FOOD ALLERGY AND MAST CELLS: FIGHTING INFECTIONS – THE VERSATILE ANTIBODY
Antibodies are special molecules produced by the body to fight off infections. They bind firmly to the bacteria or virus that causes the infection and, with luck, this stops the infection in its tracks. Antibodies can block infection in a variety of ways. With viruses, they may be able to prevent them from invading the body’s cells simply by binding to them. With bacteria, however, antibodies alone are ineffectual. They need help to defeat the bacteria and their job is to act as signals to other cells and molecules in the body which have the power to kill. The antibodies form a coat on the surface of the bacterial cells and this stimulates the immune system’s ‘assassination teams’ to go into action against the bacteria.
Antibodies are protein molecules, as are many of the important, hardworking components of the body (see p23). Proteins are infinitely variable molecules and this is what makes them so useful. In the case of the antibodies, their versatility is employed in making molecules that bind specifically to a particular target molecule, or antigen, and to no other. The measles virus, for example, is bound by antibodies that specifically recognize proteins in the outer coat of the virus – these being the measles antigens. They do not normally bind to anything else, apart from the measles virus.
The body produces a vast range of different antibodies – millions of them so that if it has to combat a new bacteria or virus it is certain to find an antibody ‘in stock’ that is just right for it. The antibodies are produced by special factory cells called B cells, and each B cell produces its own particular form of antibody. When faced with an invading microbe, the body selects a B cell with the right antibody to match that microbe, stimulates the cell to divide, and then instructs all the cells that are descended from it to produce their much-needed antibody. This continues until there is enough of the correct antibody to defeat the infection.
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