Defination and general characteristics of antibody

Basic Principles of Antibody.

1. Presented by-
Dr. Abu Sadat Md. Sayem
M.Pharm, PhD. (University of Malaya)
Faculty of Pharmacy,
AIMST University
IMMUNOLOGY

2. FACULTY : PHARMACY
PROGRAMME : BACHELOR OF PHARMACY (HONS.)
COURSE CODE : PPTC 6420302
COURSE NAME : IMMUNOLOGY
STATUS : CORE
TOPIC : ANTIGEN AND ANTIBODY REACTIONS
DURATION : (3 HOURS) + TUTORIAL
Topic Learning Outcomes
Upon successful completion of this topic, students should be able to:
Describe the general characteristics of antigen and antibody reactions
(CL01).
Discuss the types of antigen antibody reactions (CL01).
Describe zone phenomenon (CL01).

3. TOPIC 2
Antigen and antibody reactions:
Describe the general characteristics of
antigen and antibody reactions
LECTURE 5

4. Antibodies are glycoproteins, produced by B-cell and circulated in the
blood stream and lymphatic system.
Antibodies are agents of humoral immunity that bind with antigens
(peptides molecules), viruses or bacteria.
These proteins are involved in immunological reaction and are therefore
called immuno-globulins (“Antibodies” and “Immunoglobulins” are
used interchangeably).

5. Basic Structure of Antibodies/ Immunologobulins
Immunoglobulin molecule is composed of four polypeptide chains with 2 identical
heavy chains and 2 identical light chains.
The polypeptide chains, heavy chains and light chains are linked to each other by
disulphide bond.
Further, the identical heavy chains are inter-bridged by a disulphide bond giving a Y
shaped structure.

6. Antibodies

7. Neutralization:
Antibody neutralization can prevent pathogens from entering and
infecting host cells
The neutralized antibody-coated pathogens, filtered by the spleen to
be eliminated in urine or feces.
Opsonization:
Antibodies, opsonize pathogens and mark them for destruction by
phagocytic cells.
Others functions:
Antibodies stimulate inflammation, while their presence in mucus and
on the skin prevents pathogen attack.

8. Types of Antibodies
Types Properties
Immunoglobulin G (IgG)
IgGs are the largest group of immunoglobulin class constituting
of about 80%.
Immunoglobulin M (IgM)
IgM constitutes about 5%-10% of the total immunoglobulin
class. Responsible for early stages of immunity.
Immunoglobulin A (IgA)
IgA are the second largest group of immunoglobulin class
constituting of about 10%-15%.
Immunoglobulin D (IgD)IgD constitutes about 0.2% of the total immunoglobulin class.
Immunoglobulin E (IgE)
IgE are the rarest group of immunoglobulin class constituting of
only 0.002%.

9. The type of heavy chain
 defines the overall class or isotype of an antibody.

There are five types of mammalian Ig heavy chains denoted by Greek letters:
α, δ, ε, γ and μ. These chains are found in IgA, IgD, IgE, IgG, and IgM
antibodies, respectively.
Types of Antibodies

10. IgG
IgG’s Fab arms are linked to the Fc arms by
an extended region of polypeptide chain
called the hinge.
IgG antibodies have been classified into four
subclasses; IgG1, IgG2, IgG3, and IgG4.
Exists in monomeric form.
Can cross the placenta from the mother to
the fetus.
Function:
Provide long-term protection against
bacteria, viruses, and bacterial toxins
most potent complement activators when
compared to all other antibodies.
Has most effective ability binding side &
enhances phagocytosis.
Fc region
Fab
region
Hinge
IgG
Types of Antibodies

11. IgM
Secreted in a pentameric form where
each are composed of two µ heavy chains
and two light chains
Has 10 binding domains in a single
molecule.
Molecular weight is 900kDa (largest Ab).
1
st
Ab to be produced in response to the
initial exposure to an antigen. (fetus at
20weeks)
Relatively short-lived & disappears earlier
than IgG.
Found in very low concentration in the
intracellular fluids
Function:
Effective against viruses
Has better agglutination affects.
Involved in activating the classical
pathway of complement system.
IgM
Types of Antibodies

