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Organization & Expression of Immunoglobulin Genes

Hugh B. Fackrell

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Organization & Expression of Immunoglobulin Genes

Assigned ReadingContent Outline

Performance ObjectivesKey terms

Key Concepts

Short Answer Questions

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Assigned Reading Chapter: 7 pp 165-194 Janis Kuby’s Immunology 3rd Ed

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Content Outline Genetic models Multigene

Organization of Immunoglobulin Genes

Variable-Region Gene Rearrangements

Generation of Antibody Diversity

Class Switching in C region genes

Expression of Ig Genes

Regulation of Ig-Gene Transcription

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Genetic models Germ line vs somatic mutation

model Dryer Bennett: Two gene model Verification

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Multigene Organization of Immunoglobulin Genes

lambda chain multigenes kappa chain multigenes heavy chain multigenes

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Variable-Region Gene Rearrangements

V-J rearrangements of light chains V-D-J rearrangements of heavy

chains

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Mechanisms recombination signal sequences enzymatic joining of gene

segements RAG-1 RAG-2 Defects Productive vs non productive gene

rearrangements Allelic exclusion

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Generation of Antibody Diversity

multiple germ line gene segments combinatorial V-J & V-D-J joining junctional flexibility P-nucleotide addition N-nucleotide addition Somatic hypermutation Association of light & heavy chains

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Class Switching in C Region Genes

Expression of Ig Genes Differential processing of RNA

transcripts of heavy chains Membrane bound vs secreted Ig Coexpression of IgM & IgD Synthesis, assembly and secretion

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Regulation of Ig-Gene Transcription

DNA rearrangement Inhibition by T Cells

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DONE!!!DONE!!!

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Performance Objectives

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Key Terms allelic exclusion, class switching, combinatorial freedom of chain

association,comibinatorial association of

gene segments, Constant (c) gene segments, Diversity (D) gene segemtns,

Palindromes, acceptor junctions, donor junctions, enhancers, exons,

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7-9 rule, 12-23 rule, Germline theory, somatic theory, imprecise DNA rerangement,

Insertion of random N regions, introns, Joining (J) gene segments,

junctional diversity, leader sequence, Membrane (M) exons), n regions

promotors, recognition sequences, spacer sequences, somatic hypermutation,

switch recombination. switch (S) regions, variable(V) gene segments

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Key Concepts Describe how the number and

organization of immunoglobulin gene segements or exons contribute to the generation of antibody diversity

Draw the organization of Kappa light chain genes.

Draw the organization of Lambda light chain genes.

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Draw the organization of heavy chain genes.

Describe the V-J joining for light chain genes in terms of the 7-9 and the 12-23 rules

Describe the V-D-J joining of heavy chain genes in terms of the 7-9 and the 12-23 rules.

Explain how allelic exclusion leads to cells that produce immunoglobulins with a single antigen binding site.

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Describe how transcription controls immunoglobulin gene expression

Describe at least four mechanisms that contribute to antibody diversity

Describe the coexpression of IgM and IdD in terms of RNA processsing

Describe the mechanisms for class switching Correlate B cell differentiation with

immunoglobulin gene rearrangements

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Short Answer Questions

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Why is it important to have antibody diversity? Differentiate between the germline theory and the

somatic theory of generation of antibody diversity. How are BOTH germline and somatic mechanisms

sources of antibdoy diversity? Why did the amino acid sequencing of antibody light

chains lead Dryer and Bennet to abandon the one gene- one polypeptide theory and propose that two genes code for a single polypeptide?

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Describe Tonagawa's approach to answering Dreyer and Bennett's hypothesis that two genes code for a single polypeptide.

In addition to showing that DNA seqments come together to form a functional antibody gene, Tonagawa's experiments showed two other things. What were they?

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The phrases "race car", "Madam I am Adam" and "sex at noon taxes" represent pallindromes in the english language.

What are pallindromes in the genetic code and what is their importance in V region construction?

What are the two DNA recombinational events required to assemble a functional heavy chain V region gene?

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The two DNA recombinational events required to assemble a functional heavy chain V region gene, are governed by the 7-9 and the 12-23 rules. Explain.

Discuss four mechanisms that contribute to antibody diversity.

Describe the differential splicing of RNA that progresses from membrane bound IgM to secreted IgM.

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Explain how a particular B cell can secrete different antibody isotypes, yet remain specific for the same epitope.

What are the two stages of class switching?

Dicuss allelic exclusion; what it is and how it is regulated.

List in correct chronological order the events leading to the synthesis of a Kappa light chain and its incorporation into an antibody molecule.

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List in correct chronological order the events leading to the synthesis of a Gamma chain and its incorporation into an antibody molecule.