The proteins in your blood plasma are composed of a mixture that is primarily albumin, and to a lesser extent, globulins. Globulin proteins are divided into four main classes: alpha-1 and alpha-2, beta, and gamma globulins. Gamma globulins are more commonly referred to as immune globulins, immunoglobulins, or antibodies. Antibodies are responsible for recognition and removal of harmful foreign agents from the body, including viruses and infectious bacteria.
Antibody Structure
Immunoglobulins are proteins that are produced by specialized white blood cells. There are five main classes of antibodies that are identified as immunoglobulin A (IgA), IgG, IgM, IgE, and IgD. All of the different classes of antibodies have nearly identical structure, with only small variations. Immunoglobulin proteins are Y-shaped and the components are divided by specific regions of that Y that include the heavy and light chain regions, the constant region and the variable region.
Heavy Chain
The immune globulin heavy chain component has five classifications that are defined by the Greek notations of alpha (A), gamma (G), mu (M), epsilon (E) and delta (D). Antibody class types are named according to their heavy chain type, hence the immunoglobulin alpha, or IgA subtype. Blood tests can measure the amount of certain antibody heavy chains and an imbalance may be indicative of certain types of blood cancers.
Light Chain
Immune globulin light chain components are approximately half the size of the heavy chains. There are two basic types of light chains, called the kappa and lambda. Kappa light chains are commonly seen in a two-to-one ratio in humans when compared to lambda chains. Blood tests that show an imbalance in this standard ratio is often used as a diagnostic for detecting certain white blood cell cancers.
Constant Region
The heavy and light chain components of the immune globulins contain a region that is called the constant region, which is virtually the same for all classes of antibodies. Due to the fact that this region is constant, it is always recognized by special components of the immune system that are responsible for destroying a foreign object like a virus or bacteria.
Variable Region
The variable region on both the heavy and light chains is the most important component of the immune globulin. The variable region is the antibody component that identifies a foreign object, like a virus or bacteria, and labels it as a threat to the body. The body's immune system will then always remember what that particular threat looks like, and will be able to easily destroy it. This process is what is necessary to establish immunity from a particular infectious agent. When new types of viruses or bacteria enter the body, the variable region will modify its structure to identify and label the new threat. Without the variable region, people would not have properly functioning immune systems.
