1. Immunoglobulin Structure & Function
Assigned Reading
Performance Ojectives
Key terms
Key Concepts
Content Outline
Short Answer Questions

2. Angels & Devils

3. Assigned Reading
Chapter: 5 pp
Janis Kuby’s Immunology 3rd Ed

4. Content Outline Basic Structure B Cell Receptor
Antigenic Determinants of Igs
Immunoglobulin Superfamily
Ig Classes
Monoclonal Antibodies (MABS)
Immunoglobulin Sequencing Studies
Immunoglobulin Fine Structure

5. Background

6. Tiselius

7. Electrophoresis

8. General Structure of Immunoglobulins
Electron microscopy
Crystallography
Hinge region
light & heavy chains
binding site
domains
fragments

9. IgG Crystal

10. X - Ray Crystallography
Crystallized Antigen or Antigen - Antibody Complex
Electron Density Map of the Molecule
Three Dimensional Images

11. Antibodies contain a flexible hinge region
EM evidence
Location
Chemical Structure
Advantages

12. Antibody Flexibility
EMs of same conc of antibody mixed with different conc of antigen
Ag-Ab complexes form different shapes
Ag is inflexible
AB MUST BE FLEXIBLE

13. Ag-Ab Complexes

14. Immunoglobulin flexible hinge

15. Hinge Prolines

16. Blocks or binds to antigens over a wide range of concentrations
Advantages of hinge
Rotation around central point
Bind antigens at various distances
Bind various ratios of antigens
Blocks or binds to antigens over a wide range of concentrations

17. Structure of IgG

18. IgG: Domains

19. IgG: Enzyme hydrolysis

20. Ag-Ab complexes after Pepsin

21. B Cell Receptor BEFORE IMMUNIZATION AFTER IMMUNIZATION
Ig genes are organized & Igs assembled
Anchored on membrane as specific receptors for immunogen
AFTER IMMUNIZATION
different expression of Ig genes
lose anchor>> secreted
different class of Ig secreted

22. Antigenic Determinants of Igs
Immunoglobulins are immunogenic
Inject human antibodies into a mouse
Mouse develops anti-Human antibodies
Use these antibodies to probe structure of immunoglobulins
Three classes of anti-antibodies
Isotypes
Allotypes
Idiotypes

23. Antibody Classes: Outline
5 classes of antibodies
Concentration of classes
Structure and function of
IgG
IgM
IgA
IgD
IgE

24. Immunoglobulin Classes
Immunoglobulin A IgA, mA
Immunoglobulin D IgD, mD
Immunoglobulin E IgE, mE
Immunoglobulin G IgG, mG
Immunoglobulin M IgM, mM

25. Immunoglobuin concentrations

26. Ig Superfamily

27. IgG: Physicochemical Properties
Molecular weight
Sedimentation constant 7S
Total 146,000
Heavy chain 51,000
Isotypes 4
Heavy chain domains 4
Carbohydrate (%) 2-3
half life (days) 21

28. Structure of IgG

29. IgG: Domains

30. IgG subclasses

31. IgG: Functions Bind antigen in tissue fluids
Promote destruction of antigen
activates complement
Promote phagocytosis
binds to Fc receptors on macrophages
Passive protection of fetus
binds to receptors on placenta
transferred to fetal circulation

32. Functions of IgG Domains
VH + VL Antigen binding
CH1 Complement binding c4b
CH2 complement binding C1q
CH3 Macrophage binding,Fc receptor
CH2 +CH3 neutrophil & K cell binding, bind to placental syncytiotrophoblast

33. Primary vs Secondary Response

34. IgM:Physicochemical Properties
Molecular weight
Sedimentation constant 19 S
Total 900,000
Heavy chain 65,000
Isotypes 1
Heavy chain domains 5
Carbohydrate (%) 12
half life (days) 5

35. IgM: Structure

36. IgM: Heavy chains

37. IgM: Functions Antigen receptor for B cell Short term protection
binds tightly to antigen
(high avidity)

38. IgA:Physicochemical Properties
Serum Secretory
Molecular weight
Sedimentation constant 7S S
Total , ,000
Heavy chain , ,56,000
Isotypes
Heavy chain domains
Carbohydrate (%)
Half life (days)

