Part 1
How do antibodies protect us?
When we are infected by a bacterium or virus, the operations of the human body are disrupted. One source of this are antigens, molecules produced by the virus or bacterium which induce a response by the immune system. One of the main reasons you feel so bad when you are sick is because your immune system has been activated by antigens and is now trying to remove them from your body.
Antibodies play an important role in the immune system's fight against antigens. Antibodies are Y-shaped proteins with receptors that have the capability of binding to an antigen. However, one antibody is not able to bind to every type of antigen, so different antibodies are produced which have different binding sites so that various types of antigens can be recognized. When the immune system comes across a new antigen it has not interacted with before, it responds by making lots of antibodies with different binding sites until it finds those capable of binding the new antigen. Antibodies do not bind to antigens but instead to an epitope, which is a portion of an antigen.
BINDING OF AN ANTIBODY TO AN EPITOPE
Image description: Left to right: antibody with green (dark and light) light chains and blue (dark and light) heavy chains. A cell with red circles and blue triangles symbolizing surface proteins. On the right, a second image of the antibody directly interacting with a round red circle on the cell's surface. Image created using Biorender.com.