3 immunoglobulin

8/3/2019 3 Immunoglobulin

1/22

Immunoglobulin Structure and Function

, PhDMD


2/22

Immunogobulin, Ig

What isImmunoglobulin?

Immunoglobulins are the critical

ingredients of humoral acquiredimmune response.

The immunoglobulins are a group of

glycoproteins present in the serum and

tissue fluids of all mammals.


3/22

Immunoglobulins:Structure and

Function Definition: Glycoprotein molecules that are

produced by plasma cells in response to an

immunogen and which function as antibodies

Immune serum

Ag adsorbed serum

1 2

+ -

albumin

globulins

Mobility

Amount

ofprotein


4/22

General Functions of

Immunoglobulins

Effector functions

Fixation of complement

Binding to mast cells , macrophages, NK cell

(Usually require Ag binding)

Ag binding

Can result in protection

Valence


5/22

Basic Immunoglobulin Structure

Immunoglobulins - heterogeneous

Myeloma proteins - homogeneous

immunoglobulins


6/22

Two Forms ofImmunoglobulin

Membrane-boundreceptor Soluble antibody


7/22

Immunoglobulin Structure

Variable(V) &

Constant (C)

Regions

VL & CL

VH & CH

Hinge Region

CH1

VL

CL

VH

CH2

CH3

Hinge Region

Carbohydrate

Disulfide bond


8/22

Structural Regions


9/22

hypervariable

region

also called

Complementarity

Determining

Regions(CDRs),


10/22

Immunoglobulin Fragments:

Structure/Function Relationships

Fab

Ag binding

Valence = 1

Specificity

determined by VH

and VL

Papain

Fc

Fab

Fc ( crystallizable)

Effector functions


11/22

DomainsofImmunoglobulin


12/22

Function ofImmunoglobulins

Recognition of antigen

Activation of complement

Opsonization

Antibody-dependent cell-mediated

cytotoxicity,ADCC

Mediate hypersensitivity type I


13/22

Immunoglobulin Classes and

SubclassesImmunglobulin molecules are divided into

distinct classes and subclasses in terms of

the differences in amino acid sequence of

constant region of heavy chain,

i.e.,,,,andchains.


14/22

Immunoglobulin Classes ofMammals

IgG - Gamma () heavy chains

IgM - Mu () heavy chains

IgA - Alpha () heavy chains IgD - Delta () heavy chains

IgE - Epsilon () heavy chains


15/22

Five Classes ofImmunoglobulin


16/22

IgG has a family of subclass, IgG1, IgG2, IgG3,

IgG4(cattle has no)

IgA is divided into two subclasses, IgA1 and

IgA2(sheep).


17/22

Light Chain Types ofImmunoglobulin

Kappa ()

Lambda ()

All light chains have protein molecularweights of approximately 23,000 but can

be divided into two distinct types, namely

chain, chain, respectively


18/22


19/22

IgA

Structure

Serum - monomer

Secretions (sIgA)

Dimer (11S)

J chain

Secretory component

JChainSecretory Piece


20/22

IgA

Structure

Properties

2nd highest serumIg Major secretory Ig (Mucosal orLocal Immunity)

Tears, saliva, gastric and pulmonary secretions

Does not fix complement (unless aggregated)

Binds to Fc receptors on some cells


21/22

IgD

Structure

Properties

4th highest serumIg B cell surface Ig

Does not bind complement


22/22

IgE

Structure

Properties

Least common serumIg Binds to basophils and mast cells (Does not

require Ag binding)

Allergic reactions

Parasitic infections (Helminths) Binds to Fc receptor on eosinophils

Does not fix complement

3 immunoglobulin

Documents