Primary antibodies are parts of the body's immune system that attack foreign invaders in the body, such as bacteria, directly. Antibodies are designed to recognize and destroy or neutralize a specific virus, bacteria, or other unrecognized object found in a person's system. Antibodies are either primary, which means they bond directly to the targeted invader, or secondary, which means they instead bond to a primary antibody or the remnants of a destroyed invader. Both primary and secondary antibodies are used in scientific research to identify and monitor certain viruses or other microscopic agents.
When the body encounters an invader, known as an antigen, it creates an antibody to fight it. This antibody exists solely to seek out and destroy a specific type of antigen. Antibodies for a particular strain of the flu virus, for example, bond to that specific flu virus and destroy it before it has a chance to make the person sick.
Antibodies are Y-shaped and contain a region on the end of each branch of the Y known as a paratope. The paratope is shaped so it can bind with a particular antigen. Part of an antigen, known as the epitope, fits into the paratope and becomes trapped. Just as a puzzle piece fits into only one other puzzle piece, a primary antibody will accept only one specific type of epitope on an antigen. The antibody might block a specific strain of a virus, for example, but will not block all strains of the virus.
In contrast to the primary antibody is the secondary antibody, which does not bind directly to a foreign invader. Instead, it binds either to a primary antibody or a leftover fragment of the foreign invader. Secondary antibodies are used for scientific purposes to identify viruses and bacteria found in the body. The primary antibodies often are unlabeled, yet the secondary antibodies are. Once they bind to a primary antibody, the scientist can observe what types of primary antibodies and antigens are found in the sample.
The use of primary and secondary antibodies is important for understanding and researching diseases, such as Alzheimer's disease. Carefully controlled primary antibodies will bind to a very specific antigen, and scientists can use this knowledge to detect exactly what types of antigens are found in the body of a sick person. It also shows if an antibody is functioning improperly and attacking healthy elements instead of unwanted foreign elements and thus making the person even sicker.