Question

One way to test if someone has immunity to a particular pathogen is to measure the antibody titer. What does it mean if someone has a positive antibody titer?

a) Previous exposure to the pathogen has caused T cells to attack the pathogen, leading to a more rapid response by T cells upon repeat exposure.

b) Previous exposure to the pathogen (or through a vaccination) has caused B cells to produce memory B cells. When re-exposed to the pathogen, they rapidly produce antibodies against the antigen (resulting in a positive antibody titer).

c) They must not have been exposed to the pathogen previously, meaning that they were able to rapidly produce antibodies.

d) They must not have been exposed to the pathogen previously, meaning that they were not able to rapidly produce antibodies.

Answer 1

Positive antibody titre means, he or she has detectable level of specific antibody present in his or her blood.

this is due to a previous exposure to the oathogen or may be vaccination, which has caused stimulate the B cell to produce memory B cells. When the person is reexposed to the pathogen again, the memory B cells rapidly responds and start producing antibodies against the antigen.
this is the basis of acquired active artificial immunity.

Option B is correct.