5. agrc genetic
TRANSCRIPT
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Immunoglobulin Genetics
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Immunoglobulin GeneticsHistory
• 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
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ight Chain Gene !amiliesGerm line gene organi"ation
J 1 C 1
E
J 2 C 2
E
J 3 C 3
E
J 4 C 4
EP
L V1
P
L Vn
P
L V2
Lambda light chain genes; n=30
P
L V 1
P
L V n
P
L V 2 J
2 J
3 J
5 C
E
J
1 J
4
Kappa light chain genes; n=300
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ight Chain Gene !amiliesGene rearrangement and e#pression
L V 1 L V
nL V
2 J
2 J
3 J
5 C
J
1 J
4
DNAP PP E
P P E
L V 1 L J
5 C
V 2 J
4
DNA
DNA Rearrangement
V CJ
V C
Protein
Transport to ER
Protein
TranslationCL V J
E
L V CJ
RNA
Transcription
Primary transcript
CL V JRNA Processing
RNAmRNA
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Hea$y Chain Gene !amilyGerm line gene organi"ation
Introns separate exons coding for H chain domains
Heav chain genes; Vn=1000! "n=1#
P
L V1
P
L Vn
P
L V2 D2 D3D1 Dn
C
C
C 3 C
C 2C 1 C 4 C 1 C
2
J2 J3 J5J1 J4
E
C1 C2 C3 C4
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Hea$y Chain Gene !amilyGene rearrangement and e#pression
P
L V1
P
L Vn
P
L V2 D2 D3D1 Dn C
C J2 J3 J5J1 J4
E
DJ rearrangement
P
L Vn
P
L V1
P
L V2D2
D1 C
C J5
J4
EDNA
VDJ rearrangement
D2 C
C J5
J4
EP
L V1
P
LV2
DNA
Transcription
D2 C
C J5
J4
E
LV2
RNAPrimary transcript
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Hea$y Chain Gene !amilyGene rearrangement and e#pression
EPrimary transcript
E
J4D2V2 C
C
J5L C
C
J5L D2 J4V2
RNA Processing
An
mRNA !or C
C
L DJV C
L DJV
An
mRNA !or C
Translation
C
"ea#y c"ain
C
L DJV C
L DJV
C
"ea#y c"ain
Transport to ER
C
"ea#y c"ain
V C
C
DJV C
DJV
C
"ea#y c"ain
V C
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Class Switching
• %&A
rearrangement
– Antigendependent
– Switch site
– Same V%'
– (H cyto)ines
L
3 2
1 4 1 2
P
L V DJ
$ $ $ $ $ $ $ $
P
L
$
1 2
$ $
Primary Transcript %g&or %gD
Primary Transcript%gE
RNA
DNA
DNA
DNA Rearrangement
L
V DJ
V DJV DJ
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Mechanism of %&A
*earrangements
• *ecombination
signal se+uences
,*SS- – &onmer
– Heptamer
– . or / turn signals
$ %ag&1 and %ag&2
L V
2
J C
1
Lam'(a lig"t c"ains
L V
1
J C
2
)appa lig"t c"ains
ea#y c"ains
L V
2
J C
211
D
eptamer
CACA*T*
*T*TCAC
Nonamer
ACAAAAACC
T*TTTTT**
23 'p
23 'p
T+o t,rn
R$$
2
Nonamer
**TTTTT*T
CCAAAAACA
eptamer
CACT*T*
*T*ACAC
12 'p
12 'p
-ne t,rn
R$$1
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0rder of Ig Gene 1#pression
.
/
ea#y c"ain gene
VDJ recom'ination
Pro(,cti#e rearrangement 0
es
No
Transcri'etranslate
1st
2n(
or
Apoptosis
Progenitor cell
Pre cell
ea#y c"ain
Paternal&aternal
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0rder of Ig Gene 1#pression
.
/
Lig"t c"ain gene
VJ recom'ination
Pro(,cti#e rearrangement 0
es
No
Transcri'etranslate
Lig"t c"ain
4 t"
Apoptosis
1st /
2n( /3r( /
4t" /
or
Pre cell
&at,re cell
.
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0rder of Ig Gene 1#pression
1#plains2
• 3hy an indi$idual 4 cell only produces
one )ind of Ig with one )ind of hea$y and
one )ind of light chain
• 3hy an indi$idual 4 cell only ma)es
antibodies of one specificity
• 3hy there is allelic e#clusion
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0rigin of Antibody %i$ersityHistory
• %efinition – %i$ersity ,repitoire- is the total
of all the Ab specificities that an organism
is capable of e#pressing
• (heories
– Germ line theory
– Somatic mutation theory
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0rigin of Antibody %i$ersityCurrent concepts
• Multiple V genes
$ V&' and V&"&' (oining
$ ')nctional diversit
$ * region insertions
+ ,mino acid
se-)ences notencoded in the germ
line
D region
T **C CC
Pro Trp
C C C C C C
V gene
T **
D region
C C C C C C
V gene
T **
C **C CC
Pro Arg
C C C C C C
V gene
T **
D region
C *CC CC
Pro Pro
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/./,,/.
/./,,/./ .
rea "*,
/d/ adds n)cleotides
Ligate
* region insertion Intron
'"
'
'
'
"
"
"
.eneration of * region insertions
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0rigin of Antibody %i$ersityCurrent concepts
• Multiple V genes
$ V&' and V&"&' (oining
$ ')nctional diversit
$ * region insertions
$ omatic m)tation
$ ombinatorial association
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Generation of %i$ersity
B cell receptor(Immunoglobulin)
Heavy Light
V gene segments 1000 300
D gene segments 15
! gene segments " "
# region insertion $$
!unctional %iversity $$$ $
&omatic mutation $ $
V ' D ' !
1000 ' 15 ' "
V ' !
300 ' "otal ' 10
" 1*+ ' 10
3
,ombinatorial association -*+ ' 10-
$ ,g independent process $ lonal selection
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( Cell Antigen *eceptor
• Heterodimer of an and a chain
• Gene structure and e#pression of the chain is
analogous to the immunoglobulin light chain
• Gene structure and e#pression of the chain isanalogous to the immunoglobulin hea$y chain
• &o somatic mutation in ( cells
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(he germline organi"ation of the
human (5cell receptor 6 and 7 loci
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( cell receptor 6 and 75chain gene
rearrangement and e#pression
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