YOUR IMMUNE SYSTEM: B-CELL GUIDED MISSILES

While the T-cells in the lymph tissue are becoming sensitized to an antigen, certain B-cells begin to grow, change appearance and divide into generations of daughter cells called plasma cells. Plasma cells are like factories that manufacture antibodies. It takes only a few days for a single B-cell to grow into hundreds of plasma cells^each producing thousands and thousands of antibodies that “know” exactly which antigen they’re after. Imagine Zeus, the Greek king of gods, standing on Mount Olympus, hurling lightning bolts down to Earth, one after the other. Now picture hordes of plasma cells, throwing antibody after antibody at the invading antigens.

What are these antibodies? They’re called immunogolbulins, Ig for short. There are five categories of immunoglobulins: IgA, IgD, IgE, IgG and IgM. Shaped like a tiny “Y,” immunoglobulins have a constant portion (the bottom) and a variable portion (the top). It’s the variable portion that distinguishes one type of antibody from another.

Roughly 75 percent of the total immunoglobulins in a normal person are IgG. Along with IgMs, IgGs go after bacteria and viruses. IgE, of which there are few, are involved in allergic responses, while IgAs are assigned the task of protecting the musoca (the lining of the respiratory, gastrointestinal and urogenital tracts). When I want to know if a disease—hepatitis, for example—is recent or old, I look at the IgG and IgM counts. Elevated IgM indicates that the disorder is recent, while increased IgG points to an older problem.

Antibodies have several ways of dealing with antigens. Some strong antibodies can tackle the invader head on, ripping open the cell membrane and killing the antigen. Or the immunoglobulins can neutralize the enemy by covering up its toxic site. Another method is for multiple antibodies to bind themselves to antigens, clumping them together in a big bunch and rendering them harmless. (This is called agglutination.) There are other methods of attack, but antibodies are most effective when they work with other parts of your immune system, such as the complement system.