Answer:
The answer is antibodies.
Explanation:
Antigens are the molecules in the body that have the ability of causing an immune response to a disease whereas antibodies are protein molecules that are produced by the cells in the immune system for each specific disease. So if a doctor wanted to find out whether the person is immune to a disease or not by running a blood test, the focus should be on the presence of antibodies.
I hope this answer helps.