12. IgA
Found in the mucous membrane in the form of
secretory antibodies
In small quantities in blood
High concentrations in tears, saliva, and sweat
Molecular size: 160 kDa with a four-chain
monomeric / dimeric / trimeric structure
Has polypeptide secretory component as an
additional component.
Has a J-chain linked to the chains via disulfide
bridges.
Secretory & J chain facilitates :
the transport of IgA across epithelial cells
protects the molecule from proteolytic
digestion by enzymes.
IgA
Types of Antibodies

13. IgA
2
nd
most abundant (2-4 mg/mL).
10-15% of the total serum concentration
first line of defense:
inhibiting bacterial and viral adhesion to
epithelial cells
neutralizing viral and bacterial toxins
intracellularly.
Secretion mostly in dimeric form
Function: Protects the body from the entry
and colonization of mucosal surfaces by
foreign particles.
Subclasses:
IgA1: monomeric form
IgA2: dimeric form
IgA
Types of Antibodies

14. IgD
Monomeric Ab
Presences on the surface of immature B
lymphocytes
glycoprotein with two identical δ heavy
chains and two identical light chains.
low concentration in serum (0.25 %).
Molecular weight: 185kDa
Half-life of 2 to 8 days
Function:
As antigen receptor on surface of B
cells.
regulates B cell function, if it
encounters an antigen.
Types of Antibodies

15. IgE
Found only in mammals
monomeric form with two ε heavy
chains and two light chains.
Function:
Associated with allergic reactions.
binds to antigens & triggers the
release of pharmacologically active
agents
Types of Antibodies

16. Application of Antibody
1.Used to treat immune deficiencies as a means of passive
immunity
2.Development of monoclonal antibodies has been used to treat
several diseases like multiple sclerosis & rheumatoid arthritis.
3.used in medical diagnostics as many biochemical assays for the
diagnosis of diseases
4.Different classes of immunoglobulins can be used to analyze the
antibody profile of patients.
5.Used to study the workings of different antigens and their
relationship with the host.

17. Polyclonal and monoclonal
antibodies

18. Monoclonal Antibodies (mAbs)
Monoclonal antibodies are identical immunoglobulins generated from a
single stimulated B cell clone. These antibodies are specific to only one
epitope of a single antigen.
Production of Monoclonal antibodies
•Production of monoclonal antibodies is done by introducing an antigen
of interest to a model organism (i.e., mouse).
•And the resulting B cells are then fused with myeloma cells. The
product of fusion of the two different cells is called hybridoma.
•The hybridoma cells are then cultured which continue to produce
antibodies against the specific antigen.
•Hybridoma cells have growth property of cancerous cell and antibody
producing property of normal B cell.
•Monoclonal antibodies are used as therapeutic agents in chemotherapy
and other immune diseases

19. Monoclonal Antibodies (mAbs)
Production of Monoclonal antibodies
The mouse is injected with antigens as is done for production of polyclonal antibody.
The animal is sacrificed and the plasma cells of such animal are extracted. These are
fused with the myeloma cells which form the hybridoma. These hybridoma cells in
culture produce the monoclonal antibodies.

20. Polyclonal Antibodies (pAbs)
Polyclonal antibodies are antibodies which are specific to more than
one epitope of an antigen. They are secreted by B cells in response to
specific antigens. Therefore, they can be defined as collection of
antibodies that bind to different epitopes of the specific antigen.
Production of Polyclonal Antibodies
1.An immunogen is injected into an animal
2.This will elicit a primary immune responses
3.Secondary & tertiary immunization is given to the animal to produce
higher titers of Abs against the particular antigen.
4.Blood is withdrawn from the animal, collect the serum and purified
the polyclonal Abs.

21. Differences between Polyclonal and Monoclonal antibodies

22. Thank You