What happens when an antigen enters your body?

When an antigen enters the body, B-cells that recognize it, either from previous infection or being vaccinated, will produce antibodies. Once an antibody binds to an antigen, it signals other areas of the immune system to neutralize the harmful substances. This way, the body develops acquired immunity to specific diseases. B-cells attach to the antigen in a lock and key like manner. The B-cell will only make antibodies once its receptors test the antigen to see if they fit together. In contrast to B-cells, T lymphocytes neutralize antigens directly and help regulate the immune response. They also release cytokines, which control the entire immune response. It is important to note that antigens may also mutate and change shape. Thus, the immune system would be unable to recognize it and bind effectively as it did before.