Question

which of the following graphs is the most accurate representation of a humans immune response following the first exposure to an antigen?
a)
b)
c)
d)
graph a
graph b
graph d
graph c

Explanation:

When a human is first exposed to an antigen, there is a lag phase (no or very low antibody levels) as the immune system recognizes the antigen and activates B - cells. Then there is a rise in antibody titer as plasma cells produce antibodies. After the antigen is cleared (or the immune response subsides), the antibody titer decreases (but some memory cells remain). Graph A shows a lag phase (after the first exposure arrow), a rise in antibody titer, and then a decrease, which is characteristic of the primary immune response. Graph B shows a continuous rise which is not typical of the primary response. Graph C has an extremely long lag phase and then a very steep rise which is not in line with the normal kinetics of the primary immune response. Graph D has a relatively short - lived peak which is also not characteristic of the primary immune response.

Answer:

graph A