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Antigen recognition in
adaptive immunity
Mechanism of diversity of antigen receptors
Maturation and selection of B lymphocytes
Maturation and selection of T lymphocytes
Cells display several types
of receptor and each of
them is specific for a
certain ligand
Cells within one clone
display only one type of
receptor specific for a
certain ligand
Antigen receptors on lymphocytes
B
T
cell
cell
Antigens: proteins, polysaccharides,
lipids, nucleic acids, small molecules
Conformational and linear epitops
Complex of peptide-MHC
molecule
on an APC
Linear epitops
N
N
N
C
C
C
C
N
VH
VL
VH
VL
CDR1
CDR1
CDR2
CDR2
CDR3
CDR3
CL
Isotype
a (a1 a2)
IgA(1,2)
g (g1 g2 g3 g4) IgG(1,2,3,4)
V (variable) region
VL i VH
C (constant) region
CL i CH
k
l
CL
CH
CH
d
e
IgD
m
IgM
IgE
Antibodies
• structure
• function
T-cell receptor for antigen (TCR)
structure
Lymphocyte maturation
The Nobel Prize in Physiology or Medicine
1987
"for his discovery of the genetic principle for generation of antibody diversity"
Susumu Tonegawa
Inherited configuration
of gene loci for antigen
receptors
Nasleđena konfiguracija
genskih lokusa za
antigenske receptore
Recombination
and expression
of
immunoglobulin
genes
~100
Mechanisms of creation
of antigen receptor
diversity
54
67
27
61
4
Every day 109 lymphocytes with 107 various
specificities are generated (young)
Phases of B-cell maturation and selection
Phases of B-cell maturation and selection
Phases of B-cell maturation and selection
Phases of B-cell maturation and selection
Phases of B-cell maturation and selection
T-cell maturation in thymus
T-cell maturation in
thymus
Faze u sazrevanju i selekciji T-limfocita
1. TCR gene recombination
a.
eliminates auto-reactive lymphocytes
2. Negative selection
b.
proteins, polysaccharides, lipids
3. TCR recognizes
c.
a and b, or g and d chains
4. Immunoglobulin gene
recombination
d.
peptides within MHC molecule
5. TCR consists of
e.
constant region of heavy chains
6. Antibody has
f.
7. Different isotypes have the same
g.
variable regions of heavy and light
chains
occurs only in thymus
8. Positive selection
h.
provides antibody diversity
9. Antibody can recognize
i.
two identical heavy and two identical
light chains
enables survival of useful lymphocytes
10. Receptors of different clones of B
cells have different
j.
g
a
d 4.____
h 5.____
c 6.____
i 7.____
e 8.____
j 9.____
b 10.____
f
1.____
2.____
3.____