1. Chapter 4 Immunoglobulin,Ig

2. discovery of Ig Antibody,Ab
antibodies is first discovered by Behring and Kitasato in 1890, antitoxin----(diphtheria exotoxin) capable of neutralizing the effects of toxin. r globulin,immunoglobulin
Immune serum---antiserum

3. Emial von Behring and Hidesaburo Kitasato were the first to show that antibody elicited in one animal can be transferred to another by injecting antibody with serum from the first
von Behring

4. antibody，Ab.
Ag→B cell→plasma cell→ antibody
Antibody---A protein that are produced by B cells that have differentiated to become plasma cells and that have the ability to combine with the antigen which stimulated its production.

5. Antibodies (Ab) are circulating proteins that specifically bind to antigen
Each antibody has a specificity different from the others antibodies
Each B cell makes ONE and only ONE type of antibody--clonal selection

6. gamma－globulin

7. immunoglobulin: globulins with antibody activity or its chemical structure is similar with Ab. Ig----structural and chemical Ab---biological and functional
All Abs are Igs, but not all Igs are Abs.
The terms Ig and antibody are used interchangeably.
secreted Ig，sIg——Humoral immunoresponse
membrane Ig，mIg——BCR

8. § 1 Structure of Immunoglobulin
Ig are glycoproteins.Each person is capable of producing at least 108 different antibody molecules.every immunoglobulin molecule is made up of two different types of polypepetides.
The larger,heavy(H2)chins are roughly twice as large as
The smaller,light(L2) chains.(H2L2)

10. 1、Basic structure of Ig
four-polypeptide chains unit， held together by a number of interchain disulfide bonds,form a Y-shaped construction，called Ig monomer，the basic unit.
amino-terminal---N terminal carboxy-terminal---C terminal

12. （1）heavy chain and light chain 1)、heavy chain，H
mW 50~75kD，each chain is composed 450~550 amino acids.heavy chains contain either four or five domains,each of which is amino acides long and contain a single intrachain disulfide bond.

13. Ig
IgM
IgG
IgA
IgD
IgE μ γ α ε δ Ab

14. 2)、light chain，L
mW 25kD，214aa.
 or  type， 1~  4 (subtype)

15. 1)、variable region(VH,VL)
（2）variable region and constant region
1)、variable region(VH,VL)
hypervariable region，HVR （complementarity-determining region，CDR）， HVR1（CDR1）、HVR2（CDR2）and HVR3（CDR3）-- antigen-binding site，
framework region，FR. VH and VL contain four FR

19. 2)、constant region(CH,CL)
CH: CH1、CH2、CH3、CH4：The chain C regions interact with other molecules and cell of the immune system and therefore mediate most of the biologic functions of antibodies.

21. 3)、hinge region
hinge region located between the CH1 and CH2 domains of the H chains.it is maded up predominantly of cysteine and proline residues.It provides an important flexibility of Ig

24. 4).domain

25. Function region： ①VH and VLis antigen-binding site.
②CH1 and CLgene mark
③CH2 can bind complement and Penetrating Placenta
④CH3 is binding cell FcR。

26. Ig β sheet--- β sandwich,
immunoglobulin folding
Conception of immunoglobulin superfamily,IgSF
It is membrane surface molecule that structure and gene similar to immunoglobulin and have recognized function is called immunoglobulin superfamily,IgSF

29. 2、other components of immunoglobulin
（1）joining chain,J chain
IgM sIgA generally include a single additional polypeptide is called the J chain.It is synthesized by all plasma cell that secrete polymeric Ig.Its function seems to be able to facilitate proper polymerization

30. （2）secretory piece，SP
It is a single glycopeptide with a peptide mW 7000,and is synthesized by mucosal epithelial cell,its function is resistant to proteolytic digestion

33. 3、 enzymatic digestion fragmentation of Ig
（1）papain
Ig molecules are cleaved by the enzymes papain allows separation of two fragment antigen binding，Fab2 and One fragment crystallizable，Fc1

