2017 Arizona United Rheumatology Alliance Annual Meeting
Overview of the Immune System and Memory B-cell Activity in RA
Gregg J. Silverman, MD Professor of Medicine and Pathology Director, Laboratory of B-cell Immunobiology NYU School of Medicine New York, NY
Learning Objectives
• Discuss how the layers of the immune system are assembled and interconnected. • Briefly review the ancient innate system, components and properties. • Discuss the special abilities of the adaptive immune system. • Review B lymphogenesis. • Discuss how antigenic selection molds the B cell repertoire. • Brief overview of the immunology of Rheumatoid Arthritis and associated ectopic lymphoid tissue and GCs. • Discuss the effect of therapy on disease-associated B cell memory and circulating ACPA.
Organization of the Immune System
Anatomical and Bad outer world Low Physiological Barriers stomach pH Lysozyome in tears and saliva
Ciliary Innate Immunity clearance Host defense peptides NLR’s TLR’s Dendritic cells Complement Adaptive Immunity T cells Intact skin Neutrophils B cells 0-4 hours 4-96 hours Late > 96 hours Synchronous Functioning: Features of the Innate and Adaptive Immune Systems1,2
INNATE ADAPTIVE . Rapid . Delayed . Antigen-nonspecific . Antigen-specific pathogen recognition pathogen recognition . Activates the adaptive . Confers long-lasting immune system immunity
Macrophage T cell Dendritic cell IL-1β B cell TNF-α IL-6 Neutrophil Complement Plasma cell Antibodies
Abbreviations: IL, interleukin; TNF, tumor necrosis factor. References: 1. Murphy K, ed. Janeway’s Immunobiology. 2012. 2. Chaplin DD. J Allergy Clin Immunol. 2010;125(2 suppl 2):S3-S23. What is the Function of Innate Immunity?
1. Limit the extent of the initial microbial infection a) Phagocytosis, macrophage activation b) Neutrophil activation, degranulation c) Release of antimicrobial peptides d) Cytokine, chemokine production 2. Prime the adaptive immune system a) Antigen presentation b) Expression of costimulatory molecules c) Cytokine, chemokine production 3. Wound repair and tissue remodeling a) DAMPs = Danger-associated Molecular Patterns Immune Response - Innate
• All of these defenses are without MEMORY • Early response ( minutes to 3-5 days) consisting of CELLULAR and SOLUBLE elements • Expressed by GERMLINE encoded receptors • Does not recognize every antigen but rather highly conserved structures DAMP The Roles of Innate Cell Types: Neutrophils, Monocytes, Macrophages, and Dendritic Cells1,2
INNATE Dendritic cell Inflammatory Antimicrobial functions: . stimulus Neutrophils - Phagocytose and kill extracellular pathogens
IL-15 - Release proinflammatory IL-12 factors and antibacterial proteins NET generation . Neutrophil Macrophages - Secrete proinflammatory cytokines, antimicrobial TNF-α peptides, and degradative enzymes IL-6 IL-1β Granule - Phagocytose pathogens release - Present antigen Macrophage . Dendritic cells Complement - Phagocytose pathogens - Present antigen - Secrete cytokines such as IL- Phagocytosis 12, IL-15, IL-23
Abbreviation: NET, neutrophil extracellular trap. References: 1. Murphy K, ed. Janeway’s Immunobiology. 2012. 2. Kolaczkoska E, Kubes P. Nat Rev Immunol. 2013:13(3):159-175. Pattern Recognition Molecule (PRMs)
• Toll-like Receptors (TLRs) TOLL 1996 • NOD-like Receptors (NLRs) inflammation, apoptosis • RIG-I-like Receptors (RLRs)
• Pentraxins opsonization, complement cascade • Collectins • Ficollins
• C-type lectins phagocytosis • Scavenger receptors History of TLRs
• Christiane Nusslein-Vollhard 1985/1995* • Janeway linked TLR to NFkB 1997 • Jules Hoffman immune defense connection 95/2011 • Bruce Beutler Role of the LPS receptor 2011 Capsule Cytoplasm Cell Wall Ribosomes Few species have an DNA Mesosome adaptiive immune system (nucleoid) Plasma Membrane
Adaptive Immunity
innate immunity Key properties of the adaptive immune
Diverse repertoire of clonally distributed antigen receptors
Assembled by combinatorial assembly from an immense number of germline genes
Antigens can induce clonal selection to address a specific threat
Memory of a past exposure is banked away for more rapid responses
Memory at a cellular level is not passed to the next generation
Bad self-reactive memory can drive an autoimmune disease
Basic B cell biology
Somatic recombination generates functional Ig heavy and light chain genes
Antigen receptor genes move during B- and T-cell differentiation
Acquired tolerance necessitates alternative fates driven by the same antigen receptor
Two signal hypothesis (Bretscher and Cohn) Science 1970 169(3950):1042-9.
