An important component of the immune system, antibodies are protein molecules made by B cells. The antibodies circulate in the bloodstream, attaching themselves to pathogens in order to identify invaders. Immune cells responsible for killing invading organisms can then recognize pathogens, and destroy them, in response to attached antibodies. While circulating antibodies certainly help the immune system to eradicate infection quickly, they don’t circulate all the time. Instead, they’re produced only as needed, in response to one of a number of signals of infection.
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First Time Antibody Production
The cause of initial antibody production is quite a complicated affair. If there’s pathogen in the bloodstream—a flu virus, for instance—the body doesn’t initially respond, explains Dr. Gary Thibodeau in his book, “Anatomy and Physiology.” Cells become infected by the virus, during which time the individual with the virus begins to experience symptoms of illness. The infected cells display distress signals, which are essentially composed of bits of the virus that is infecting them. Circulating B cells respond to these distress signals, and begin to produce antibody. The antibody attaches itself to viruses, marking them for eradication. Killer immune cells then destroy the viruses, eventually ridding the body of the infection.
Subsequent Antibody Production
The first time individual are exposed to a given virus or bacteria, they get ill. This is simply due to the time lapse between infection and production of antibody. Shortly after the initial infection has been eliminated, nearly all traces of antibody are gone from the bloodstream, but the memory of the viral infection remains in the form of what are called “memory” B cells, explains Dr. Lauralee Sherwood in her book, “Human Physiology.” The memory cells can start to produce antibody to a given virus immediately upon its appearance in the body during subsequent exposures, meaning that blood antibody levels increase much more rapidly than they did during the first exposure. Generally, the second time individuals come into contact with a given viral or bacterial infection, they don’t experience any symptoms—the antibody is produced so quickly as to lead to pathogen eradication before symptoms arise.
One very clever way to elicit production of antibody is to expose an individual to parts of a virus or bacterium without exposing them to the entire living pathogen. The immune system recognizes pieces of pathogens just as well as it recognizes the entire virus or bacterium, meaning that antibody—and memory B cell—production results from exposure to these pieces, but since the pieces aren’t whole pathogens, they can’t cause infection. This is one mechanism of vaccination. If an individual’s immune system has the opportunity to learn to recognize parts of a pathogen, it will be able to produce antibodies to that pathogen upon subsequent exposures, since it will have the memory B cells. The benefit of this method of producing antibody is that it doesn’t require initial infection, and through this route, many vaccinations confer immunity without causing illness.