Aims Gene rearrangement and class switching of B-cell Igs.

Slides:



Advertisements
Similar presentations
TODAY B CELL DEVELOPMENT.
Advertisements

How is antibody diversity generated? Two early theories: Germline hypothesis The genome contains many loci encoding antibody molecules. B cells express.
Immunoglobulin Gene Organization and Expression W. Robert Fleischmann, Ph.D. Department of Urologic Surgery University of Minnesota Medical School
Antibody Diversity.
Generation of diversity in lymphocyte antigen receptors Jan. 31, Feb. 2 & 5 Chapter 4.
Outline Immunoglobulin Superfamily Antigen Recognition Members:
Structure of Class II MHC (continued) 3.Transmembrane region – stretch of hydrophobic amino acids spanning membrane 4.Cytoplasmic region – contains sites.
Micro 297 Graduate Immunology Lecture 15 Development of B Lymphocytes I Generation of Antibody Diversity Thursday August 14, 2003 Michael Wolcott READING.
Lecture 5 Antibody genes I Problem of the generation of diversity V(D)J recombination Surface immunoglobulin B lymphocyte development Heavy chain class.
Immunoglobulin Genetics. Problem…the immune system makes over one billion different antibody proteins In 1950’s: central dogma stated DNA—to RNA—to protein.
Antibodies and T Cell Receptor Genetics 2011
Chapter 14 B Lymphocytes. Contents  B cell receptor and B cell complex  B cell accessory molecules  B cell subpopulations  Functions of B cells 
ANTIBODY STRUCTURE AND THE GENERATION OF B-CELL DIVERSITY
Organization & Expression of Immunoglobulin Genes
Sections to Skip for Ch 2 Figure Enzyme digestion of Ab’s Monoclonal Antibodies Fig 2.12 & 2.13.
Diversification of antibodies after B-cells encounter antigen Alternative splicing Somatic hypermutation Ig. class switch.
H. HogenEsch, 2005 Antibody structure and function Parham – Chapter 2.
Immunology 6 Specificity 8. Specificity of immunoglobulin molecule on B cell – BCR of receptor on T cell – TCR is defined and produced before their exposition.
Chapter 24 Immune diversity Introduction 24.2 Clonal selection amplifies lymphocytes that respond to individual antigens 24.3 Immunoglobulin genes.
CHAPTER 23 Molecular Immunology.
Principle of Single Antigen Specificity Each B cell contains two copies of the Ig locus (Maternal and Paternal copies) Only one is allowed to successfully.
Organization and Expression of Immunoglobulin Genes.
B-CELL DIFFERENTIATION IN THE PERIPHERY SOMATIC HYPERMUTATION
OF THE VARIABILITY OF ANTIGEN RECOGNIZING RECEPTORS
Chapter 4 and 5 Ig study questions (Th): How does the immune system recognize a diverse universe of possible antigens? How do antibodies simultaneously.
B Cell Activation and Antibody Production Lecture 15.
Antibodies & Antigens1 Antibodies Also chap 5 pp Self-Test Questions: Chap 4: all Chap 5: D all MolnQuiry.
Epigenetic control of Gene Regulation Epigenetic vs genetic inheritance  Genetic inheritance due to differences in DNA sequence  Epigenetic inheritance.
The genetic basis of antibody structure
Chapter 4 and 5 Ig study questions (Tu): Can you name at least four ways in which CSR and V(D)J recombination differ? What are the substrates (what genes,
Ch4. Antibody Structure and the Generation of B-cell diversity.
REVIEW: IMPORTANT INFORMATION TO DATE ABOUT ===> B cells ANTIBODY ABOUT ===> B cells & ANTIBODY
Ig Polypeptides Are Encoded by Multiple Gene Segments LIGHT CHAIN
Chapter 9 T-cell Receptor Dr. Capers. Kuby IMMUNOLOGY Sixth Edition Chapter 9 T-Cell Receptor Copyright © 2007 by W. H. Freeman and Company Kindt Goldsby.
Chapter 7 Organization and Expression of Immunoglobulin Genes
Rearrangement The normal process by which antibodies and T cell receptors are made.
Lecture 1: Immunogenetics Dr ; Kwanama
Lecture 2: Antibody Diversity
Chapter 13 Lymphocyte Maturation and Antigen Receptor Expression
ADAPTIVE IMMUNITY. Adaptive immunity Specific Slow during the primary response, but very fast during the secondary responses memory.
Immune system Haixu Tang School of Informatics. Human lymphoid organs.
A a Activated B-cell Mature naive B-cell Memory B-cell B-CELL DIFFERENTIATION IN THE PERIPHERY SOMATIC HYPERMUTATION ISOTYPE SWITCH Ag.
IgGs: Somatic recombination and combinatorial diversity n Immune system - recognition of “self” vs. “non-self” n Hallmarks of immune response –specificity.
Antigen recognition in adaptive immunity Mechanism of diversity of antigen receptors Maturation and selection of B lymphocytes Maturation and selection.
The key experiment of Nobumichi Hozumi and Susumu Tonegawa
Chapter 5 Organization and Expression of Immunoglobulin Genes Dr. Capers.
Humoral immunity Antibody structure Antibody diversity
A a Activated B-cell Mature naive B-cell Memory B-cell B-CELL DIFFERENTIATION IN THE PERIPHERY SOMATIC HYPERMUTATION ISOTYPE SWITCH Ag.
Adaptive Immunity Central objective: Protect against foreign invaders memoryCreate memory of invasion to prevent recurrent infection specificResponse.
Antibody Diversity. Immunoglobulin: antibody Antibody response: B cells, with the help of T cells, produce antibody to antigen, preserve the ability to.
Immunoglobulin Genetics. Problem…the immune system makes over one billion different antibody proteins In 1950’s: central dogma stated DNA—to RNA—to protein.
Immunoglobulin Genetics
IMMUN 441 Week 4 AC Quiz Section
Immunoglobulin Gene Rearrangement
The genetic Basis of Ab Structure
B cells I. Differentiation of B cells in Bone marrow II
Immunogenetics.
Immunoglobulin Expression and the Role of Antigen in
LESSON 3: ANTIBODIES/BCR/B-CELL RESPONSES
Immunogenetics Lecture 3: TcR.
Antibody production and B cell differentiation
Immunoglobulins (2 of 2) Ali Al Khader, MD Faculty of Medicine
The Differentiation of Vertebrate Immune Cells
What does the word Promoter mean?
The Differentiation of Vertebrate Immune Cells
Immunoglobulins (2 of 2) Ali Al Khader, MD Faculty of Medicine
Molecular mechanisms of IgE regulation
Generation of antibody diversity
Antigen recognition in adaptive immunity
Immunogenetics Genetic Changes that Provide for Homology and Diversity Among Immune System Proteins.
Presentation transcript:

