The first system of the complement fixation reaction consists of
Answer: D
Correct answer: an antigen, an antibody, complement
The first system is the reaction being tested: antigen, antibody and complement. If the antigen and antibody correspond, the complex fixes the complement and uses it up; if not, the complement is left free.
Please log in or register to report this question.
Patient serum contains
Answer: D
Correct answer: known antibody
In the usual serological test the patient’s serum is the source of antibody - and because the antigen used is known, an antibody detected by it is identified, that is, known. The unknown quantity is whether it is present and at what titre.
Please log in or register to report this question.
The material being tested contains
Answer: A
Correct answer: unknown antigen
The material being tested - a specimen from the patient or a culture - supplies the unknown antigen, and it is identified by reacting it against a diagnostic serum of known antibody.
Please log in or register to report this question.
Positive result of the complement fixation reaction is expressed in
Answer: A
Correct answer: complete inhibition of haemolysis
A positive result means the antigen and antibody did correspond, so the complement was fixed by their complex. None is left for the indicator system, the red cells stay intact, and they settle as a button - no haemolysis. It is an inversion that catches people out: no lysis means the test is positive.
Please log in or register to report this question.
Hemolytic serum for complement fixation reaction is obtained in the following manner
Answer: A
Correct answer: rabbits are immunized by suspension of sheep erythrocytes
Haemolytic serum is anti-sheep-red-cell antibody, and it is raised by injecting rabbits with sheep erythrocytes. The rabbit serum is then heated to destroy its own complement, so that the only complement in the final test is the one being measured.
Please log in or register to report this question.
Which of the following statements about the Fc fragment of an antibody is not true?
Answer: A
Correct answer: posses antigen combining activity
Antigen binding is the work of the Fab fragments, whose variable regions form the binding sites. The Fc fragment is the constant stem, and it carries the effector functions instead: complement fixation, placental transfer of IgG, and binding to cells - skin fixation by IgE, and opsonisation through Fc receptors on phagocytes.
Please log in or register to report this question.
Diagnostic serum contains
Answer: D
Correct answer: known antibody
A diagnostic serum is a reagent of known antibody, prepared by immunising an animal against a known organism. It is used to identify an unknown antigen - the organism isolated from the patient.
Please log in or register to report this question.
Negative result of the complement fixation reaction is expressed in
Answer: B
Correct answer: complete haemolysis
A negative result means antigen and antibody did not correspond, so no complex formed and the complement was not fixed. It is still free when the indicator system is added, and it lyses the sensitised red cells - complete haemolysis, giving a clear red solution.
Please log in or register to report this question.
The components for complement fixation reaction
Answer: A
Correct answer: an antigen, an antibody, complement, sheep erythrocytes, hemolytic serum
Five components in all, in two systems: antigen, antibody and complement in the first; sheep erythrocytes and haemolytic serum in the indicator system that reveals whether the complement survived.
Please log in or register to report this question.
A diagnosticum contains
Answer: C
Correct answer: known antigen
A diagnosticum is a standardised preparation of known antigen - killed bacteria, or antigen coated on carrier particles - used to detect the corresponding antibody in a patient’s serum. It is the mirror image of a diagnostic serum.
Please log in or register to report this question.
