Immunology PDF

CLINICAL IMMUNOLOGY Mihai Bojincă  Immunity / immune response Immunity = the totality of mechanisms used by the body to recognize and neutralize foreign and / or agressive structures. Immune response = the response induced by the entrance of an antigen in the body.  The immune...

CLINICAL IMMUNOLOGY Mihai Bojincă  Immunity / immune response Immunity = the totality of mechanisms used by the body to recognize and neutralize foreign and / or agressive structures. Immune response = the response induced by the entrance of an antigen in the body.  The immune system A series of cells and soluble factors that collaborate to protect the host from pathogens. Designed to differentiate normal molecular structures (proteins, lipids, sugars, nucleic acids) of the host from structures that are damaged or components of pathogens. The differentiation between self and non-self is accomplished by both innate and adaptive mechanisms.  The innate immune system (IIS) CARACTERISTICS: Present from birth, genetically determined First barrier against aggressions Activated immediately (20-30 min after exposure to pathogen) Rapidly controls the replication of the infecting pathogen Nonspecific action Identical behavior in the case of reexposion No immunologic memory  Components of the innate immunity – Mechanical barriers (skin, mucosa, tears, saliva, acid pH, temp. O2) – Humoral factors (complement, acute phase reactants, cytokines) – Phagocytic cells of myelomonocytic lineage, neutrophils – Lymphocytes of innate immunity (NK, ILC)  Activation of IIS PRR (pattern- recognition receptors) ex. TLR (Toll-like receptors) PRR recognize and interact with motifs specific to microbes, viruses and damaged tissues PAMPs (pathogen-associated molecular patterns) bacterial LPZ, mannans, flagellin, viral DNA/RNA DAMPs (damage-associated molecular patterns) including alarmins - endogenous molecules constitutively available and passively released from necrotic cells: HMGB1, HSP 60, 70, antimicrobial peptides: β-defensins, cathelicidin Inflammasome activation  Neutrophils First cells recruited to sites of inflammation by a variety of chemotactic signals They neutralize the invading microbes by at least 2 mechanisms: – Phagocytose of the invading microbe the phagosome (microbe and intracellular granules with peptides, proteases, highly reactive oxidizing agents) – Neutrophil extracellular traps (NETs) – upon activation neutrophils release granules, proteins and histones that are bound to a mesh – like structure formed by DNA and histones and that kill microbes independent of phagocytic uptake.  NETosis Amulic B, Hayes G. Current Biology Vol 21 No 9 R298. C. M. de Bont et al.Cellular & Molecular Immunology 2018  The mononuclear-phagocytic system – Identical medular lineage – Same morphology (mononuclear cells) – Same function (phagocytosis) MONOCYTES 1-8% of WBC, ø 10-15μ, T½ 8-12 h MACROPHAGES (Mf) ø10-25 μ, lyzozomal granules Activation ⇔ cytokines (IFN-γ), Ag, mitogens. ⇒ Mf = APC (antigen presenting cell) and effector cell  Macrophage Surphace receptors – Immune: for Fc of IgG (FcγR I, II, III), IgE (FcεR) for C (CR1, CR3, CR4) Adhesion mollecules – Nonimmune: for glycoproteins from bacterial surface for denaturated proteines for fibronectin for tumoral antigens for hormones  Macrophage - secretion products - 1. Factors of cellular 6. Coagulation factors: differentiation: – Tisular thromboplastine, – CSF FV, VII, IX, X 2. Regulators of cellular function: 7. Plasmatic proteins: – IL-1, IL-8, TNF-α, IFN-γ, PDGF – α2-macroglobulin, α1-antitripsin, fibronectine 