Aims Gene rearrangement and class switching of B-cell Igs. Lecture #9 Aims Gene rearrangement and class switching of B-cell Igs. T cell receptors- What are they and where do they fit into immunology? Gene rearrangement to generate diversity Readings: Abbas & Lichtman, Chapters 4 & 7

Human Immunoglobulin Loci Heavy Chain Light Chain Abbas & Lichtman’s Basic Immunology 4-9

Heavy Chain Synthesis Variable (VH) segments Diversity (DH) segments Vn 5’ 3’ Germline DNA J1-n D1-n Ce Ca Cg Cd Cm Variable (VH) segments Diversity (DH) segments Joining (JH) segments Conserved (CH) segments Similar to Abbas & Lichtman’s Basic Immunology 4-10

Heavy Chain Synthesis 5’ 3’ V1 V2 Vn Germline DNA J1-n D1-n Ce Ca Cg Cd Cm Rearranged B cell DNA Intervening DNA between the D and J segments is looped and cut out. Similar to Abbas & Lichtman’s Basic Immunology 4-10

Heavy Chain Synthesis 5’ 3’ Ce Ca Cg Cd Cm V1 V2 Vn Rearranged B cell DNA Intervening DNA between the V and D segments is looped and cut out. Similar to Abbas & Lichtman’s Basic Immunology 4-10

Heavy Chain Synthesis 5’ 3’ Ce Ca Cg Cd Cm V1 V2 Rearranged B cell DNA Primary RNA transcript The gene is transcribed resulting in a primary RNA containing the VHDHJH segment, the remaining J segments and only the Cm and Cd segments. Similar to Abbas & Lichtman’s Basic Immunology 4-10

