Immunoglobulins are heterodimeric proteins made up of two heavy (H) and two light (L) chains. They can functionally be divided into variable (V) domains that bind antigens and constant (C) domains that determine effector functions, such as complement activation or Fc receptor binding. The variable domains are produced by a complex series of events in gene rearrangement and can then be subjected to somatic hypermutation after antigen exposure. Each V domain can be divided into three regions of sequence variability, called CDRs, or complementarity determining regions, and four regions called framework regions, or FRs, of relatively constant sequence. The three CDRs of the heavy chain are combined with the three CDRs of the light chain to procedure the antigen binding site. Five major groups of heavy chain C domains exist. The isotypes of IgM, IgG, IgA, IgD, and IgE are defined by each class. To activate altered effector function while preserving antigen specificity, the constant domains of the heavy chain can be switched. The aim of this review is to review current development in our understanding of the structure, function and therapeutic effects of immunoglobulin, as well as the immunological implications of Ig for the management of autoimmune diseases and cancer. For that reason, a literature search on PubMed and Google Scholar was carried out using the specific keywords.