IMMUNOGLOBULINS - STRUCTURE,TYPES & FUNCTIONS - EASY NOTES

 Definition - 

• Specialized group of proteins having antibody activity are called as Immnuoglobulins.

• Functional term is immunoglobulin & Physical term is gamma globulin

• abbreviated as Ig.

STRUCTURE OF IMMUNOGLOBULINS

• Y-shaped tetramer 

• made of Two identical Heavy chains (H) &  Two identical Light chains (L) held together by interchain disulfide linkages and noncovalent interactions. 

• Each heavy chain has 450 amino acids

• Each light chain has 20 amino acids

• Each chain of Ig 
• has variable amino acid sequence at amino end called as the variable region (VL & VH)
• has constant amino acid sequence at carboxy end called as the constant region (CL & CH)

• The variable region ( both heavy & light chain )of the immunoglobulin is concerned with binding with the antigen

• Two types of light chains in all classes of Ig -- kappa (K) and lambda (λ)

CLASSES OF IMMUNOGLOBULINS & FUNCTIONS

• depending on the type of heavy chain Immunoglobulins are categorised under 5 classes -

1. IgG - major antibody of secondary immune response, present in all extracellular fluids
2. IgA- major antibody of body secretion, found in external secretions like colostrum, saliva, tears, gastric, nasal & bronchial fluids.
3. IgM -  major antibody of secondary immune response
4. IgD - found on the surface of B-lymphocytes 
5. IgE -  involved in allergic mediated (Type I) hypersensitivity.