Antigen - Antibody and their types

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Introduction:

         Our immune system generates a specific immune response and induces the specific antibody. Antibodies are soluble, Toxic, and present in bacteria, Viruses, RBCs, and other types of cells. Molecules or substances usually protein in nature and sometimes polysaccharides that generate a specific type of immune response and induce the formation of specific antibodies or specially sensitized T-Cells or both.

Antigen & Its type:

Two Main divisions of Antigen recognition:

• Foreign Antigen - Originate From the Outside of the body, Eg: Snake Venom, Serum, Vaccine, Micro-organisms, etc.

• Auto Antigen - Originate Within the Body, Eg: Autoimmune Disease, etc.

            Antigen recognizes Lymphocytes, to know about their nature. then provoke to make Antibodies. All Antigen doesn't Stimulate Lymphocyte and who does called as Immunogen. An antibody binds partially with an Antigen to those areas called an Epitope. An epitope is the Active region of an antigen. There could be multiple determinants in an Antigen. When Antibodies don't touch each other in an active site, Called as Non-Overlapping. 


 

Types of Antigen:

  • Based on Class or Origin:

    1. Exogenous Antigen: Start Circulating in blood fluid after entering the body
      • Trapped by APC( Antigen Processing Cell)

     i. Macrophase

     ii. Dendritic Cell 

      •  Enter through M.O.

     2. Endogenous Antigen: These are the Cells of the Body, Like -  Fragments of the body 

      •  Xenogenic
      • Autologous
      • Idiotypic/ Allogenic

     3. Auto-Antigen: Normal protein or Complex, DNA or RNA.

      • Which Causes Disease Ex.: Diabetes, Thyroid
      • Targeted to Immune System.

  •  Based on immune Response: 

    1. Complete Antigen / Immunogen: 
      • Protein in Nature or Polysaccharide 
      • Molecular mass is high.
      • Antigenic Properties, So it can generate immune responses.
    2. Incomplete Antigen/ Haptene:
      • Foreign Substance, Non-Protein in nature.
      • Can't generate the immune system Solely, So need a carrier to generate the immune response. this carrier should be protein in nature & Non-Antigenic for example Albumin, Globulin.
      • Binds with similar antibodies which are Specific. Pneumococcus and Streptococci are examples of incomplete antigens.

Antibody and its type:

           Antibodies are Y shaped, these are types of white cells That are also called immunoglobulin. B cell makes plasma after differentiation and Plasma cell starts making Antibodies. The molecular mass of an Antibody is 150 kilodaltons. An Antibody consists of 2 Light Chain and 2 Heavy Chain with Disulphide bonds. In the constant region of Antibody have a constant number of Aminoacids in every Antibody but in the Variable region, it differs from Antibody to Antibody. The variable region has the Antibody binding site.




Fab Region - Antigen Binding region

FC Region - Biological Activity Mediation Region.

Disulphide Region - Made up of Prolin Protein.

Light chain contains - 22,000 daltons polypeptides.

heavy chain contains - 50,000 daltons polypeptides.

Constant Region - Constant No. of Aminoacids

Variable Region - No. of AA varies in different Antibodies.

Each light and heavy chain contains 100-110 amino acids which is called Amino Terminal Region.

Types of Antibody:

  • Ig ( Heavy Chain) - IgG, IgM, IgA, IgE, IgD
  • Ig (Light Chain) - Lambda, Kappa.

There are 5 types of Immunoglobulin :

 

  1. IgG: 

  • It is Y shaped Antibody Present in abundant quantities 70-75%.
  • Detoxifies harmful substances. 
  • Through the leucocyte and macrophase recognize the Ag-Ab Complex.
  • IgG is transferred from mother to infant and stays there until the baby will grow. 
  • Subclasses are IgG1, IgG2, IgG3, IgG4.
  • Molecular Mass is 150 Kilodalton. 

     2. IgM:

  • It has Pentameric Shape and presents 10% in amount.
  • Circulates in Blood.
  • IgM activates first among all antibodies in microbial infection.
  • Makes pathway for signals.
  • It has less capacity than IgG but because of pentameric structure it is send first for attack.
  • Ingest the infected cell through the phagocytosis.

     3. IgA:

  • Present in abundant amount in serum, Nasal Mucus, Breast Milk, Intestinal Fluid.
  • Persent 10-15% in amount in blood.
  • It makes Dymer of immunoglobulin,
  • Protects from the worm in Gastrointestinal.
  • It creates first defense for Mucosal Surface.
  • Passes out with antigen through the secretion after binding with antigen.
    4. IgE:
  • Present in less amount about 0.001%.
  • It protects from parasitic attack.
  • Fights with pathogens.
  • It produces allergic reaction.

    5. IgD:

  • It presents 1% in amount.
  • Presents in some quantity in plasma membrane. 
  • Helps in production of antibody
  • Also called β-receptor because it receives antigen which are coming in β-cells.
  • It presents in plasma membrane of β-Cells.

 



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