This document provides information about immunoglobulins and their classification. It defines immunoglobulins as glycoproteins produced in response to antigens that can recognize and bind to antigens. The document discusses the occurrence, general chemistry including structure, functions such as antigen binding and complement fixation, digestion, and classification of immunoglobulins. It provides details on the subclasses of immunoglobulin G and the properties and functions of immunoglobulin D.