Nature of an antibody

NATURE

  • Antibody molecules are glycoproteins.
  • Tiselius and Kabat (1938) subjected immune serum to electrophoresis and separated its protein into four major fractions - serum albumin, alpha (α), beta (β) and gamma (γ) globulins.
  • Most immunoglobulins are found in the gamma fraction and some are in beta fraction.
  • Immunoglobulins are heterogeneous group of proteins and constitute about 20% of plasma proteins.
  • Based on sedimentation studies using ultracentrifuge, it was found that most antibody molecules sediment at 7S (Mol. Weight 150000Da) and some at 19S (Mol. Weight 900 000Da). ‘S’ stands for Svedberg unit = a sedimentation constant of 1 x 10 –13 seconds.
  • Protein molecules that bind specifically with antigen are called antibodies.
  • Proteins with antibody activity are called immunoglobulins.
  • The term immunoglobulin is a structural and functional concept; antibody is a biological and functional concept.
  • Immunoglobulins have been classified into five groups based on physicochemical and antigenic differences – IgG, IgM, IgA, IgD and IgE.
Last modified: Thursday, 26 August 2010, 5:16 AM