NIAID explains, "any substance capable of triggering an immune response is called an antigen. Each B cell is programmed to make one specific antibody. When a B cell encounters its triggering antigen (along with collaborating T cells and accessory cells), it gives rise to many large plasma cells. Every plasma cell is essentially a factory for producing antibodies."
According to NIAID, a given antibody matches an antigen much as a key matches a lock. The fit varies -- sometimes it's very precise, but other times it's little better than that of a skeleton key. To some degree, however, the antibody interlocks with the antigen and thereby marks it for destruction.
NIAID states, "Antibodies belong to a family of large molecules known as immunoglobulins. Immunoglobulins are proteins, made up of chains of polypeptides, strings of the basic units known as amino acids.
Each antibody has two identical heavy polypeptide chains and two identical light chains, shaped to form a Y. The sections that make up the tips of the Y's arms vary greatly from one antibody to another, creating a pocket uniquely shaped to enfold a specific antigen."
Related Explanations of Antibodies
NIH Pub 03-5423
- Antibodies: proteins (produced by white blood cells) which normally circulate in the blood to defend against foreign invaders such as bacteria, viruses, and toxins.
- Autoantibodies: instead of acting against foreign invaders as normal antibodies do, these attack the body's own cells.
- Antinuclear antibodies: a unique group of autoantibodies that have the ability to attack structures in the nucleus of cells.