Heavy Chain Synthesis 5’ 3’ Cd Cm V2 Primary RNA transcript mRNA transcript The transcript is processed and the introns and Cd sequences are removed. The resulting mRNA contains the Cm segment and will code for an IgM. Similar to Abbas & Lichtman’s Basic Immunology 4-10

Heavy Chain Synthesis mRNA transcript NH2 COOH Cm V2 m heavy chain polypeptide 5’ 3’ The mRNA is translated by ribosomes into m chain. Adapted from Abbas & Lichtman’s Basic Immunology 4-12

Light Chain Synthesis Variable (Vk) segments Joining (Jk) segments Vn Ck J1-n 3’ 5’ Germline DNA Variable (Vk) segments Joining (Jk) segments Conserved (Ck) segment 2 isotypes l (40%) and k (60%)

Light Chain Synthesis Germline DNA V1 V2 V3 Vn Ck J1-n 3’ 5’ Rearranged B cell DNA V1 V2 V3 Ck 3’ 5’ Intervening DNA between the V and J segments is looped and cut out. Similar to Abbas & Lichtman’s Basic Immunology 4-10

Light Chain Synthesis V3 Ck 3’ 5’ Primary RNA transcript V1 V2 Rearranged B cell DNA The B cell transcribes a segment of DNA into a primary RNA transcript that contains a long intervening sequence of J segments and introns. Similar to Abbas & Lichtman’s Basic Immunology 4-10

Light Chain Synthesis V3 Ck 3’ 5’ Primary RNA transcript V3 Ck 3’ 5’ mRNA transcript This RNA transcript is processed into mRNA by splicing the exons together. Similar to Abbas & Lichtman’s Basic Immunology 4-10

Light Chain Synthesis V3 Ck 3’ 5’ mRNA transcript COOH NH2 k chain polypeptide The mRNA is translated by ribosomes into k chains. Combines with heavy chain to make IgM.

Light Chain Synthesis IgM NH2 COOH m heavy chain polypeptide Ck COOH NH2 k chain polypeptide Cm V2 m heavy chain polypeptide IgM Abbas & Lichtman’s Basic Immunology 4-12

mRNA Splicing 5’ 3’ IgD mRNA Primary heavy chain RNA transcript Cd Cm V2 IgD mRNA IgM mRNA Abbas & Lichtman’s Basic Immunology 4-12

Ig Class Change All classes of immunoglobulin use the same set of variable region genes (ie V-D-J). All that changes is the constant region of the heavy chain. Abbas & Lichtman’s Basic Immunology 7-10

Ig Class Change Involves a switch sequence upstream of the constant region gene segments. Recombination occurs between the Sμ recombination region and a downstream switch region (Sg). The intervening region containing genes for IgM and IgD in this instance is looped out and then cut, with deletion of the intervening regions and joining of the two switch regions. Adapted from Abbas & Lichtman’s Basic Immunology 7-10

Ig Class Change Class change occurs upon B cell activation and maturation. Requires signals from ____________________________ (CD3+, CD4+, CD8-). Binding of receptors (CD40 ligand) Cytokines Abbas & Lichtman’s Basic Immunology 7-9

Mechanisms of Antibody Diversity Combinatorial diversity Multiple germ line V genes recombining with J and D segments. Junctional diversity Imprecision in V-J and V-D-J recombinations (N-region diversity) N-nucleotide additions (N-region diversity) Note addition is done without a template. Somatic point mutation Assorted heavy and light chains

Combinatorial Diversity Possible combinations of V-D-J and V-J germ line gene segments. Abbas & Lichtman’s Basic Immunology 4-11

Junctional Diversity (N- region diversity) V segment J segment G T A Germ line DNA Arg Ser Tyr Trp Protein Recombined DNA Changes in nucleotide sequence at junctions of V, D, and J segments. Two types of changes Exonuclease removal of nucleotides. Random addition of nucleotides by terminal deoxyribonucleotidyl transferase (TdT).

Junctional Diversity (N- region diversity) V segment J segment G T A Germ line DNA Arg Val Trp Protein Recombined DNA Changes in nucleotide sequence at junctions of V, D, and J segments. Two types of changes Exonuclease removal of nucleotides. Random addition of nucleotides by terminal deoxyribonucleotidyl transferase (TdT).