3. Hydrolitic enzymes: - Colagenase, lipase, elastase 8. O metabolites: – O3, H2O2, HO- 5. Complement components – C1-C5, B, D 10. NO 5. Arachidonic acid metabolites: – PGE2, LTC4, TxB2  Antigen presenting cells (APC) Capture, processing and presenting Ag to lymphocytes Release of activating cytokines Macrophages Dendritic cells (DC) B lymphocytes Other cells  Complement system - biologic functions - Inflammation – Activation of neutrophils, Mf – Chemotaxis – Degranulation of mast cells – Increasing vascular permeability – Smooth muscle contraction Cell lysis Viral neutralisation Opsonisation (coating the surface of a target such a bacteria) Clearance of immune complexes Activation of complement 1. Classical pathway TRIGGERED BY: – Ag-Ac (IgG1, IgG3, IgM) – Ag – Viruses – Endotoxines C5a, C3a ⇒ chemotaxis and mast cell activation – “anaphylatoxins”  Complement activation 2. Alternative pathway Triggered by: – Bacterial components – Ig (aggregated IgA, IgG4) – Polysaccharides – Enzymes  Complement activation 3. Lectin pathway MBL – mannan-binding lectine initiates the pathway and belongs to the same family as C1q MASP-1 (MBL-associated serine-protease-1) ~ C1r MASP-2 (MBL-associated serine-protease-2) ~ C1s MAC (membrane attack complex)  Cytokines Tumour necrosis factor (TNF) – pro inflammatory, activation of neutrophils, endothelial cells, fever, synthesis of acute phase proteins. Rheumatoid arthritis, ankylosing spondylitis (AS), Crohn disease Interleukin 1 (IL-1) – pro inflammatory, fever, endothelial cells activation, synthesis of acute phase proteins. Gout, Mediterranean fever Interleukin 6 (IL-6) – pro inflammatory, synthesis of acute phase proteins, fever, B cells activation. Rheumatoid arthritis, vasculitis Interleukin 17 (IL-17) – pro inflammatory. Psoriatic arthritis, ankylosing spondylitis  NK Lymphocytes Large granular lymphocytes, present from birth, derived from a lineage different from T and B cell – 5-10% of the circulating lymphocyte population. Characteristic surface molecules - CD16, CD56 Blood, spleen, a few in pulmonary interstitial area, bowel, liver Receptors for Fc IgG1 and IgG3 ⇒ ADCC (antibody dependent cell mediated cytotoxicity) Cytokines secretion NO MHC (Major Histocompatibility Complex) restriction NO antigenic specificity NO immunologic memory  NK Cells Cytotoxic for tumor cells / viral infected - ADCC (antibody dependent cell mediated cytotoxicity) ⇑ Mf capacity of phagocytosis NK Cells - ADCC  Adaptive immune system (AIS) - T and B lymphocytes (LT, LB) - Immunizing event Natural Passive (through placenta ) Active (convalescence) Artificial Passive (serotherapy – antitoxins) Active (vaccination)  Adaptive immunity CHARACTERISTICS: Specificity Diversity Memory Specialization Autolimitation Non-reactivity to self  Lymphoid system CENTRAL PERIPHERAL LYMPHOID ORGANS LYMPHOID ORGANS Capsulated organs Fetal liver Spleen and lymph nodes Bone marrow Diffuse lymphoid tissue GALT (gut associated lymphoid tissue) Thymus BALT (bronchial associated lymphoid tissue) SALT (skin associated lymphoid tissue) Bone marrow Lymphocytes differentiation Thymus  Spleen 2 parts – Red pulp with Mf for the phagocytosis of senescent erythrocytes – White pulp - (PALS - Periarteriolar Lymphoid Sheath) Periarteriolar area ⇒ T cells (thymodependent area) At the periferic zone of PALS ⇒ B cells (thymoindependent area) Lymph node  Lymph node B – dependent area (cortical): – LB - lymphoid follicles – Plasma cells (Pl) - germinative centers T dependent area (paracortical) - – LT Medullar area: blood and lymphatic vessels, LT, LB, Pl, Mf, dendritic cells.  