antiboy or immunoglobulin
TRANSCRIPT
MUHAMMAD ASIF ZEBLECTURER HEMATOLOGY
IPMS
IMMUNOGLOBULIN
IMMUNOGLOBULINS
Immune serum
Ag-adsorbed serum
α1 α2 β γ
+ -albumin
globulins
Mobility
Am
ount
of p
rote
in
Igs are glycoproteins, produced in response to an immunogen by plasma cells
STRUCTURE OF ANTIBODIESSimply Y shape structureComposed 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 acidLight chain may be further divide into either kappa or lambda.Immunoglobulin may contain either kappa or lambda but not both
CONTI
Light and heavy chain are join to each other by disulfid bondThe 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.
IMMUNOGLOBULIN FRAGMENTS: STRUCTURE/FUNCTION
RELATIONSHIPS
Ag Binding
Complement Binding Site
Placental Transfer
Binding to Fc Receptors
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
IGG• Structure
• Monomer
IgG1, IgG2 and IgG4 IgG3
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
• 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 2Ig3 have highest ability to activate complement followed
by Ig1 and then Ig2 while Ig4 cant
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
IGM
•Properties• 3rd highest serum IgFirst 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
Fixation of C1 by IgG and IgM Abs
C1r C1s
C1q C1r C1s
C1q
No activation Activation
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
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
IGD
• Structure• Monomer
Tail Piece
IGD
• Structure• Properties
• 4th highest serum Ig• B cell surface Ig• Does not bind complement• Function is unknown but may important as lymphocytic
differentiation.
IGE
• Structure• Monomer• Extra domain (CH4)
Cε4
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
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