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IgG
IgM
IgA IgD IgE
Clonal Selection
• Bone marrow gives rise to B
cells.
• Mature B cells migrate to
lymphoid organs.
• A mature B cells recognizes
epitopes.
Hallmarks
of the
Immune Response
• Self/Non-self Discrimination
• Memory
• Specificity
A. Self/non-self discrimination - One characteristic feature
of the specific immune system is that it normally
distinguishes between self and non-self and only reacts
against non-self.
B. Memory - A second feature of the specific immune
response is that it demonstrates memory. The immune
system "remembers" if it has seen an antigen before and it
reacts to secondary exposures to an antigen in a manner
different than after a primary exposure. Generally only an
exposure to the same antigen will illicit this memory
response.
C. Specificity - A third characteristic feature of the specific
immune system is that there is a high degree of specificity in
its reactions. A response to a particular antigen is specific for
that antigen or a few closely related antigens
T-independent Antigens
B cell
Figure 17.17
Self-tolerance
• Body doesn't make Ab
against self
• Clonal deletion
–The process of
destroying B and T cells
that react to self antigens
T-Dependent Antigens
Figure 17.16
Clonal Selection
Cellular Events in 1o Response to
T-dependent Ags
• Lag
– Clonal selection
• Log
1o Ag
– IgM
– Class switching
• Stationary
• Decline
• Memory Cell Pool
IgM
IgG
Memory Cells
Cellular Events in 2o Response to
T-dependent Ags
• Lag phase
– Virgin cells
– Memory cells
Virgin B cell
• Log phase
IgG
– Pool size
– IgG, IgA or IgE
• Stationary
• Decline
– Sustained
production
IgM
Memory
Pool
Memory
Cells
IgG
Memory
Cells
Memory T cells
• T Cells
– Virgin cells
– Memory cells
Virgin cell
• Th cells
Th
Th
– Cytokines
• Long Term
Memory
Memory
Pool
Memory
Cells
Th
Memory
Cells
Animation of cell selection
TORTORA • FUNKE
• CASE
Immunoglobulin Genetics
IgG
IgM
IgA IgD IgE
How many types of Abs???
• 100 Millions
8
• 100,000,000 = 10
Immunoglobulin Genetics
History
• Same C region could associate with many V
regions
– IgG Ab with different specificities
• Same V region could associate with many C
regions
– Same idiotype on IgG and IgM Ab
• V and C regions coded for by separate genes
Light Chain Gene Families
Germ line gene organization
Lambda light chain genes; n=30
V1
L
P
L
V2
P
L
Vn
J
1
P
C
1
J
2
E
J
3
C
2
E
C
3
J
4
E
C
4
E
Kappa light chain genes; n=300
L
P
V1
L
P
V2
L
P
Vn
J 1
J 2
J 3
J 4
J 5
C
E
Light Chain Gene Families
Gene rearrangement and expression
L
V 1
P
L
V 2
P
V n
L
P
L
V 1
P
L
V 2 J4
J 5
P
L
V J
DNA
C
Primary transcript
RNA
L V J C
mRNA
Translation
DNA
C
E
E
RNA Processing
C
E
DNA Rearrangement
Transcription
J 1 J 2 J 3 J 4 J 5
RNA
L V J C
Protein
Transport to ER
V J C
Protein
V
C