Multiple Choice Questions

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Chapter 6, Question 1.

1. The antigen–antibody reaction is used as the basis for many diagnostic tests investigating human diseases outside the immune system. A child with a bleeding disorder is suspected of having an inherited abnormality in von Willebrand's factor. The physician orders a quantitative monoclonal antibody-based assay and a qualitative functional assay. The quantitative assay results are within reference range (normal), whereas the qualitative assay shows a marked decrease in activity. Which of the following is one possible explanation for these results?

a. An error was made in the laboratory.

b. The antibody is detecting other cross-reactive molecules in the serum.

c. The cross-linking of the antibody falsely raises the level of antigen measured.

d. The factor has a mutation in its active site but not in the epitope to which the antibody is directed.