Antibodies (or immunoglobulins) are proteins that are part of a large interconnected network of cells and molecules that are components of the mammalian immune system. Their primary function is the recognition of foreign substances (called pathogens) which is the first step in their eventual elimination from the body. Antibodies are synthesized by plasma cells in direct response to the presence of a pathogen. It is important to note that an antibody that is synthesized for (or in response to) a pathogen will have a specific affinity for it. The underlying biochemical process of complexing antibodies to pathogens is similar to that of enzyme-substrate interactions. Although antibodies are a single molecular species, they have the ability to recognize and bind to a wide variety of substances. There are 5 different classes of antibodies found in serum. They are Immunoglubulin A, M, D, E and G (gamma globulin). Although these classes of antibodies may differ in certain physical aspects and specific roles on immune response, they are all basically constructed the same way. For the rest of the tutorial we will be examining Immunoglobulin G as our model.
Enzyme Binding animation Catalytic Antibodies article Molecular Recognition article
Copyright 2006, John Wiley & Sons Publishers, Inc.
Sections 3.3, 6.4 
