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Immunoglobulins: Structure and Function Aulanni’am Biochemistry Laboratory Faculty of Sciences_UB.

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Presentation on theme: "Immunoglobulins: Structure and Function Aulanni’am Biochemistry Laboratory Faculty of Sciences_UB."— Presentation transcript:

1 Immunoglobulins: Structure and Function Aulanni’am Biochemistry Laboratory Faculty of Sciences_UB

2 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1 22   + - albumin globulins Mobilit y Amount of protein

3 General Functions of Immunoglobulins Effector functions  Fixation of complement  Binding to various cells (Usually require Ag binding) Ag binding –Can result in protection

4 Basic Immunoglobulin Structure Immunoglobulins - heterogeneous Myeloma proteins - homogeneous immunoglobulins

5 Immunoglobulin Structure Heavy & Light Chains Disulfide bonds  Inter-chain  Intra-chain C H1 VLVL CLCL VHVH C H2 C H3 Hinge Region Carbohydrate Disulfide bond

6 Immunoglobulin Structure Variable & Constant Regions  V L & C L  V H & C H Hinge Region C H1 VLVL CLCL VHVH C H2 C H3 Hinge Region Carbohydrate Disulfide bond

7 Immunoglobulin Structure Domains  V L & C L  V H & C H1 - C H3 (or C H4 ) Oligosaccharid es C H1 VLVL CLCL VHVH C H2 C H3 Hinge Region Carbohydrate Disulfide bond

8 IgG molecule

9 Structure of the Variable Region Hypervariable (HVR) or complimentarity determining regions (CDR) HVR3 FR1 FR2 FR3 FR4 HVR1 HVR2 Variability Index Amino acid residue Framework regions

10 Immunoglobulin Fragments: Structure/Function Relationships Fab  Ag binding  Valence = 1  Specificty determined by V H and V L Papain Fc Fab Fc  Effector functions

11 Immunoglobulin Fragments: Structure/Function Relationships Ag Binding Complement Binding Site Placental Transfer Binding to Fc Receptors

12 Immunoglobulin Fragments: Structure/Function Relationships Fab  Ag binding Fc  Effector functions F(ab’) 2 Pepsin Fc Peptides F(ab’) 2

13 Human Immunoglobulin Classes IgG - Gamma (  ) heavy chains IgM - Mu (  ) heavy chains IgA - Alpha (  ) heavy chains IgD - Delta (  ) heavy chains IgE - Epsilon (  ) heavy chains

14 Human Immunoglobulin Subclasses IgG Subclasses  IgG1 - Gamma 1 (  1) heavy chains  IgG2 - Gamma 2 (  2) heavy chains  IgG3 - Gamma 3 (  3) heavy chains  IgG4 - Gamma 4 (  4) heavy chains IgA subclasses  IgA1 - Alpha 1 (  1) heavy chains  IgA2 - Alpha 2 (  2) heavy chains

15 Human Immunoglobulin Light Chain Types Kappa (  ) Lambda (  )

16 Human Immunoglobulin Light Chain Subtypes Lambda light chains  Lambda 1 (  1)  Lambda 2 (  2)  Lambda 3 (  3)  Lambda 4 (  4)

17 Immunoglobulins Nomenclature  IgM (kappa)  IgA1(lambda 2)  IgG Heterogeneity

18 IgG Structure  Monomer (7S) IgG1, IgG2 and IgG4IgG3

19 IgG Structure Properties  Major serum Ig  Major Ig in extravascular spaces  Placental transfer – Does not require Ag binding (  IgG2)  Fixes complement (  IgG4)  Binds to Fc receptors (  IgG2, IgG4) Phagocytes - opsonization K cells - ADCC

20 IgM Structure  Pentamer (19S)  Extra domain (C H4 )  J chain C4C4 J Chain

21 IgM Structure Properties  3rd highest serum Ig  First Ig made by fetus and B cells  Fixes complement

22 Fixation of C1 by IgG and IgM Abs C1r C1s C1q C1r C1s C1q No activationActivation

23 IgM Structure Properties  3rd highest serum Ig  First Ig made by fetus and B cells  Fixes complement Tail Piece  Agglutinating Ig  Binds to Fc receptors  B cell surface Ig

24 B Cell Antigen Receptor (BcR) Ig-  Ig- 

25 IgA Structure  Serum - monomer  Secretions (sIgA) Dimer (11S) J chain Secretory component J ChainSecretory Piece

26 IgA Structure Properties  2nd highest serum Ig  Major secretory Ig (Mucosal or Local Immunity) Tears, saliva, gastric and pulmonary secretions  Does not fix complement (unless aggregated)  Binds to Fc receptors on some cells

27 IgD Structure  Monomer  Tail piece Tail Piece

28 IgD Structure Properties  4th highest serum Ig  B cell surface Ig  Does not bind complement

29 IgE Structure  Monomer  Extra domain (C H4 ) C4C4

30 IgE Structure Properties  Least common serum Ig 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


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