immunoglobulins in easier way. make it as notes. direct way to read and practice. it is in very easy format and also in easy english.

1. Immunoglobulins
Presented by :- Tanmaya Toltia
& Sampad Kumar Khansama

2. What are Immunoglobulins ?
• Antibodies are specialized serum glycoproteins that are produced by lymphocytes
in response to an antigen & react specifically with that antigen.
• These are formed for self defense against antigen. Each have different amino acid
sequence & different antigen binding site. These antibodies are collectively called
IMMUNOGLOBULINS.
• In simpler word these are the glyco proteins. It contains 82-96% polypeptides & 4-
18% carbohydrates.
• These are most abundantly found protein components in the blood. They
constitute about 20% of the total protein component in the blood plasma.
• They identify the pathogen as a foreign substance by combining with several
antigens, creating a mass of clumped antigen-antibody complex.

3. Structure of Immunoglobulins
• These are Y shaped molecules & with 2 identical antigen binding sites. Because of
these 2 binding sites they are described as bivalent.
• The antigen binding sites are present on the tip of each arm of Y.
• They are composed of 4 polypeptide chains i.e. 2 identical light chain of polypeptide
(22000da) & 2 identical heavy chain of large polypeptide (55000da or more).
• Each light chain is bound to heavy chain by a disulfide bond & by non-covalent
interactions such as Salt bridge, Hydrogen bonds, Hydrophobic interaction to form a
heterodimer (H-L).
• Similar non-covalent interaction & disulphide linkage link the 2 identical
heterodimer to each other to form basic structure of antibody.

4. Structure of
immunoglobulins
 All Antibodies are
Immunoglobulins but all
Immunoglobulins are NOT
Antibodies.
 Antibodies are the antigen
binding proteins found on the
B-cell membrane and secreted
by the plasma cells of the
immune system.
 Antibodies are commonly
called as 'IMMUNOGLOBULINS.

5. Light Chains
• The light chain is composed of about 220aa residues. Around 100-110aa are
located at N-terminal (amino-terminal) & the aa sequence varies among
antibodies. This region of the L-chain is known as variable region.
• The remaining 110 aa located at C-terminal (carboxyl-terminal) of L-chain are
almost constant among antibodies. This region of L-chain is known as constant
region.
• 2 types of constant region sequence are found, i.e. lambda(λ)& kappa(k). In a
particular antibody either 2 lambda(λ) or 2 kappa(k) chains are present, but not
1 lambda(λ)& kappa(k).
• In human 60% light chain are kappa(k) & 40% are lambda(λ), but in case of
mice 95% of light chain are lambda(λ)& 5% are kappa(k).
• The N-terminal ends of the light & heavy chains together forms the antigen
binding site.

6. Heavy Chains
• In Heavy chain about 110aa are located at N-terminal, which shows great
variations among antibody. This region is known as variable regions.
• Remaining aa sequences of H-chain is constant but reveals 5 different types of
constant H-chain regions i.e. γ, ε, δ, μ, α. Those are known as isotypes.
• The length of constant region of h-chain is about 3-4 time longer i.e. (330 or 440
aa)depending on the class. 330 aa for α, δ & γ and 440 aa for μ & ε.
• The heavy chains of a given antibody molecules determines the class of that
antibody. For E.g. :- IgG(γ)
IgE(ε)
IgD(δ)
IgM(μ)
IgA(α)

7. Domain structure of Immunoglobulins
• The overall structure of immunoglobulin molecule is determined by primary,
secondary, tertiary & quaternary organization of aa molecules.
• The primary structure is sequence of amino acid that comprises variable &
constant region of heavy & light chains.
• The secondary structure is formed by folding of the polypeptide chain into series
of beta(β) pleated sheets.
• The secondary structure then folded into tertiary structure of compact globular
domains.
• These globular domains of adjacent heavy chains & light chain interacts in
quaternary structure, forming functional domains that enables binding sites for
antigens & the same time performs a no. of biological functions.

8. • 2 domains are found in L-chain
i.e. 1 in variable region (VL) &
other in constant region(CL) .
• In heavy chain, 1 domain is
found in variable region (VH) &
other in constant region(CH) .
• In IgA, IgD & IgG 3 domains are
found in constant region
{CH(1,2,3)}.
• In IgE & IgM 4 domains are
found in constant region of H-
chain {CH(1,2,3,4)}.

