Transcript AbGenes

Genetics in the Generation of
Antibody Diversity
Folder Title: AbGenesNoTP
Updated: October 09, 2014
Chapter Seven, 7th Edition:
“Organization and Expression of Lymphocyte Receptor Genes”
Includes Immunoglobulin and T-Cell Receptor Genetics
Questions About B-Cell Responses
Biochemical Questions:
1. How can Immunoglobulins recognize so many different
epitopes?
2. What does an antibody protein look like?
3. How do specific antibodies work as proteins binding so many
different specific antigenic determinants?
Representation of Sequence Comparisons Among Light Chains
from Antibodies with Three Different Antigen Specificities
H3N-Ser-Val-Ile-Thr-Gly-Gly-Tyr-Ala... Thr-Glu-Ala-Val-Tyr-Ser-Met-COOH3N-Ser-Ile-Met-Thr-Arg-Leu-Tyr-Gly..Thr-Glu-Ala-Val-Tyr-Ser-Met-COOH3N-Thr-Gly-Gly-Thr-Lys-Leu-Tyr-Ile..Thr-Glu-Ala-Val-Tyr-Ser-Met-COO-
Variable Amino Terminal Half
Conserved Carboxyl Terminal Half
(Positions 1 to 107)
(Positions 108 - 214)
LiteComp
See Figure 4-6,
Kuby 6th Edition
p. 85
Questions About B-Cell Responses
1.
Biochemical Questions:
How can Immunoglobulins recognize so many different epitopes?
2.
3.
What does an antibody protein look like?
How do specific antibodies work as proteins binding so many different specific
antigenic determinants?
Genetic Question:
How can this diversity of structure leading to enormous diversity
of function be coded and controlled by a very limited host
genome?
How can we have “one gene - one polypeptide” and make a
virtually limitless selection of polypeptides?
Problems for Genetics in Generating
Antibody Sequence Diversity
Vast Sequence DiversityEncoded by Very Limit Genome
Heavy and Light Chain Sequence VariationsAlmost Exclusively in only one region
Exactly the same V-region sequencesEnd up on different C-region Isotypes.
How is all of this possible?????
Differentiated Neoplastic
Plasma Cell making a single
antibody.
Myeloma Cell DNA
Myeloma Cell Conclusions
Variable and conserved
regions of light chain are
linked in the differentiated
end-product cell line
DNA coding for the mRNA for
the light chain is all in one
Continuous sequence as for
any gene for any protein.
Embryonic Mouse Cell DNA
Variable and conserved
regions of light chain are
not linked originally in the
stem cell lineage!
Immunology and Phone Numbers
315-443-1870
212-345-1775
478-367-8903
537-503-2078
409-159-6309
610-970-3970
934-620-8122
909-603-7023
800-620-6021
704-590-5307
703-725-0153
207-502-6671
435-431-0890
412-830-0048
740-592-1954
307-620-4450
490-501-5672
601-909-7002
554-891-7712
335-592-0944
Immunology and Phone Numbers
315212478537409610934909800704703207435412740307490601554335-
-443-1870
-345-1775
-367-8903
-503-2078
-159-6309
-970-3970
-620-8122
-603-7023
-620-6021
-590-5307
-725-0153
-502-6671
-431-0890
-830-0048
-592-1954
-620-4450
-501-5672
-909-7002
-891-7712
-592-0944
Immunology and Phone Numbers
315212478537409610934909800704703207435412740307490601554335-
-443-345-367-503-159-970-620-603-620-590-725-502-431-830-592-620-501-909-891-592-
-1870
-1775
-8903
-2078
-6309
-3970
-8122
-7023
-6021
-5307
-0153
-6671
-0890
-0048
-1954
-4450
-5672
-7002
-7712
-0944
Kappa Chain DNA: Vk’s
This and the next two slides deal with Kappa Light Chain
DNA. Human Kappa DNA was 40 different “V” region genes
to work with, and 5 “J” region genes.
Lambda light chain DNA works the same way except that the
Human Lambda light chain works with 30 “V” regions and 4
“J” region genes.
Kappa Chain: K-J- C
Complete Kappa Chain
Heavy Chain Dna: VH’s, CGenes
This and the next two slides deal with Heavy
chain DNA. Human heavy chain DNA has 51
“V” region genes to work with, 27 “D”
(diversification) region genes, and 6 “J” (joining)
region genes.
Coupling a VH option with DH option and a JH option to a Cu gene
sequence would give a Mu Heavy chain isotype with a specific
antibody recognizing specificity.
Coupling that exact same VH-DH-JH genetic information to Cd or
Cg or Ce or Ca Heavy chain isotype gene would give the exact
same antigen specificity on a different isotype.
We would have Isotype Switching
Complete Heavy Chain
Additional sequence diversity estimated at several orders of magnitude (i.e. perhaps
1000-fold) is generated by junctional flexibility, nucleotide addition, and somatic
hypermutation. This allows for an estimated 100 million to a billion different possible
antibody seuquences in humans.
From Kuby Immunology, 4th Ed.
Upper Half of Table: Human Data
Lower Half (not shown): Mouse Data.
6 Edition V,D,J segment numbers are slightly different
B-Cell Differenatiation
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