K4.2

: 95% in mouse

: 60% in human

IMMUNOGLOBULIN CLASSES

Opsonisation

agglutination

neutralisation

antibody-dependent cell-mediated cytotoxicity

complement activation

mast cell degranulation

protection of the neonate

Different immunoglobulin and their function

IgG

• Structure– Monomer (7S)

IgG1, IgG2 and IgG4

IgG3

IgG

• Structure• Properties

– Major serum Ig– Major Ig in extravascular spaces– Placental transfer – Fixes complement– Binds to Fc receptors

• Phagocytes - opsonization• K cells - ADCC

IgM

• Structure– Pentamer (19S)– Extra domain

(CH4)

– J chain CH4

J Chain

IgM• Structure• Properties

– 3rd highest serum Ig– First Ig made by

fetus and B cells– Fixes complement

Fixation of C1 by IgG and IgM Abs

C1r C1s

C1qC1r C1s

C1q

No activation Activation

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

IgA• Structure

– Serum - monomer– Secretions (sIgA)

• Dimer (11S)• J chain• Secretory

component

J Chain

Secretory Piece

IgA

• Structure• Properties

– 2nd highest serum Ig– Major secretory Ig– Does not fix complement unless

aggregated– Binds to Fc receptors on some cells

IgD

• Structure– Monomer– Tail piece

Tail Piece

IgD

• Structure• Properties

– 4th highest serum Ig– B cell surface Ig– Does not bind complement

IgE

• Structure– Monomer– Extra domain

(CH4)

CH4

IgE

• Structure• Properties

– Least common serum Ig– Allergic reactions– Parasitic infections– Does not fix complement

14B. IgG heavy chain variability

~200 variable region segments (V)~50 diversity regions (D)4 joining segments (J)5 constant regions (C)

15

V D J CDNA of precursor cell (not to scale)

random gene rearrangementB-cell DNA

mRNA

transcriptionand splicing

translation

C. Developmental gene rearrangements

19polyclonalmany antibodiesthat recognize many epitopes

monoclonalone antibodythat recognizesone epitope

various classes one class

making specificantibodies requirespurified antigen

specific antibodycan be made withimpure antigen

difficultreproducibility high reproducibility

A.

20B. Monoclonal antibody production

B-cells do not survive in culture

B-cell fused to myeloma cells produce hybridomas which survive in culture and produce antibody

Fusion is inefficient so a selectionfor hybridomas is used.

21immunized mouse

antibodyproducing

B-cells

mutant myeloma cellsfusion

hybridomas

cell mixture

22

well containing selective medium

test supernatant for antibody of interestdilute

retest for antibody of interest