In a study of the immune response, a volunteer was given two different antigens, X and Y. The level of antibody in the blood was recorded at regular intervals over 60 days. The graph indicates the time at which the volunteer was exposed to each antigen and shows antibody concentration against time for antigens X and Y. What is the explanation for the results shown on the graph?
- AA primary and secondary immune response against antigen X occurred, with the memory B-lymphocytes inhibiting the secondary immune response against antigen Y.
- BA primary immune response to antigen Y occurred and memory B-lymphocytes specific to antigen Y enhanced the secondary immune response to antigen X.
- CMemory B-lymphocytes specific to antigen X enabled a secondary immune response to occur; different B-lymphocytes were activated for a primary immune response for antigen Y.
- DPlasma cells remaining from the first exposure to antigen X undergo rapid clonal selection to produce high levels of antibody against antigen X and lower levels of antibody against antigen Y.