A group of glycoprotein molecules present in serum and body fluids of vertebrates are referred as immunoglobulins or Igs in short due to their involvement in immunological reactions and globular structure.
Immunoglobulins constitute about 20% of total plasma proteins and are responsible for humoral immunity. The plasma cells derived from activated B cells produce immunoglobulins to interact with foreign antigens. When an immunoglobulin binds with an antigen it is referred as antibody.
Even though all immunoglobulins are glycoproteins, all glycoproteins are not immunoglobulins. In a biological system glycoproteins perform various functions.
Cells use immunoglobulins (Ig) as multifunctional tools, to mediate interaction of antigens with effectors of cell mediated and humoral immunity.