Question

question 49
2 points
a patients serum, mycobacterium, guinea pig complement, sheep red blood cells, and anti-sheep red blood cell antibodies are mixed in a test tube. what happens if the patient has antibodies to mycobacterium?
a hemolysis occurs.
b bacteria fluoresce.
c hemagglutination occurs.
d no hemolysis occurs.
e hemagglutination-inhibition occurs.

Explanation:

This is a complement - fixation test. If the patient has antibodies to Mycobacterium, the antibodies will bind to Mycobacterium, and then the complement will bind to this antigen - antibody complex. Since the complement is now used up in binding to the Mycobacterium - antibody complex, there will be no complement left to participate in the hemolytic reaction (which requires complement to lyse the sheep red blood cells that are coated with anti - sheep red blood cell antibodies). So, no hemolysis occurs. Option A is wrong because hemolysis needs complement, which is used up here. Option B is wrong as this is not a fluorescence - based test. Option C is wrong as hemagglutination is about agglutination of red blood cells, not relevant here. Option E is wrong as hemagglutination - inhibition is not the case here.

Answer:

D. No hemolysis occurs.