structure and types

1. Antibody

2. Antibody
Antibodies are produced in response to the invasion of foreign
molecules in the body.
An antibody is defined as ‘’an immunoglobulin capable of
specific combination with the antigen that caused its
production in a susceptible animals.’
Human immunoglobulins are group of structurally and
functionally similar glycoprotein that confer humoral
immunity.

3. Structure
 Antibodies exist as one or more copies of a Y-
shaped unit, composed of four poly peptide chains.
 Each Y contains two identical copies of light chain,
and two heavy chain , named as such by their
relative molecular weights.
 This Y-shaped unit is composed of the two variable,
antigen specific F (FC) arms, which are critical for
actual antigen binding and the constant “FC” tail
binds immune cell FC receptors.

4. Subclasses
 Antibodies can be divided into five classes : IgG, IgM,
IgA, IgD, and IgE based on the number of Y units and the
types of heavy chain.
 Heavy chains of IgG, IgM, IgD, IgG and IgE are known as
ɣ, µ, ,α, €, respectively.
 The light chains of any antibody can be classified as
either a kappa (ƙ) or lambda (ƛ) type.

5. 1.IgA:
 In the blood IgA are present in low level in numeric
from.
 They are most active at a mucosal surface where
they are present in dimeric from.
 IgA is produced in mucosal lining that are other
types of antibody combined.
 It major function is to act as a neutralizing
antibody.

6.  High levels of IgA present in saliva, tears, and breast
milk.
 IgA deficiencies are commonly seen in patients with
autoimmune disease and allergic disorders.
 IgA has a half-life of about 5 days.

7. 2.IgD:
 It is monomeric antibody with two epitope binding sites
and is found on the surface of most B lymphocytes.
 Its precise function is still disputed but is suggested to
acts as an antigen receptor required for B cell
activation.
 IgD also reported to bind to basophils and mast cells are
activated them to produce antimicrobial factors.

8.  It is also believed to play a role in eliminating B-
lymphocytes that produce self- reactive
autoantibodies.
 IgD has a half life of about 3 days.

9. 3.IgE:
 This group of antibodies is effective at mucosal surface,
blood and tissues.
 It is present as monomer consisting of two heavy chains
and two light chains .
 The E chain contains 4 Ig-like constant domains.
 Most IgE is tightly bound to its receptors on mast cells
and basophils via the FC region.

10.  It plays a crucial role in hypersensitivity reactions
and its production is strictly controlled by
cytokines.
 IgE has a half-life of about 2 days.

12. 4.IgG:
 This is the most abundant class of antibodies in the
blood, comprising up to 80% of the total serum
antibodies.
 It is present in monomeric from.
 Four subclasses of IgG have been described depending
on their abundance IgG1, IgG2, IgG3, IgG4.

13.  The subclass produced is dependent on the types of
cytokine present
 IgG has a half – life ranging from 7 to 23 days,
depending on its subclass.

14. 5.IgM:
 This class of immunoglobulin is first to be produced
in response to infection and is found either on
membranes of B cells or as a 5- subunit
macromolecule secrete by plasma cells.
 It is also the first immunoglobulin class to be
synthesized by the neotypes.
 This structure provides multiple binding sites.

16. Reference
 An Introduction to Antibodies and Their
Applications 3rd Edition by EMD Millipore.

17. Thank You