1. Antibodies

2. Introduction Definition:
Immunoglobulins represent animal proteins, which
possess antibody activity and other proteins with
related chemical structure and antigenic specificity.
(according WHO)

3. Antibodies
Structure

4. Immunoglobulin structure
Heavy chain
IgM, IgG1-4, IgA1-2, IgD, IgE
Light chain
Domain
Ag binding site

6. Immunoglobulin structure
Immunoglobulin domains
Variable: VH, VL
Constant:CH, CL

7. Complementarity-determining regions [CDR]
hypervariable loops

8. Antibodies
Antigen binding site
domains, complementarity determining regions (CDR)- hypervariable regions/loops
VL : CDR1, CDR2, CDR3
VH : CDR1, CDR2, CDR3

10. Class and subclass (isotypes) IgM IgG IgA IgD IgE
Antibodies
Class and subclass (isotypes)
Ig Class
Ig subclass
IgM no
IgG
IgG1, IgG2, IgG3, IgG4,
IgA
IgA1, IgA2
IgD
IgE

11. Immunoglobulin structure
Fragments

12. Immunoglobulin structure
Immunoglobulin domain

13. Immunoglobulin superfamily
Immunoglobulin domain

14. Immunoglobulin structure
Antigen binding site

15. Immunoglobulin domains
Antibodies
Immunoglobulin domains
Light chain
Heavy chain
domains VL CL VH CH
IgM 1 4
IgG 3
IgA
IgD
IgE

16. Antigenic Determinants on Immunoglobulins
Name
Localization of Ag determinants
Distribution on
cells / molecules
Idiotype
VH and VL
(in and out CDR)
several B cell clones >> public i.
individual B cell clone >> private i.
Isotype
-class, subclass CH
all members of a species
-type and subtype CL
Allotype
Gm, Am Km
[ in animals also VH,L]
some, but not all members of a species

17. Immunoglobulin Isotypes
IgM (kappa)
IgG1 (kappa)
Importance
Ig levels
B cell tumors
Immunodeficiencies

18. Immunoglobulin Allotypes
IgG1 (kappa)
Person 2
Person 1
Definition - Antigenic determinants
specified by allelic forms of the Ig genes
Importance
-Monitoring bone marrow grafts
-Forensic medicine
-Paternity testing

19. Immunoglobulin Idiotypes
Importance
V-region marker
Regulation of immune responses
IgG1 (kappa)
Person 1
anti-A
IgG1 (kappa)
Person 1
anti-B

20. Antibodies
Function

21. Biological activities of immunoglobulins
Property / activity
IgG1
IgG2
IgG3
IgG4
IgA1
IgA2
IgM
IgE
IgD
Serum level [mg/ml] 9 3 1
0.5
1.5
0.0003
0.03
Half life [days] 23 8 6 5
2.5
1-st in primary response +
Activates classical complement way ++
CH2
+/- -
CH4
Crosses placenta
Present on mature B cells
Binds to mph Fc receptors
Present in secretions
Induces mast-cell degranulation

22. Antibodies
Ig genes

23.                      
                               
Susumu Tonegawa
The Nobel Prize in Physiology or Medicine 1987
„for his discovery of the genetic principle for generation of antibody diversity“

24. Antibody response Cellular lever
Antibodies
Antibody response
Cellular lever

25. B cell activation
Two signals are required for activation
of B cell.
The first signal: binding of Ag to BCR
(surface Ig)
The second signal: binding of Th cell
to B cell.
After activation, B cell differentiate to
- plasma cell >> secretion of Ab
- memory B cells >> secondary response

26. B cell activation
The second signal represents contact between CD40
receptor on B cell and CD40L ligand expressed on Th cells

27. B cell activation
Only activated Th cell is able to provide the second signal for B cells.
Th cells are activated by antigen presenting cell (APC).
Activation of Th requires also two signals (steps):
1st> APC engulf Ag, process Ag and express Ag fragments in the frame of MHCII on the cell surface for TCR (T cell receptor) on T cells.
2nd > APC produce IL-1 which binds to IL-1 receptor on Th cell.

28. Primary and Secondary Responce
Antibodies
Antibody production
Primary and Secondary Responce

29. Primary and secondary response
Primary response
- 1st contact with Ag
IgM
Secondary response
- 2nd contact with Ag
- based on memory B cells
- CLASS SWITCHING
Under the influence of cytokines
B cells switch from IgM production to
IgG and other classes of Ab.
afinity maturation: Ab have high afinity to Ag compared with the afinity of Ab produced in primary response
faster onset of Ab production
higher levels (titers) of Ab
longer persistence of Ab (slower drop
of Ab titers).

30. Monoclonal antibodies
Principle:
1) “Immortalization” of Ag
specific B cell clone by
fusion with myeloma cell.
2) Selection of this clone in HAT
medium.
3) Propagation of Ag specific clone
in vitro or in mice.
____________________________
(Myeloma is a cancer cell “without limitation”
of proliferation)