Antibodies

Summary

Antibodies are Y-shaped proteins produced by B-cells of the adaptive immune system. As a key player in our immune system’s humoral response, antibodies recognize and bind to antigens either as freely circulating proteins or as membrane-bound proteins. The antibody is made up of 2 light chains and 2 heavy chains, which come together to form variable regions on one end and a constant region on the other. The variable region is responsible for binding a wide variety of antigens, while the constant region works to alert other parts of our immune system to destroy whatever is bound by the antibody.

Key Points

• Antibodies (Immunoglobulins)
  • Main component of the humoral response of the adaptive immune system
  • Y-shaped proteins
  • Recognize and bind antigens
    • Binding to antigens attracts innate immune cells to phagocytose and destroy the pathogen
  • Produced by B cells
    • Each B cell makes a single type of antibody or immunoglobulin, which can recognize and bind to a specific antigen 
    • Can exist as membrane-bound cell receptors or independently in circulation 
  • Structure of an antibody
    • Two identical heavy chains and light chains
      • Connected by disulfide bonds
    • Both heavy and light chain involved in forming:
      • Constant region
        • Does not bind antigens
        • Signals to other cells (eg, phagocytes) and proteins to destroy antigen bound at other end
      • Variable region
        • Binds antigen
        • Unique amino acid structure of this region determines specificity of antibody