immunoglobulin are produce by the body against specific stimuli i.e antigen. antibody are of different types and these are classify according to there nature, temperature of reaction, structure and crossing of placenta. antibody are of Y shaped structure which is composed of different region. classification is based on the type of heavy chain, there are 5 major classes of antibodies, IgA, Igd, Igm, ige, most important of these are igm and igg, although each and every have there own significance.
3. STRUCTURE OF ANTIBODIES
Simply Y shape structure
Composed of 2 identical heavy polypeptide chains and 2 identical
light chain.
Heavy chain means have high molecular weight i.e 50,000-77,000d
and composed of 450 amino acid.
There are five chain classed of heavy chain i.e mu(u), gamma(r),
alpha(a), delta(&) and epsilon(e)
Light chain are smaller having molecular weight 25ooo and
composed of 212 amino acid
Light chain may be further divide into either kappa or lambda.
Immunoglobulin may contain either kappa or lambda but not both
4. CONTI
Light and heavy chain are join to each other by disulfid bond
The light and heavy chain is composed of constant and
variable region.
The first 110-120 amino acid of the light and heavy region
form variable sequence and thought to antigen binding site.
The constant region is further divide into C1H,C2H and C3h
each have their own function.
In the medal of antibody a region called hinge region which
gives feasibility to antibody.
6. HUMAN IMMUNOGLOBULIN CLASSES
Despite similarities, Abs are divided (size, charge,
solubility) into distinct classes and subclasses
• IgG - Gamma (γ) heavy chains
• IgM - Mu (µ) heavy chains
• IgA - Alpha (α) heavy chains
• IgD - Delta (δ) heavy chains
• IgE - Epsilon (ε) heavy chains
8. IGG
• Structure
• Properties
• Major serum Ig about 85% of imunoglobulin
• Monomeric structure
• Can cross placenta as have receptor on placenta
• Can Fixes complement (± IgG4)
• Opsonin antibodies and help in phagocytosis.
• Incomplete antibodies
• Best react at 37 c
9. • IgG Subclass
• IgG1 - Gamma 1 (γ1) heavy chains have 2 inter chain
disulfide bond
• IgG2 - Gamma 2 (γ2) heavy chains have 4
• IgG3 - Gamma 3 (γ3) heavy chains have 11
• IgG4 - Gamma 4 (γ4) heavy chains have 2
Ig3 have highest ability to activate complement followed by
Ig1 and then Ig2 while Ig4 cant
10. IGM
• Structure
• Pentamer , so it can
bind 10 antigen at a
time.
• Extra domain (CH4)
• Also contain J chain
which form disulfiod
bond with hinge region
• Diameter 300 Angstrom
• Length of monomer is
100 A
• 25-30 A width.
Cµ4
J Chain
11. IGM
•Properties
• 3rd highest serum Ig
First Ig made by fetus and B cells
• It Fixes complement
• Can not cross placenta
• Complete antibodies
• Usual temp 20c but best temperature is 4c
–Agglutinating antibody
12. Fixation of C1 by IgG and IgM Abs
C1r C1s
C1q
C1r C1s
C1q
No activation Activation
13. IGA
• Structure
• In Serum 90% occurs as monomer and 10% as
dimer.
• In Secretions (sIgA) 90% occurs as Dimer and
10% as monomer.
• SigA Have J chain in its structure
Also have Secretory component.
J ChainSecretory Piece
14. IGA
Properties
• It is 2nd highest serum Ig
• Major secretory Ig (Mucosal or Local Immunity)
• Tears, saliva, gastric and pulmonary secretions and server as first
lie of defense against microorganism invasion.
• Does not fix complement
• Cannt cross placenta
• Temp 37c
•IgA subtype
• IgA1 - Alpha 1 (α1) heavy chains
• IgA2 - Alpha 2 (α2) heavy chains
16. IGD
• Structure
• Properties
• 4th highest serum Ig
• B cell surface Ig
• Does not bind complement
• Function is unknown but may important as lymphocytic
differentiation.
18. IGE
• Structure
• Properties
• Least common serum Ig
• Binds to basophils and mast cells (Does not require Ag binding)
• Allergic reactions
• Binds to Fc receptor on eosinophils
• Does not fix complement
19. Abs: Molecules for immune effector system
a. Activate C’ – lysis & phagocytosis of microbes
b. Binds to Ag – enhance phagocytosis
c. Recognition of target
d. Stimulates degranulation of mast cells & release mediators
e. Cross placental barrier