Junctional Diversity (N- region diversity) V segment J segment G T A Germ line DNA Arg Leu Val Trp Protein Recombined DNA Changes in nucleotide sequence at junctions of V, D, and J segments. Two types of changes Exonuclease removal of nucleotides. Random addition of nucleotides by terminal deoxyribonucleotidyl transferase (TdT).

Surface vs. Secreted Primary RNA transcript 5’ 3’ Cm V2 Soluble IgM mRNA sIgM Ts Poly A Tm Membrane IgM mRNA mIgM Which poly A site is transcribed determines whether the protein is surface or secreted.

Membrane Bound Ig IgM or IgD Lecture #9 Membrane Bound Ig IgM or IgD Associated with a heterodimer of Iga and Igb. Activation of the BCR results in activation of Iga and Igb leading to cytoplasmic signaling and B cell activation B cell receptor (BCR) complex Iga Igb Figure 8.8 B-cell activation is similar to T-cell activation. If membrane Ig becomes cross-linked (e.g. by a T-independent antigen), tyrosine kinases, including Lck, Lyn, Fyn and Blk, become activated. They phosphorylate the ITAM domains in the Igα and Igβ chains of the receptor complex. These can then bind another kinase, Syk, which activates phospholipase C. This acts on membrane PIP2 to generate IP3 and diacyl glycerol (DAG) which activates protein kinase C. Signals from the other kinases are transduced to activate nuclear transcription factors.

Antibody Kinetics __________________________ is the tendency of antibody to form stable complexes with an antigen + Ag

Antibody Kinetics _________________________ is the strength in which a multivalent antibody binds a multivalent antigen. Y IgM IgG Ag

T Cell Receptor Present on a majority of T cells both CD4+ and CD8+. Heterodimeric molecule. Linked by a disulfide bond. Generated by 4 sets of genes a and b genes are expressed in a majority of peripheral T cells. g and d are expressed on a minority of thymic and peripheral T cells (10%). Binds to the peptide-MHC complex.

T Cell Receptor 2 a chains 2 b chains Associated with CD3 2 z chains Variable domain Conserved domain CD3 2 a chains 2 b chains Associated with CD3 2 e chains 1 d chain 1 g chain 2 z chains Adapted from Roitt’s Immunology 4-6

T-Cell Receptor Loci Adapted from Abbas & Lichtman’s Basic Immunology 4-9

T Cell Receptor Diversification Vn 5’ 3’ Germline a DNA J1-n Ca J11-n D1 Cb1 Germline b DNA J21-n Cb2 D2 Variable (VH) segments Diversity (DH) segments Joining (JH) segments Conserved (CH) segments

T Cell Receptor Diversification J1-n 5’ 3’ V1 V2 Ca Vn Germline a DNA J11-n J21-n D1 D2 5’ 3’ V1 V2 Vn Cb1 Cb2 Germline b DNA Recombination between V, D, and J gene segments. a and g chains contain V and J gene segments. b and d chains contain V, D, and J gene segments. Similar to Ig.

Comparison of TCR and Ig Ig binds to proteins, polysaccharides, Lipids, and nucleic acids, while TCR only binds peptides in MHC. Forms of Antigen Recognized Diversity Antigen Recognition Mediated by Signaling functions Mediated by Effector functions Mediated by Abbas & Lichtman’s Basic Immunology 4-1

Antigen Recognition Ig binds antigen all by itself, while TCR needs CD4 or CD8 to simultaneously bind. Antigen Binding Region Structure of antigen recognized Affinity of antigen binding On-rate and Off-rate Accessory molecules Involved in binding Abbas & Lichtman’s Basic Immunology 4-7

Next Time T cell maturation Cell-mediated immune responses (CMI) Humoral immune responses B cell activation Readings: Abbas & Lichtman, Chapters 5 & 6

Objectives Describe the structure and synthesis of the various immunoglobulin Heavy and Light chains, and T-cell receptors. V, D, J, C Segments Describe the process of immunoglobulin class change. Describe the mechanisms of antibody diversity. Combinitorial vs Junctional Surface vs Secreted Know the difference between affinity and avidity. Compare and contrast immunoglobulins and T-cell receptors.