Diffuse lymphoid tissue – GALT (gut associated lymphoid tissue) + Waldeyer lymphatic ring - palatine, pharynx and lingual tonsils, Peyer’s patches, appendix – BALT (bronchial associated lymphoid tissue) – SALT (skin associated lymphoid tissue) T cells 60-80% from total lymphocytes, Long life (months, years) Surface receptors: – TCR-CD3 – CD2 (LT, NK) – CD4 (LTh) – CD8 (LTc) – CD28 – LFA-1(CD11a)  B cells 5-10% of lymphocytes, Short life (days) Surface receptors: – for Ag (BCR) – for Fc (FcγRI, II, III) – for C (CD35 for C3b) – MHC I and II – CD5, CD19, CD20 – CD10 (CALLA) – CD21 (for Epstein-Barr virus) – LFA-1 – L-selectine  Antigen (“antibody generator”) Molecules able to induce an immune response and react with its products (activated T cells or antibodies (Ab) - Ig) Remember: – Immunogen – only immune response – Tolerogen – suppressor mecanisms – AutoAg/tumoral Ag – endogene Ag  Antigenic determinants - epitopes Linear Conformational Valency Paratope – the structure of the Ab that is able to combine with the epitope because it has a complementary conformation  Clasification of antigens Structural criteria – complete – incomplete (haptens) Chemical criteria – Proteins – Glycoproteins (blood types A,B, Rh antigens) – Small peptides (insulin, GH) – Polysaccharides – Nucleic acids – Lipids  Antigens Autologous Ag – from the same person Syngeneic – genetical identical – twins or clones Alloantigen – present in some members of a species Xenoantigen – from another species, intense immunogenic Heterophile antigens – common to different species Organ / tissue specific antigens Sequestred antigens MHC (Major Histocompatibility Complex) = HLA (Human Leukocyte Antigen) CR 6 MHC II III I DP DQ DR B C A HLA  MHC I On nucleated cells Endogen Ag Bind CD8 presentation IFNαand β Graft rejection Cellular immune response  MHC II On cells implicated in immune response Exogene Ag presentation Bind CD4 Cooperation with T cells IFNα, IL-4, Il-13, Minor role in graft TNFαand β rejection Ag processing Ag recognition  T cell activation Ag recognition by TCR – MHC IL-2 production - clonal expansion Immune activation IL-2, IL-4, IFN - γ, TNF - α synthesis Macrophage activation LT CD8 activation LB activation Antibody secretion Antibody secretion  Immunoglobulines (Ig) Glycoproteins Synthetised by activated B cells (plasmocytes) Associated with cell membranes or circulating Found in serum (20% plasmatic proteins), extra-vascular fluids, lymphoid tissue  Immunoglobulines Immunoglobulines (Ig) Ig monomer: – 2 heavy chains (H): - IgG (γ) - 5 types - IgA (α) - IgM(μ) - IgD (δ) - IgE (ε) – 2 light chains (L): - K = 2/3 -λ Only K or λ in one Ig. Ig structure (monomeric basic unit)  Immunoglobulin The variable domain (H + L) – aminoterminal fragment - Fab: recognize and binds the Ag The constant domain H carboxyterminal Fc: - differentiates Ig classes and subclasses (9) - binds and activates C3 - binds specific celullar receptors - It is used for transplacentary transportation of Ig  Ig G 70 – 90% total Ig – 4 subclasses γ: - IgG1 (70%) = cross the placenta. Complement activation (++) - IgG2 = Complement activation (+) - IgG3 = Complement activation (+++) - IgG4 (4%) = Complement activation = 0. Reaginic activity  Ig G Very effective in antimicrobial defence (IgG1) Activation of complement. Opsonisation Neutralisation of bacterial endotoxins Secondary immune response Small dimensions = they pass trough the endothelium and can diffuse in the extravascular space By crossing the placenta they offer immunity for the neonate (passive immunisation). Ig M