Abstract
Extract
When an immune serum is fractionated into its major components, for example by electrophoresis, the bulk of its antibody activity is seen to occur in the gamma globulins with some slight additional activity in the beta globulins. Proteins that have antibody activity are called immunoglobulins; these are divided into classes which differ in their structure and biology. Five such classes, designated IgG, IgM, IgA, IgD, and IgE, have been described in man. Immunoglobulins analogous to those of man probably occur in all mammals but in most species they remain to be specifically identified. Furthermore, the features of a given immunoglobulin class are broadly the same regardless of the species in which it occurs.