QS Study

Immunoglobin (Ig) are proteins of animal origin having antibody activity. Proteins of a similar structure having no Antibody (Ab) activity also called lg. It plays an essential role in the body’s immune system. They attach to foreign substances, such as bacteria, and assist in destroying them.

Such as in multiple myeloma malignant plasma cells produce myeloma protein which has no Ab activity though they an immunoglobin ( 2к or 2λ).


On the basis of amino acid sequence –

  • IgG Contains – γ Chain
  • IgA Contains – α Chain
  • IgM Contains – μ Chain
  • IgE Contains – ϵ Chain
  • IgD Contains – δ Chain

IgG antibodies are the most common and the most important. They circulate in the blood and other body fluids, defending against invading bacteria and viruses. IgA antibodies are present in tears, saliva, and mucus, as well as in secretions of the respiratory, reproductive, digestive, and urinary tracts. IgM is the main antibody produced in an initial attack by a specific bacterial or viral antigen, while IgG is usually produced in later infections caused by the same agent. IgE which is associated mainly with allergic reactions, it is found in the lungs, skin, and mucous membranes. IgD exists in small amounts in the blood, is the least understood antibody.


  • It passes from mother to foetus by placenta.
  • It has an antiviral activity.
  • It opsonizes the foreign body.
  • It helps in phagocytosis.