The BEST method to demonstrate IgG on the glomerular basement membrane in a kidney tissue section is the

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: 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.

Correct Answer: B

Rationale: The correct answer is B: Only virus X-infected cells of HLA-B27 type will be killed. This is because cytotoxic T cells recognize antigens presented by HLA molecules. In this case, the cytotoxic T cells from an HLA-B27 person will specifically target virus X-infected cells that display antigens on HLA-B27 molecules. Choice A is incorrect because not all virus X-infected cells will be killed, only the ones with specific HLA molecules. Choice C is incorrect as not all HLA-B27 cells will be killed, only the virus-infected ones. Choice D is incorrect as the question specifically mentions virus-infected cells, not all HLA-B27 cells.

Correct Answer: D

Rationale: The correct answer is D. Naïve Th cells do not produce both gamma interferon and interleukin-4 simultaneously. They differentiate into Th-1 or Th-2 cells based on signals received. Th-1 cells produce gamma interferon and promote cell-mediated immunity, while Th-2 cells produce interleukin-4 and -5 and promote antibody-mediated immunity. Both Th-1 and Th-2 cells have CD3 and CD4 proteins, but this is not the least accurate statement among the choices.