine albumin. Since horse blood does not contain bovine albumin, sample B must contain horse blood. Sample A does not contain horse blood as it would not react with the antibody to bovine albumin. Both samples (C) cannot contain horse blood because the test is specific for bovine albumin. Neither sample (D) is incorrect because sample B does contain horse blood.