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-COO-

H3N-Ser-Ile-Met-Thr-Arg-Leu-Tyr-Gly..Thr-Glu-Ala-Val-Tyr-Ser-Met-COO-

H3N-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 Editionp. 85

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?

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 Diversity-

Encoded by Very Limit Genome

Heavy and Light Chain Sequence Variations-

Almost Exclusively in only one region

Exactly the same V-region sequences-

End up on different C-region Isotypes.

How is all of this possible?????

Myeloma Cell DNADifferentiated Neoplastic Plasma Cell making a single antibody.

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 oneContinuous 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 Numbers315-443-1870212-345-1775478-367-8903537-503-2078409-159-6309610-970-3970934-620-8122909-603-7023800-620-6021704-590-5307703-725-0153207-502-6671435-431-0890412-830-0048740-592-1954307-620-4450490-501-5672601-909-7002554-891-7712335-592-0944

Immunology and Phone Numbers-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

315-212-478-537-409-610-934-909-800-704-703-207-435-412-740-307-490-601-554-335-

Immunology and Phone Numbers-1870-1775-8903-2078-6309-3970-8122-7023-6021-5307-0153-6671-0890-0048-1954-4450-5672-7002-7712-0944

315-212-478-537-409-610-934-909-800-704-703-207-435-412-740-307-490-601-554-335-

-443--345--367--503--159--970--620--603--620--590--725--502--431--830--592--620--501--909--891--592-

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, C-Genes

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

From Kuby Immunology, 4th Ed.Upper Half of Table: Human DataLower Half (not shown): Mouse Data.

6 Edition V,D,J segment numbers are slightly different

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.

B-Cell Differenatiation

Please put away all notes and devices other than your XR transmitter.

No consulting or reading notes is permitted. No online searches.This are graded response questions.

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