1
Signal 1 only = death/inactivation
1
Signal 1+ Signal 2 = activation 2
Courtesy of M. Cancro, U Penn Acquired tolerance necessitates alternative fates driven by the same antigen receptor
Two signal hypothesis (Bretscher and Cohn) Science 1970 169(3950):1042-9.
1
Signal 1 only = death/inactivation
1
Signal 1+ Signal 2 = activation 2
Signal 3 – molds the immune bias of the lymphocyte Courtesy of M. Cancro, U Penn B-cell development: Three types of Mature B cells
B1 lineage Central and Natural antibodies peripheral (defense from infection, tolerance Inflammation and autoimmunity) Short-lived HSC plasma cell Self Short-lived Bone marrow renewal or foetal liver Mature plasma cell B1 cell Extrafollicular Antigen response Peripheral Central tolerance GC reaction GC tolerance (after T-cell reaction) B cell Mature T cell Activated B cell HSC B2 cell
Bone Immature T1 T2 Memory marrow B cell B cell B cell B cell
Short-lived MZ B cell plasma cell Plasma Long-lived cell plasma cell HSC = haemopoietic stem cell; GC = germinal centre MZ = marginal zone Adapted from Dörner T, et al. Nature Rev Rheumatol 2009;5:433–41 Antigen-specific clonal selection
Humans have ~ 1011 B cells and 1011 T cells
distributed into ~ 106 B-cell and T-cell clones
Optimal T-dependent responses require coordination (physical interactions) of complementary B and T cell clones
For optimal kinetics of responses, this cannot come from random encounters
Spatiotemporal organization of B-T cell interactions
Frequencies of antigen-specific B cells and complementary and antigen-specific T cells are generally low
How do the B and T cells find each other in the body?
Each should provide what the other needs. INNATE Germinal centers: Arenas for -cell clonal selection
Properties of T Follicular Helper (TFH) cells
IL-21- pleotropic cytokine activates most lymphocytes
induces proliferation of CD40L activated B cells induces Activation Induced Deaminase (AID) for somatic hypermutation
With downregulation of T cell zone homing CC receptor 7 (CCR7) and IL-7 receptor-a (IL-7Ra)
TFH differentiation also affected by CD40L, CD26, STAT3, SLAM associated protein that all induce Bcl6.
Induce B cell differentiation at B-T border into extrafollicular plasmablasts
From Tangye et al. Nat Rev Immunol 2013 Germinal center reactions provide benefits for the mammalian adaptive immune system
• 1. Specialized anatomic site for coordinated spatiotemporal interactions of antigen-specific B cells and T cells.
• 2. Antigen-specific T cells (TFH) are required for second signals (soluble and membrane) inducing: - hypermutation machinery (e.g., AID) - survival (e.g., BAFF/BLyS) - differentiation (to plasma cell) - class-switch recombination (CSR).
• 3. Follicular dendritic cells help to provide a well furnished arena for competition between clonal daughters based on stregth of BDR signal and availability of second signals
Ag specific B cells and cognate peptide-antigen specific T cells: The perfect couple!
As each may represent < 1:10,0000 Lymphocyte clones, How do they find each other?
