Which of the statements about the precipitin curve shown below is true?
|A||A solution in zone A would be expected to have unreacted precipitable antigen in the supernatant|
|B||A solution in zone C would be expected to have both antigen and antibody in excess|
|C||A solution in zone C would be expected to have an excess of antibody in the supernatant|
|D||In a monospecific system, a solution in zone B would contain only reacted antibody and antigen|
a. The ascending limb A of the precipitin curve presented in the question represents the zone of antibody excess; in this zone, the supernatant solution would contain unreacted antibody.
b. On the descending limb C, or the antigen-excess zone, the supernatant solution contains excess free antigen. In a monospecific system, B designates the region of maximum precipitation, and the supernatant solution is free to precipitate antibody and antigen.
c. In a complex multispecific system, excess antigen or antibody molecules may be present at the point of maximum precipitate formation because the optimal quantity of each antigen may be different.