Antibody or Immunoglobulin

Content

• Introduction
• Structure
• Types

Introduction

• Antibody antigen binding glycoprotein present on B-cell membrane and secreted by plasma cells.
• The term antibody was first used by the scientists Paul Ehrlich.
• Membrane on antibodies refers antigenic specificity on B-cells.
• Secreted antibodies circulated, where they act as enhancer for stimulation of humoral mediated response, to neutralize antigens from the system.

The main categories of antibody action include:

1. 1. Neutralization
   2. Agglutination
   3. Precipitation
   4. Complement activation

• All antibodies share structural features bind to antigen and participate in several functions.

Structure of antibodies

• Antibody molecules have common structure of four polypeptide chains.i.e.2-light chains and 2 heavy chains respectively.
• Heavy chains consist of about 25000 molecular weight and light chain of 12000 molecular weight.

• Each Light chain is bound to heavy chain by non-covalent interaction.
• The light chain consists 220 amino acids while heavy chain consists of 440 amino acids.
• The Monomer has two kappa and two lambda
• Each antibody contains one or another type of light chains while consists of five types of heavy chains.
• Due to linkage of heavy chain and light chain antibody look like Y- shaped.

Types of antibodies

There are five classes of immunoglobulin molecules such as:

1. 1. IgG- Gamma
   2. IgA- Alpha
   3. IgE- Epsilon
   4. IgD- Delta
   5. IgM- Mu

• Heavy chains of antibodies had been named on Greek words each class of Ig plays important role in defense system.

IgG

• 50 to 80% antibodies contribute in the form of IgG in our serum.
• The maternal molecules can pass through placenta and provide passive immunity to fetus.
• These can also pass the cell walls of blood vessel.
• They are Monomer and molecular weight about 1,50,000 KD.
• They are responsible for neutralizing microbes and their toxins.
• They also enhance effectiveness of phagocytic cells to engulf and ingest them.

IgM

• They constitute about 5 to 10% in blood serum.
• It has pentamer structure.
• When expose to antigen, it is IgM that appears first.
• This specially cross linked particulate antigen and caused the aggregation due to numerous antigen binding site.
• Molecular weight about 900000 KD.
• It is very much effective as agglutination.

IgA

• Concentration of IgA in human blood remains about 15%.
• It consists J- chain with dimer.
• Molecular weight is about 3,20,000 KD.
• It is present in blood serum and surface of lymphocytes.
• It checks the attachment of pathogens to mucosal surfaces and protect the infants from infections.

IgD

• It accounts only 0.2% of serum.
• It is also Monomer and consist of 1,85,000 KD molecular weight.
• These are present on the upper surface of T- cells and it cannot pass across placenta.
• They assist initiation of immune responses and their population remains very high on the surface of the B – cells.

IgE

• The concentration of IgE is 0.02% of the total antibodies.
• They are larger than IgG.
• It responses quickly to the receptor of the mast cells and basophils.
• Mast cell and basophils are spread cells that take part in allergic reaction.
• Molecular weight is about 2 lakh KD.
• They raise in infections and responsible for allergic symptoms.

Reference and Sources

• 2% – https://www.scribd.com/presentation/364594715/Immuno-Log-i
• 1% – https://www.onlinebiologynotes.com/antibody-structure-classes-functions/
• 1% – https://quizlet.com/286582202/mbc-chapter-17-adaptive-immunity-specific-defenses-of-the-host-flash-cards/
• 1% – https://silo.pub/essential-immunology-for-surgeons.html
• 1% – https://quizlet.com/21778281/microbiology-exam-4-flash-cards/
• 1% – https://www.klimud.org/public/atlas/idrar/web/www.irvingcrowley.com/cls/glossary_all.html
• 1% – https://www.rbldiagnostics.com/testmenu/

Also Read:

• Immunoglobulin Classes: IgG, IgA, IgM, IgD and IgE
• Immunoglobulin: Introduction, Structure and function
• Antigen-Antibody Reactions: Uses, Stages and Features
• Polymerase Chain Reaction: Introduction, working and Components
• Molecular Detection of Microorganisms: Intro, Molecular methods, Applications