Immunoglobulins

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Structure:-

  • Immunoglobulins are Glycoproteins made up of light(L) and heavy(H) polypeptide chains linked together by disulphide bonds.
  • Light chains have a molecular weight of 25,000 Da and Heavy chains have molecular weight of 50-70,000 Da.
  • They are Y-Shaped molecules made of 4 polypeptides:-
    • 2 Heavy Chains (H)-
    • 2 Light Chains (L)-
  • The Heavy chains consists of:-
    • 1 Variable Heavy(VH) region
    • 3 Constant Heavy(CH) regions- CH-1, CH-2, CH- 3
    • The region between CH-1 and CH-2 is called the Hinge Region which allows for better fit with the antigen surface.
  • The Heavy Chains may be of 5 types:-
    • Alpha
    • Gamma
    • Delta
    • Mu
    • Epsilon
  • The Light Chain consists of:-
    • 1 Variable Light(VL) region
    • 1 Constant Light(CL) region
  • Both the variable regions, VH and VL, form the ABS- Antigen Binding Site.
  • Enzyme digestion(Eg. Papain) splits the Ig molecule into two fragments:-
    • Fab: Antigen Binding Fragment
    • Fc: Complement Binding Fragment / Crystallizable Fragment

Functions:-

  • Protection against infectious agents
  • Enzymes to catalyse synthesis of ozone(O3) that has microbicidal activity