Pentameric structure Primary immune response C1q activation  Ig A Major mucosal Ig – dimeric form Secretory component prevents digestion of Ig in the intestinal and bronchial secretions  Ig D, Ig E Ig D – 2 δ heavy chains, 2 light chains: λ/ K = 4 Ig D = mIg, BCR Ig E – no complement activation, no crossing the placenta Ig E attaches to the FcR of basophils and mast cells – antiparasitic effect, allergic reactions  Characteristics of Ig C H Opsoni-z C Gm T½ J chain activati chain ation on 1200 150 IgG mg/dl kDa 21 days γ 1,2,3,4 - +++ ++++ 160 200 IgA mg/dl (1000)k 6 days α + - + Da 120 900 IgM mg/dl kDa 5 days μ 1,2 + ++++ - 3-5 180 2-3 IgD mg/dl kDa days δ - - - 0.05 190 IgE mg/dl kDa 24-48 h ε - - -  Immunoglobulines Isotypes (classes) = antibodies with different heavy chains Ig G, A, M, D, E - differentiates species. Allotypes = individual specificity of Ig - posttransfusional reaction. Idiotypes = specific only for the Ig made by same clone.  Immune reactions - Gell and Coombs - Type I – immediate hypersensitivity Type II – antibodies dependent cytotoxicity Type III – immune complexes mediated disease Type IV – delayed hypersensitivity  Type I Atopic individuals. Ag = allergen Ab = IgE induced by Ag : - first contact →IgE on FcR of the basophils / mast cells - second contact → Ag + IgE - FcR → degranulation. Clinical manifestations: Asthma. Seasonal hayfever. Atopic dermatitis Anaphylactic shock  Type II - Antibody dependent cytotoxicity Ag - Structural component of cellular membrane. - Haptene (small incomplete Ag) atached to the cell membrane. Target cells: blood cells, endothelial cells, renal basement membranes Ab : IgM/IgG Ag + Ab = + complement activation → cell lysis, phagocytosis NK cells - ADCC  Type II Clinical aspects: incompatible blood transfusions, SLE, autoimmune haemolytic anemias, autoimmune trombocytopenia, myasthenia gravis. Type III Immune complexes can form in the circulation or at the local sites. Antigens (excess of Ag): – Exogens: bacteria, viruses – Endogens: nuclear Ag, renal tubular Ag Antibodies must activate C (IgG1,3, IgM) C3a, C4a, C5a ⇒ anaphylatoxins  Type III ⇑ blood vessel permeability, chemotactism for basophils, eosinophils and neutrophils Leucocytes - exocytose of lysosomal enzimes onto the site of deposition Platelets aggregates and continue to produce vasoactive amines ⇒ microthrombosis Serum sickness, vasculitis, glomerulonephritis, SLE, RA  Type IV LTh CD4+ Increased level of cytokines ( IFN-α, MAF, MCF, IL-2, TNF-β Mf activation - Inflammation - Cell damage Clinical aspects: 1. Contact dermatitis (nickel, chrome, rubber products) 2. Tuberculin hypersensitivity 3. Granulomatous hypersensitivity (zirconium, beryllium, talc, silica, sarcoidosis, leprosy, parasites, Crohns disease)  Immunity and inflammation Autoimmunity and autoinflammation De Jesus A, Goldbach-Mansky R. Annu Rev Med. 2014  Model of development of autoimmune rheumatic diseases Deane KD, El-Gabalawy H. Nat Rev Rheumatol 2014  Rheumatoid arthritis IL-1 Osteoclast Chondrocyte IL-6 Regulatory T cell IL-12 IL-15 IL-18 IL-23 IL-10 IL-1 IL-1 IFNα TGF-β IL-17 IL-17 TNFα IL-6 IFNβ IL-17 Synovial fibroblasts IL-1 IL-21 IL-6 IL-18 IL-7 IL-6 TH17 IL-22 TNFα TGFβ IL-23 TH 0 TGFβ IL-12 IL-2 IFN-γ IL-6 TNFα TNFα IFNγ IL-4 IL-15 Dendritic cell IL-6 TH1 IL-18 Macrophage IL-1 TNFα IL-6 IL-17 TH2 IL-18 IL-10 IL-6 B cell Plasma cell Autoantibody Mast cell Neutrophil synthesis 1. McInnes IB, Schett Gl. Nat Rev Immunol. 2007;7(6):429-442. 2. Smolen JS et al. Nat Rev Rheumatol. 2012;8(4):235-243. 3. 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