35. （2）pepsin
Pepsin generates a single bivalent antigen-binding fragment, (Fab ’ ）2 and pFc’
Refine tetanus antitoxin with pepsin

36. § 2 heterogeneity( diversity) of immunoglobulin
classes and type in Ig

37. divided into subclasses basis
（1）class :Ig can be divided into classes on basis of difference the structure in CH .IgG、IgA、IgM、IgD and IgE。
（2）subclass:IgG and IgA can be
divided into subclasses basis
of difference the antigenic of CH and S-S: IgGl~IgG4, IgA—IgAl and IgA2

38. （4) subtype: leucine-- OZ（十）arginine-- OZ（一）in  190
（3） type : Ig can be divided into  and  basis of difference the structure in CL
（4) subtype: leucine-- OZ（十）arginine-- OZ（一）in  190

39. 3 endogenous—diversity of Ig epitope
exogenous ——diversity of antigen
endogenous—diversity of Ig epitope
serologic type of immunoglobulin ：
（1）Isotype:CH
（2）allotype:CH s-s
（3）idiotype，Id: Fab
anti-idiotype antibody，AId

42. § 3 Function of Immunoglobulin

43. 1、function of V region
Specifically binding with antigen

45. Virus-blocking Antibodies

46. 2、function of C region （1）activating complement
（2）binding to Fc receptor
1)、opsonization

49. 2)、antibody-dependent cell-mediated cytotoxicity，ADCC

51. 3)、 mediating type I hypersensitivity

54. （3） Penetrating Placenta and Mucous Membrane

57. § 4 Biological properties and function of every immunoglobulin

58. 1、IgG Monomer sedimentation coefficient---7s
molecular weight---150,000
begin to synthesize 3 months after birth, reach adult level in 3～5 y.
1) half-life long---23d
2) percent of total serum Ig---75% ～80%
subclass---IgG1, IgG2, IgG3, IgG4
3) main antibody when secondary immune response

59. 4) passage through the placenta 5) major anti-infection antibody
agglutination and formation of precipitate
4) passage through the placenta
5) major anti-infection antibody
Opsonization
antibody-dependent cell-mediated cytotoxicity
activation of complement
neutralization of toxin
immobilization of bacteria
neutralization of viruses
Binding with staphylococcus protein A，SPA，for diagnosis
Taking part in II、III type hypersensitivity

60. 2、IgM 1) Molecular mass of approximately 900KD,macroglobulin
2) In early primary production
3) BCR
4) Most efficient complement-fixing

62. 3、IgA
On B cell surfaces or in the blood , IgA exists as monomer comprising only one four-chain unit.
Secretion IgA,sIgA are dimers .it can be Local immune

63. 4、IgD
mIgD---BCR,auto-immune disease
The physiologic function of IgD is unknown

64. 5、IgE
1)Allergic response:mast cell and the basphil—carry 104 unique FcεR,
2)high –affinity :Fc ε R that is specific for IgE antibodies.
3) low concentration :IgE(10-7) in blood and tissue fluids.

65. § 5 preparation of artificial antibody
1.poly-clonal antibody，pAb
pAb is a complex mixture of antibodies recognizing multiple epitopes on the immunogen –Antiserum--antitoxin

66. 2. monoclonal antibody，mAb
(1).Conception:
mAb is a kind of antibody that is specific for one type of epitope and is produced by single B cell clone.It have high-specialang sensitivity
It is prepared by hybridoma technique and was described by Georges Kohler and Cesar Milstein in 1975
(2). preparation :
Immune B cell+myeloma→hybridoma →clonal →positive clones→expand →get antibody

68. (3)Applications
mAb have found numerous applications in diagnosis,as tools for clinical treatment,especially in cancer.for example, radioactively labeled mAb that recognize tumor.
Treatment –immunotoxin
Research application

72. 3.Genetic engineered antibody

73. Chimeric antibody
Reshaped antibody
Bispecific antibody
Phage antibody
Small molecule antibody(Fab; Fv ; single domain Ab;single chain Ab)