Antibodies

Antibody is also known as  immunoglobulin. It is a protective protein synthesis  by our  immune system ,fighting with foreign substances, called an antigen. A wide range of substances are present  by the body as antigens, including disease-causing organisms and other insect related toxins when insects bite .Biochemically Antibodies are proteinaceous in nature. It is Also known as Immunoglobulin (Ig), Immunoglobulin consists of two words Immuno (Immunity) + Globulin (Protein) that is the protein which provides immunity to the body.

Structure of Antibodies

Antibodies are made up of four different protein (Polymer of Amino Acids) chains. Two Heavy Chain (H) and Two Light Chain (L), collectively called H2L2. These two chains are joined by disulphide chains, which form a Y shaped structure. There are two chains that exist in Antibodies – A Variable Chain and A Constant Chain. 

Variable Region – It is an Antigen Binding Site i.e have specific proteins which detects the specific Antigens. For this there is the Fragment Antigen Binding (FAB) part which binds with Antigens Specificity. 

Constant Region – This region binds with cell surfaces like Leucocytes (WBCs), NK cells (Natural Killer Cells), Macrophages. This region also has site Fragment Crystallisation (FC). This site helps to initiate the Immune Response.

Different Sites In Antibody –

Paratope – 

This is the site where Antigen binds, that’s why it is known as Antigen Binding Site.

Each Paratope has six CDRs ( Complementarity Determining Regions ) in which three have Heavy Chain and three have Light Chain.

Epitope – 

This is the site where Stimulates the immune response that’s why called Antigen Determinants. It binds only with specific antigen of B-Cells. 

Types of Antibodies –

There are five types of Antibodies-

1. Ig-G        2) Ig-M        3) Ig-A        4) Ig-E      5) Ig-D

1) Immunoglobulin (Ig) – G 

– It is amongst the most found antibodies in blood that is about 75%. 

– Most Studied Antibodies.

– Ig-G have also different subclasses – IgG1, IgG2, IgG3, IgG4, In order of abundance

IgG1>IgG2>IgG3>IgG4.

– IgG3 actively participates in the fight against HIV Virus.

– Ig-G is responsible for Humoral Immunity Response(Immunity provided by Fluid).

–  It is the Primary Biological Immune Defence System.

-It is the only antibody which crosses the Human Placenta during Pregnant, which provides Primary Immunity to Baby.

– This Antibody generally neutralises some pathogens like viruses.

2) Immunoglobulin (Ig) – M

– It is about 10% of total Antibodies

– This Antibody is used to diagnose the pathogen or Immunogen.

– It is more reactive than other antibodies, so binding with B-Cells shows the  active response fastly.

-This plays a role in the First Line Defence System.

3) Immunoglobulin (Ig) – A

-It is about 15% of total Antibodies.

-In Body is found in Human Saliva, Mucosa and Breast Milk.

-Ig-A is found in Colostrum (Yellowish Coloured Milk) formed during Breast Milk.

-It has two different Subclasses – IgA1, IgA2. maximum is IgA1 in the Mucosal tract (Mouth, Genitical Tract). 

4) Immunoglobulin (Ig) – E

-It is about 0.01% or less (minimum) of total antibodies.

-It is involved in Allergic reactions, also Basophils (A type of WBC) also secreted in the Blood.

5) Immunoglobulin (Ig) – D 

– It is about 0.5% or less of total Antibodies.

– It is generally active when Bacterias as pathogen enters in the body.

Applications of Antibodies – 

Diagnosis – Antibody plays an important role in diagnosing the diseases for Medical Purpose.

-Test ELISA ( Enzyme Linked Immunosorbent Assay ) is based on Antigen – Antibody interactions. It helps to detect infectious diseases.

-Antibodies are used to confirm the Pregnancy by using the Pregnancy Test. In this test Antibody binds with a specific chemical called HCG (Human Chorionic Gonadotropin) such that it gives a Positive test.

Biomedical Research – It involves several aspects like Chemical Therapy, ELISA, Western Blotting, etc.

In the Research area, Antibodies  help to understand the interactions of chemicals and their response to different Antigens.

– Development of different Drugs.

-Helps to understand Pathogen based studies.

Parental Therapy – In Blood (RBCs-Red Blood Cells) some factors are present which are responsible for Blood Grouping called Rh-factor.  If the Rh factor is present then the blood group is known as Rh+ve and if the Rh factor is not present in RBCs then called Rh-ve. 

-For a special condition called Erythroblastosis fetalis. This condition occurs during the second pregnancy of the mother, When Child is  Rh+ve while Mother is Rh-ve. During Delivery, when mother and child blood gets transfused which leads to the child to produce antibodies, this causes some Jaundice, RBCs disruptions in foetus blood.

Some Important Terminology – 

Serology – The Study of Antibody and Antigen.

Serum – Plasma minus Clotting Factors that is Blood contains RBCs, WBCs, Lymphocytes, Water, Proteins, etc.

Pathogen – These are small micro-organism when present in our body can interfere with our immunity, these may be in the form of Fungi, Bacteria, Virus, Protozoans, etc. Generally they cause Infectious Diseases.

Primary Response – Those responses generated by the body when it interacts with foreign substances for the first time. This response is of low Intensity.

Secondary Response – These responses generated by subsequent interaction with the same pathogens. This response is of High Intensity.

Conclusions:

Hence we concluded that Antibodies are proteinaceous substances present in blood which provide the active immunity from the pathogens. Antibodies are also known as Immunoglobulin (Ig). It is a protective protein synthesis  by our  immune system ,fighting with foreign substances, called an antigen. Antibodies have two heavy and two light chains, represented by H2L2.

There are five different types of Antibodies – Ig-G, Ig-A, Ig-M, Ig-D, Ig-E. Each has a specific role for providing immunity.It has two sites Paratope and Epitope for binding of pathogens and different cells which provide immunity respectively. 

There are different applications of Antibodies – Parental therapy, Biochemical Research, Diagnosis,etc