Another name of anti-body is immunoglobulins . Anti-body is the glycoprotein which is produce by Bcell and which are responsible to bind antigen with higher specifity and affinity. Anti-body is mainly distrusted in body fluid and also present surface of some cell.

1. RAYHAN
13-BATCH
Q. What is antibody ?
Another name of anti-body is immunoglobulins . Anti-body is the glycoprotein which is produce by B-
cell and which are responsible to bind antigen with higher specifity and affinity. Anti-body is mainly
distrusted in body fluid and also present surface of some cell.
Q. Write down the mechanism of antibody production ?
Anti-body produce by B-cell which are two forms. They are-
1 . Membrane bond form
2 . Secreted form
Membrane bond form – These act as antigen binding site. The interaction of antigen with antibodies
initializes B-cell response and thus regulate the recognization phase of humoral immunity. It act as B-cell
receptor.
Secreted form- These are produced by the activated B-cell which are involved effector mechanism of
humoral immunity eliminate the antigen. They are present in biological fluid
Effector mechanism –
1) Neutralization 2) Activation of complement 3) Activation of macrophage 4) Opsonization of
antigen.

2. Q . Describe the structure of anti-body ?
VH = Variable of heavy chain. VL= variable of light chain. CH= constant heavy chain. =
immunoglobulin domain. –s-s- = Disulphide bond.
Every antibody have a symmetrical core structure composed of
1 ) Two identical light chain
2 ) two identical heavy chain
Light chain is so called because their molecular weight is lighter than heavy chain. The molecular weight
of light chain is about 23-24 KD and consist of about 200 amino acids. On the other hand , the molecular
weight of heavy chain is 55-70 KD and consist of about 400 amino acids. One light chain is attached to
one heavy chain by a disulphide bond and two heavy chain are attached to each other by disulphide bond.
Every antibody has two antigen binding sites because they have two identical variable region.

3. Q . Describe the classification of antibody ?
According to the structural difference of constant region immunoglobulin are five types. Each types of
antibody are called isotype. They are- 1) Ig M 2) IgG 3) IgA 4) Ig D 5) IgE
1 . IgM
IgM represent about 8-10% of the total serum of immunoglobulin pool.
FUNCTION OF Ig M:-
1 ) IT is the first antibody that are immunologically commited to lymphocyte and gives the response to an
antigen.
2 ) they can be bind with complement system.
3 ) It has antigen receptor on the surface of B-cells.
4 ) it is the only antibody made to certain carbohydrate antigen.
2 . IgG
IgG is the major immunoglobulin in human serum according from 70-80% of total immunoglobulin pool.
FUNCTION OF IgG:-
1 ) It is the main antibody in the secondary response .
2 ) It opsonizes bacteria , making them easier to phagocytize.
3 ) It fixes complement , which enhance bacterial killing .
4 ) It neutralizes bacterial toxins and virus.
3 . IgA
IgA is present in two forms – 1) In the serum and 2) In various body secrstions.
IgA represent 15-20% human serum. Secretory IgA can be further IgA1 , IgA2.
FUNCTION OF IgA:-
1 ) It protect mucosal surface from pathogenic microbes.
2 ) It does not fix complement
3) Secretory IgA prevents attachment of bacteria.

4. 4) Ig D
Ig D represent less than 1% of the total immunoglobulin pool but is present in large amount of the
membrane of many b-cells.
FUNCTION OF IgD:-
1 ) Its true function is recognization and binding of antigen.
2 ) It acts as a regulator for synthesis of other immunoglobulin.
3 ) the antigen receptor for native B-lymphocyte.
5) IgE
IgE is represent in trace amount in the normal serum 0.05 mg/dl accunting for only 0.004% of total serum
immunoglobulin.
FUNCTION OF IgE:-
1 ) IT does not fixe complement .
2 ) It is responsible for the alargic reaction.
3 ) It is the main host defense helminth injection.
4 ) It mediates immediate hypersensitivity by causing release of mediator from mast cell and basophils
upon exposure to antigen ( allergen).
Q . Difference between antigen and antibody?
Antigen Antibody
1 Antigen is protein or non-protein substance
which produce immune response in our body
Anti-body is the glycoprotein which is produce by B-cell
and which are responsible to bind antigen with higher
specifity and affinity.
2 There are three basic kinds of antigen. There are five basic kinds of antibody
3 Antigen are made of either protein or
polysaccharide .
Antibody is made of organic structure unit.
4 Antigen can be cell. Antibody are not cell.
5 Antigen causes disease Antibody cure it