9. Various regions of immunoglobulins
1)Fab Region
• Antigen binding is accomplished by N-terminal region & effector function by
carboxyl terminal region of antibody.
• In an antibody molecule 2 Fab region are found & they binds antigen.
• Hypervariable region on L-chain (VL domain) & H-chain (VH domain) form antigen
binding site.
• The variability plot of VH & VL domains shows maximum variation in certain region
which is known as hyper variable region & this form antigen binding site.
• Antigen binding site is complementary to epitope of antigen, so it is also known as
complementary determining regions(CDRs).

10. 2) Fc Region
• Fc region of immunoglobulin allows for interaction of immune complex with
other phagocytic cells & complement.
• It takes part in various biological functions that are determined by aa sequences
of each domains of constant regions.
• Many different forms of Fc receptors exists.

11. 3) Hinge region
• The γ, δ, α heavy chain contains an extended peptide sequences between CH1 &
CH2 domain, that has no homology with other domain. This region is called Hinge
region.
• Hinge region is rich in proline residue & flexible. Therefore IgG, IgD & IgA are
flexible.
• The flexibility given by hinge region enable Fab region to assume various angle to
bind antigen.

12. Diagram showing
various region of
antibody

13. Classes of Immunoglobulin
• Immunoglobulins are classified into 5 different classes. i.e.

14. • IgG is the most abundant class of Ig in serum.
• It constitute about 80% of total serum Ig.
• IgG molecule consist of 2 γ (gamma) heavy
chains & 2 k (kappa)or 2 λ (lambda)light
chains.
• It has 4 sub classes (IgG 1,2,3,4) on the basis of
the decreasing serum concentration.
• The half life of IgG is about 23 days.
• Molecular weight is 150,000da.
FUNCTIONS
• It is the only Ig that can pass
through the placenta &
provide immunity to fetus up
to 6 month of age.
• IgG helps in bacterial
immobilization, neutralize
toxin and viruses.
• It produced in secondary
immune response.

15. • IgE accounts for 0.3% of total serum Ig.
• IgE is also known as reagenic antibody due to its
involvement in allergic reaction.
• Fc region of IgE binds on blood basophils &
tissue mast cell.
• The cross linkage of receptor binding IgE
molecules by antigen induces degranulation of
mast cell & basophil releasing histamine.
• Histamine is responsible for symptom of allergy.
• It mediate immediate hyper sensitivity reaction
& responsible for symptoms like asthma, hay
fever.
• Molecular weight is 200,000.
FUNCTIONS
• IgE provides immunity against
parasite by antibody dependent
self mediated cytotoxicity(ADCC).
• Level of IgE in blood of normal
individual is very low & its level
increases during parasitic
infnction & allergic reactions.
• IgE mediated degranulation is
necessary for antiparastic

16. • It is present in extremely low concentration.
• It constitute 0.2% of the total Ig in serum.
• IgD together with IgM is the major membrane
bound Ig expressed by mature B-cells.
• There are 2 sub classes of IgD. i.e. IgD1,IgD2.
• The molecular weight is 180,000.
• It is thought to function in the activation of B-
cells by Ag(Antigen).
FUNCTION
• It plays an important role in
maturation & proliferation of
B-cell.

17. • It is the 1st class of antibody made by a
developing B-cell.
• It accounts for 5-10% of total serum
immunoglobulin.
• IgM is secrete by plasma cell & it exist in
pentameric form, in which 5IgM monomers are
linked together by disulphide bond.
• It is the major antibody produced during
primary immune response.
• It is found on surface of mature B-cells
together with IgD, where it serve as an antigen
specific B-cell receptor.
FUNCTIONS
• IgM plays important accessory
role as secretory Ig due to J
chain.
• IgM has higher
valency(antigen binding site)
due to its pentameric form.
• It is more efficient then IgG in
complement activation.

18. • The molecular weight of IgA is 320,000da.
• It constitute 10-15% of total serum
immunoglobulin.
• It is the predominant immunoglobulin class
in external secretions such as breast milk,
saliva, tears & mucus of bronchial,
genitourinary & digestive tract.
• There are 2 sub classes of IgA. i.e. IgA1 &
IgA2.
• IgA exist as monomeric form primarily, but
also found in dimeric, trimeric & tetrameric
form also.
FUNCTIONS
• It is the major immunoglobulin found in the
colostrum of milk in nursing mother.
• It may provide the neonate with a major source
of protection against pathogen during the 1st
few week after birth.

19. Thank You