03抗体及其基因、B细胞发育(English version)_图文

ii .protecting sIgA from being proteolytic attack.
SC J chain
antibody-dependent cell-mediated cytotoxicity ()抗体依赖的细胞介导的细胞毒作用
Effector cell Ab
Target cell
DISTRIBUTION OF ANTIBODY:
Antibody molecules are found in serum, (account for approxinmately 20% of the total plasma pritein ),in extravascular Fluids（血管外液体）, in exocrine secretions(外分泌液）, and on the surface of some lymphocytes.
ADCC
Target cell
FcR
A form of nonspecific cytotoxic cell-mediated reaction in which an Effector kills an antibody-coated target cell,presumably by recognition of the Fc region of the cell-bound antibody through an Fc receptor present on the effector cell (e.g., NK cells, neutrophils,Macrophages).
IgG
2. Properties
a) IgG is the major Ig in serum - 75% of serum Ig is IgG
b) The longest half life(t ½ =23days)
c) IgG is the major Ig in extravascular spaces d) Placental transfer e) Fixation complement - Not all subclasses fix equally well;
papain:
-NH2 terminal side of interchain disulfide bonds in hinge region
Fab(Ag-binding Fragment)
(木瓜蛋白酶) papain
Fc(crystallizable Fragment): complement fixation
Figure 2 The basic structure of immunoglobulins
1.Heavy & light chains
1)Heavy chain: ① composed of about 500 a.a, oligosaccharide(+) ② Class :
heavy chain , , , , .
cell
IgA dimer
IgM
J CHAIN
Secretory piece
(2)presence: polymeric Igs such as IgM(pentamer),sIgA(dimer).
Joining chain
2)Secretory Piece(SC)
(1)chemical nature:
The relationship between AB & Ig: all antibodies are immunoglobulins, but it is
not certain that all immunoglobulins have antibody function.
Figure 1 Electrophoretic separation of serum proteins
immunoglobulin(Ig) IgA,IgG, IgM IgD, IgE
2) light chain: ① composed of about 214 a.a, oligosaccharide(-) ② type: ,
epitope
抗
Ab
原
CDR
Ag
Allotypic marker
5.Enzymatically generated Ab fragments
Macrophages, monocytes,.- Opsonization. NK cell, Macrophages---mediating ADCC
J链
3.Biological Activities
IgM
①pioneer antibody against infections
Opsonization
Polypeptide(70kD)
IgA dimer
(2)derivation:synthesized
by nonmotible epithelial cells near the mucos membrane where
secretions occurs.
(3)function: i.enabling IgA to be transported across mucosal tissues into secretions.
7-2 抗体分子的基本结构 Basic Structure of Ab Molecules
Gerald Edelman 1929 -Nobel Prize in 1972
Rodney Porter 1917-1985 Nobel Prize in 1972
HH
LL
Fab Fab Fc F a b
VL
two identical heavy chains , Fabheld by disulfide bonds(二硫
CL
键）。
2.Y-shape structure,
syemmetric.
3. –NH2 terminal, -COOH
Fc terminal 4.varible & constant regions.
5.domains: polypeptide
chains
folded by disulfide bonds
into glogular regions.
1.A basic unit composed of two identical light chains and two identical heavy chains ,held by disulfide bonds。 2.Y-shape structure, syemmetric. 3. N terminal, C terminal 4.varible & constant regions. 5.domains: polypeptide chainsfolded by disulfide bonds into glogular regions
the strongest anti-
(the strongest )
bacterial effect (500~1000×IgG)
Fixation complement Neutralizing virus
& toxin
Edelman
Porter
Varible region
Hinge region
Constant region
VH CH1
CH2 CH3 CH4
COO–
1.A four polypeptide chains
basic unit composed of two NH3+ identical light chains and
General structure of the four subclasses of human IgG,which differ in the number and arrangement of the interchain disulfide bonds linking the heavy chains. A notable feature of human IgG3 is its 11 interchain disulfide bonds.
Plasma cells
Ig
sIg
Ig
sIg
On binding their cognate antigens, surface Ig can initiate a cascade of molecular signaling events that may culminate in B-cell activation, clonal proliferation, and the generation of plasma cells. The immunoglobulins that are secreted function as ANTIBODY and bind to the specific antigens.
IgG4 does not fix complement f) Binding to cells –
• Macrophages, monocytes,.- Opsonization. • NK cell, Macrophages---mediating ADCC • SPA—Coagglutination Test
Membrane-boug Igb
2. Properties
a) the 3rd highest serum Ig
IgM
b) the first Ig made by fetus and B cells
c) intravascular Ig d) Fixation complement –classical pathway e)the largest size of molecule f)agglutinating microbes e) Binding to cells –