Immunoglobulins, also known as antibodies, are glycoprotein molecules produced by plasma cells (white blood cells). They act as a critical part of the immune response by specifically recognizing and binding to particular antigens, such as bacteria or viruses, and aiding in their destruction. The antibody immune response is highly complex and exceedingly specific. The various immunoglobulin classes and subclasses (isotypes) differ in their biological features, structure, target specificity and distribution. Hence, the assessment of the immunoglobulin isotype can provide useful insight into complex humoral immune response. Assessment and knowledge of immunoglobulin structure and classes is also important for selection and preparation of antibodies as tools for immunoassays and other detection applications.Immunoglobulins occur in two main forms: soluble antibodies and membrane-bound antibodies. (The latter contain a hydrophobic transmembrane region.) Alternative splicing regulates the production of secreted antibodies and surface bound B-cell receptors in B cells.Membrane-bound immunoglobulins are associated non-covalently with two accessory peptides, forming the B-cell antigen receptor complex. The first antigen receptors expressed by B cells are IgM and IgD. The receptor is a prototype of the antibody that the B cell is prepared to produce. The B cell receptor (BCR) can only bind antigens. It is the heterodimer of Ig alpha and Ig beta that enables the cell to transduce the signal and respond to the presence of antigens on the cell surface. The signal generated causes the growth and proliferation of the B cell and antibody production inside the plasma cell