Don’t forget ICOS/ICOS-L and modulating inhibitory paired R-L systems BLyS/BAFF play fundamental roles in ensuring the survival of B cells • Potentially expressed by multiple immune cells1,2 –Neutrophils –Monocytes –Dendritic Cells –activated T cells –Plasma cells –B cells • BLyS (TNFSF13B) exists membrane-bound and soluble forms1 • Related to A Proiferation Inducing Ligand (APRIL,TNFSF13) • Three molecules bind together to form the trimeric soluble protein1,3 • BLyS is important in ensuring that new B cells mature, survive and differentiate1,3 1. Cancro MP, et al. J Clin Invest 2009;119:1066–73 2. Chu T, et al. Arthritis Rheum 2009;60:2083–93 3. Miller JP, et al. J Immunol 2006;176:6405–10 Mechanisms of B-cell tolerance for self-antigens in health – many steps that can be dysregulated causing autoimmune responses
Peripheral lymphoid organs GC Short-lived T Extrafollicular Fas-mediated response T PC T B lymphoblast apoptosis T B
T Absence of T Memory T T T-cell help Follicular T naïve Autoantigen-mediated T T apoptosis Anergy Somatic Absence of hypermutation Long-lived PC T-cell help • Increase avidity for foreign antigen • Eliminate autoreactivity Competitive disadvantage • Create autoreactivity de novo for survival factors (BAFF)
Courtesy of Jen Anolik U of Rochester Human Autoimmune Diseases associated with aberrant TFH cells
From Tangye et al. Nat Rev Immunol 2013 Ectopic Lymphoid Structures: Powerhouse of Autoimmunity
Corsiero Pitzalis 2016 Front Immunol. 2016 7:430. Long lived plasma cells provide persistent high level Ab defenses
Current Opin Immunol 20(2) 2008, Pages 162–169
Plasma cells are antibody producing factories
Lots of endoplasmic reticulum (ER) !
Autoimmune Disease: Seropositive Rheumatoid Arthritis is an archetype Autoimmunity and Pathogenetic B-cell mechanisms
Mature Bone Marrow Activation Blast Immature
T1 T2 Plasma cell Pro B Pre B
Spleen
FO MZ Plasmablast Memory GC B B T DC B IL- TNF-α LT FDC 6 DC T T Mφ ?
Lymphoid Antigen presentation Inflammatory Auto- Immune cytokines organogenesis and costimulation antibodies complexes ’ Multiple sclerosis Multiple sclerosis All autoimmune Graves disease SLE Sjögren’s syndrome SLE disorders Myasthenia gravis RA RA RA Pemphigus vulgaris SLE RA
Abbreviations: DC, dendritic cell; FDC, follicular dendritic cell; FO, follicular; GC, germinal center; Adapted from Martin Annu Rev Immunol 2006;24:467-96. IL, interleukin; LT, lymphotoxin; Mφ, macrophage; MZ, marginal zone; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus; TNF, tumor necrosis factor. HLA and Non-HLA Genes Are Linked in APCA-Positive Genome-Wide Association Studies (GWAS)* Value P
10 Log
Chromosome The grey horizontal line indicates SNPs that are significant at a genomewide level *SNPs plotted according to chromosomal location, with the log10 P values corrected with the use of genomic control. SNPs, single nucleotide polymorphism; MHC, major histocompatibility complex; TRAF1, TNF signal transduction gene; C5, complement 5 gene.