39. Structure of IgA

40. IgA dimers

41. EM of IgA

42. Secretion of IgA

43. IgA: Functions Protects body surfaces against invading microbes
Secretory IgA -
transported to epithelium
secreted in mucus, milk & tears
Blood IgA -
transported to liver
binds to hepatocytes
secreted into bile

44. J chain Small polypeptide chain
found in polymeric classes of antibodies
Acts as a clasp to join prototype subunits
produced by same cell that makes antibodies

45. J chain structure

46. J chain: Beta sheets

47. J Chain: Barrel

48. IgE: Physicochemical Properties
Molecular weight 188,000
Sedimentation constant 8S
Total 188,000
Heavy chain 72,500
Isotypes 1
Heavy chain domains 5
Carbohydrate (%) 12
half life (days) 2

49. Structure of IgE

50. Molecular model of IgE

51. IgE: Functions Mediates inflammatory response
Immunity to parasitic worms
Mediates many allergies (type I)

52. IgD Physicochemical Properties
Molecular weight
Sedimentation constant 7S
Total 184,000
Heavy chain 70,000
Isotypes 1
Heavy chain domains 4
Carbohydrate (%) 9-14
half life (days) 3

53. IgD Structure

54. IgD Hinge region

55. Substructure of IgD

56. Mouse IgD

57. Mouse IgD

58. IgD Function Activation of B cells by antigen
IgD : membrane antigen receptor
Indicator of Mature B cells
low levels of IgD & IgM in Bone marrow
high levels of IgD & IgM in peripheral lymphoid organs

59. DONE!!!

60. Performance Objectives

61. Key Terms
allotypes, allotypic determinants, Am determinants, Gm determinants,
Km determinants, Bence Jones proteins, Antibodies, immunoglobulin classes,
antibody subclasses, constant region (C), Fab fragment, Fab' fragment,
F(ab')2 fragment, Fc fragment, Framework residues (FR), Heavy chain,

62. hinge regions, chimeric antibodies, hybridoma, hypervariable regions (HVRs),
complematrarity determining regions(CDRs)
Hypoxantinine-Aminoopterin-Thymidine medium (HAT),idiotypes, idiotypic determinants,
immunoglobulin domains immunoglobulins, isotype, isotypic determinants,

63. joining chain (J), Light chain, monoclonal antibodies, multiple myeloma,
Secretory Iga, Segmental flexibility, variable regions (V)

64. Key Concepts
Distinguish between the overall structure and the fine structure of immunoglobulins
Describe the variable and constant regions of immunoglobulins light and heavy chains
Explain the structural organization of the variable regions of an immunoglobulins light and heavy chains

65. Differentiate between Hypervariable regions and complementarity determining regions
Contrast monoclonal antibody production vs polyclonal antibody production
Discuss the differences in the biological effector functions of the different classes of immunoglobulins

66. Diagram the procedure for monoclonal antibody production
Construct a table comparing the biological characteristics of the five classes of immunoglobulins
Construct a table comparing the biochemical and biophysical characteristics of the five classes of immunoglobulins

67. Short Answer Questions

68. The analysis of IgG molecules after hydrolysis by pepsin and papain led to similar yet different results. Explain.
What is the difference between and immunoglobulin and a myeloma protein?
Why were myeloma proteins and Bence Jones proteins critical to the early studies on antibody structure? What has largely replaced them?

69. Differentiate among, complementarity determining regions, hypervariable regions and framework regions.
Explain the statements: "Antibodies can be antigens" and "Antibodies can be used to characterize antibodies".
Discuss the terms immunoglobulin isotypes, immunoglobulin allotypes and immunoglobulin idiotypes and give examples of each.

70. Compare conventional antibody production with monocloanl antibody production and recombinant antibody production.
What are antibody domains?
Why can't light chains be used to classify antibodies?
The function of an immunoglobulin molecule is related to its structure. Explain.

71. Distinguish between idiotypes and anti-idiotypes.
Different cellular fusion products can potentially occur in a hybridoma fusion.
What are the potential products?
Why are they a problem?
How can you obtain the appropriate combination?
Distinguish between idiotypes and anti-idiotypes.