Immunoglobulins are proteins that are also called antibodies. The five different classes of immunoglobulins are formed in response to the presence of antigens. The specificity of an immunoglobulin for a particular antibody is exquisitely precise

The five classes of immunoglobulins are designated IgA, IgD, IgG, IgE, and IgM. These share a common structure. Two so-called heavy chains form a letter "Y" shape, with two light chains linked to each of the upper arms of the Y. The heavy chains are also known as alpha, delta, gamma, epsilon, or mu. The light chains are termed lambda or kappa.

The IgG class of immunoglobulin is the most common. IgG antibody is routinely produced in response to bacterial and viral infections and to the presence of toxins. IgG is found in many tissues and in the plasma that circulates throughout the body. IgM...