Plenge RM et al. N Engl J Med. 2007;357(12):1199-1209. 39 Antigen Presentation -- First Step in the development of Rheumatoid arthritis
-- Genetic Susceptibility- Certain Class II MHC alleles ie HLA-DR4 (DRB1) (*0401,*0404)
-- Antigen Presentation to T Lymphocyte (CD4+) Citrullination by Peptidylarginine Deiminase in Rheumatoid Arthritis
Annals of the New York Academy of Sciences Vol 1108, Issue 1, pp 323-339, 29 AUG 2007 DOI: 10.1196/annals.1422.034 41 Development of ACPA Repertoire Prior to Clinical Onset ACPA spreading occurs years before disease
Number of peptides recognized Reactivity to different peptides
The number of citrullinated peptides The reactivity to different citrullinated recognized increased over time peptides increased over time
van der Woude42 D et al. Ann Rheum Dis. 2010;69(8):1554-1561. Abstract 1091. RHEUMATOID ARTHRITIS: HYPOTHESIS FOR STAGES OF DISEASE
Epitope Spreading + Titer Elevation ACPA
RF Genetics
Cytokines - HLA-DRB1 (shared epitope)* - GWAS (PTPN22, others)
Healthy Autoimmune Early Synovitis OVERT Rheumatoid Arthritis Pre-Clinical - Arthritis - Smoking - Radiographic Changes - Hormones Phase - Remicade * - Bacteria* - Diet ? Environmental Treatment Factors Often merited
Klareskog and others Theoretical Pathway for Breaking Tolerance in RA Anti-CCP B cells More Autoreactive capture any T Cells citrullinated Autoreactive RF B cell protein, giving T Cells IgG anti-citrulline rise to expanded immune complexes T-cell responses against self- are antigens for RF antigens B cells
T Cell Anti-citrulline Plasma cell RF and anti-CCP antibodies lead to immune complexes, macrophage secretion Anti-citrulline of proinflammatory cytokines B Cell PADI
Citrullinated antigens Arginine-containing antigens Adapted from: Niewold TB, et al. QJM. 2007;100(4):193-201. 44
Citrullination, ACPA Formation, and IL-8 Expression Are Key Processes in Osteoclastogenesis in RA
Catrina AI, et al. Nat Rev Rheumatol. 2017;13:79-86. Osteoclastogenesis May Occur Before Clinical Disease Onset
Schett G, Gravallese E. Nat Rev Rheumatol. 2012;8:656-664. Bone Volume and Density Are Reduced in ACPA+ But Non-Arthritic Individuals
Arrows show cortical thinning, cortical fenestration as well as small bone erosions. ACPA, anti-citrullinated protein antibody. Kleyer A, et al. Ann Rheum Dis. 2014;73:854–60. 47 B cells and antibodies produced in rheumatoid asynovium drive pathogenesis
48 Catrina I I, et al. Nature Reviews in Rheum 10, 645 (2014) Diverse Recirculating Cells (Including Memory B Cells) Traffic Through Rheumatoid Joints
macrophage
T Cell TFN-a TFN-a T Cell TFN-a TFN-a B Cell TFN-a BAFF APRIL
Immature BAFF
B Cell Synoviocytes Neutrophil BAFF Dendritic cell BAFF
B Cell
Silverman GJ. Arthritis Rheum. 2006;54:2356-2367. Bad B cells in RA ACPA and RF are used as serological markers and aid diagnosis.
Serum ACPA and RF + patients have worse prognosis
Where are bad autoantibodies ACPA & RF made?
1. In affected synovium (ectopic lymphoid tissue), tht should respond to treatment
2. From long-lived plasma cells in the bone marrow?
3. Continuously produced by short-lived plasmablasts in peripheral lymphoid tissue (and affected joints)
Functional B cell abnormalities in RA: ACPA levels are proportional to levels of recirculating Bad ACPA memory
Where are serum ACPA made?
Bone Marrow Plasma cells?
Synovial Plasmablasts
Relationship to recirculating ACPA bearing B cells?
Pelzek et a. … Silverman Arth Rheum 2017 Clinical treatment to reduce inflammation (DAS remission) does not eradicate bad ACPA memory
Pelzek et a. … Silverman Arth Rheum 2017 Concluding remarks
In the adaptive immune system, Germinal center (GC) responses facilitate highly coordinated B-T cell interactions
With breach of immune tolerance to self antigens, GC responses may drive pathogenic immune responses
There are several stages at which immune dysregulation can contribute to autoimmune disease
Understanding B-T cell interactions has highlighted new therapeutic targets that include: Antigen-specific B cells and T cells Chemokine receptors/ligands Factors that regulate TFH cells B cell survival factors Factors that support long-lived plasma cells and others www.medlearning.com