Non-Specific Immunity Innate (natural, native, non-specific) immunity • Always present, ready to recognise and eliminate microbes. May be stimulat also by non-microbial agents. • Frequently eliminates microbes before the specific immunity becomes active. • Receptors are encoded in the germline, are not a product of recombination of genes. Differences between the Innate and Acquired Immunity • Innate Immunity – Universal – Rapid – Lacks memory • Acquired Immunity – Not universal – ‘Slow’ to develop – Memory – Specific but in some situations reacts to autoantigens – ‘Plays to the tune of the innate immune system’ Signals of danger - EXOGENEOUS (PAMPs) -ENDOGENEOU (e.g. STRESS PROTEINS RELEASD FROM NECROTIC CELL) Inborn immunity – activating signals (alarmins) Pathogen-Associated Molecular Patterns (PAMPs) (C. A. Jeneway,Jr, 1989) microbial structures, motifs, present in large groups of microorganisms, necessary for their life e.g. lipopolysachrides, lipopeptides, peptidoglycans, manose nonmetylated CpG present in bacterial DNA, dsRNA of RNA-vises Danger, Damage-Associated Molecular atterns (DAMPs) (Polly Celine Eveline Matzinger,1994) Molecular structures of the host macroorganism e.g. HSP60, HSP70, fragments of fibrinogen, fibronectin, hyaluronan.. Downloaded from: StudentConsult (on 19 July 2006 06:34 AM) © 2005 Elsevier Differences between innate and specific immunity PAMPs – pathogen-associated molecular patterns exogenou substances activating non-specific immunity (Endotoxin, mannose, double-stranded RNA, unmelylated CpG nucleotides) DAMPs – danger associated molecular patterns – endogenous substances stimulating non specific immunity – heat shock proteins, uric acid PRR- Pattern recognition receptors - recognize PAMPs, DAMPs. TOLL-like receptors –surface or intracellular receptors recognizing various PAMPs. Expressed on dendritic cells, macrophages, granulocytes, epitelial cells…. They induce activation of these cells. TOLL-LIKE RECEPTORS Downloaded from: StudentConsult (on 19 July 2006 06:34 AM) © 2005 Elsevier Activation by Toll-like Receptors and by Cytokine Receptors Basic components of non-specific defence • Non Specific barriers – Anatomical/Physiological • Acute phase reactants and Inflammation – Complement/Interferons/CRP • Innate cells – PMN/Macrophages/NK cells Non-specific barriers of human body The Complement System General features of the Complement System Activation • Inactive, preformed protein is activated by the proteolytic cleavage. • It is cleft into the smaller part (called a) and a bigger part (called b). • Usually the bigger part has also proteolytic activity, while the smaller part has various other biological activities (chemotactic, anaphylatoxic). • Component C6-C9 are activated without cleavage, they just „attach“ to the complex of the other complement components. Activation of the complement sytsem anaphylatoxin inflammation, phagocyte recruitment C4a, C3a, C5a lytic pathway formation of membrane-attack comlex, lysis of pathogens C5b, C6, C7, C8, C9 opsonization phagocytosis C3b Alternative pathway spontaneous activation C3 C3b Bf Factor D Bb Lectin pathway mannose binding MBL MASP-1 MASP-2 C4/C2 C4b/C2b Classical pathway antibody binding C1q/r2/s2 C4/C2 C4b/C2b C3 convertase C3 C3a + C3b C3b/Bb C4b/C2b C4b/C2b C5 convertase C5 C5b Complement system Complement system activation • Classical pathway: – Complexes IgG-antigen, IgM-antigen, – C-reactive protein • Alternative pathwas – Lipopolysaccharide of G- bacteria – Cell wall of some bacteria – Cell wall of the yeasts (zymozan) – Aggregated IgA • Lectin pathway: – Mannose and other sacharides Downloaded from: StudentConsult (on 19 July 2006 06:34 AM) © 2005 Elsevier The Complement System C1 C2 C4 C2aC4b C3 C3a C3b C5 C5a C5b C5b, C6, C7, C8 IgG C9 Classical pathway complement activation Effect of C9 Actiation of Alternative Pathway of the Complement system C3 C3 C3aC3a B Ba Activating surfaces + proteolysis D, P C3b C3 Convertase C5 Convertase C3b, Bb, C3bC3b, Bb Regulation of the Complement System • Factors present in plasma – Classical pathway – mainly C1-inhibitor - C1-INH (deficiency leads to hereditary angioedema). – Alternative pathway – factor H, factor I • Faktors on cell membranes: – CD59, CD55 (DAF - decay accelerating factor) - CD46 Patothogenetic Significance of the Complement System • Deficit of components of the classical and alternative pathways – proneness to bacterial infections and to systemic autoimmune diseases. • C1-INH deficiency: hereditary angioedema. • Mutations of factor H – atypical hemolytic-uremic syndrome. • Several polymorphisms of factor H are linked to senile macullar degeneration. • Paroxysmal night hemoglobinuria – caused by mutations of the gene PIG-A (product if this gene binds CD 55 and CD 59 into cytoplasmatic membrane. Biological effects of activated complement system • C9 - cytolytic effect • C3b - opsonisation • C3a, C5a – anaphylatoxins, liberation of histamine • C5a - chemotaxin Phagocytosis Phagocytic cells • Polymorphonuclear granulocytes • Monocytes + macrophages • Dendritic cells mainly non-activated cells. After activation they loose most of their phagocytic activity. Downloaded from: StudentConsult (on 19 July 2006 06:34 AM) © 2005 Elsevier Polymorphonuclear granulocyte Normal blood count (in adults) • Erythrocytes: 4-5 x 1012/l • Thrombocytes: 150-300 x 109/l • Leukocytes: 4-9 x 109/l – Granulocytes: 55-70% – Eosinophils: 1-4% – Basophils: 0-1% – Lymphocytes: 24-40% – Monocytes: 3-8% Macrophages • Derived from blood monocytes. • Connective tissue macrophages – Kupffer cells (liver) – Alveolar macrophages (lungs) – Microglia (CNS) – Osteoclasts (bone) – Peritoneal macrophages Downloaded from: StudentConsult (on 19 July 2006 06:34 AM) © 2005 Elsevier Development of macrophages Downloaded from: StudentConsult (on 19 July 2006 06:34 AM) © 2005 Elsevier Extravasation of leukocytes Chemotaxins • Attract phagocytic cells • Products of destroyed cells • C5a • IL-7, IL-1 • Leukotriens Opsonins • Substances enhancing phagocytic process by improving attachment of the particle to the phagocytic cell. • Specific: IgG, (IgM only indirectly by activation of the complement system) • Non- specific: C3b, fibronectin…. Downloaded from: StudentConsult (on 19 July 2006 06:34 AM) © 2005 Elsevier Steps of phagocytosis Killing mechanisms of phagocytic cells • Reactive metabolites of oxygen (H2O2, hydroxyl radical (.OH), superoxide aniont (O2 -), singletted oxygen (.O2) • Reactive nitrogem intermediates (NO, NO2) • Hydrolases: protease, lipases, DNAses • Low pH • Lysozyme • Lactoferin • Defensins – antimicrobial polypeptides Lysozyme • Cleaves cell walls of G+ bacteria • Present in granules of neutrophil granulocytes, in plasma, secretions. Defensins • Polypeptides with antibiotic-like effect against bacteria and fungi. • Produced mainly by granulocytes and by epithelial cells. • Lead to desintegration of cell membranes, formation of pores in membranes . • Main groups are a and b defensins Natural killers (NK cells) • Originate in non-T non-B lymphocyte lineage. • Morphologically: large granulated lymphocytes (LGL). • Recognition of target cells in antigen non-specific. • Virus infected and tumor cells are killed. • Target cells are recognised mainly by decreased HLA-I expression. • Cytotoxic mechanisms are similar to Tc cells: perforin and induction of apoptosis. • Produce various cytokines, e.g. IFN-g, IL-12 Large granulated lymphocyte Antibody dependent cellular cytotoxicity (ADCC) Fc receptor Virus-infected Cell NK Cell perforin granzyne IgG Fab Fc Epitope Interferons (IFN) • Type 1: IFN a, IFN b – produced mainly by virus-infected cells (fibroblasts, granulocytes. Lead to inhibition of the virus replication in target cells. • Type 2 - „Immune interferon“: IFN g: is produced by activated TH1+ cells, NK cells . Induces activation of macrophages. • Interferon type 3 - IFN l - IL28A,B, IL-29 – similar to IFN-I The action of interferon (IFN) Virus Viral nucleic acid New viruses Antiviral proteins block viral reproduction Interferon molecules produced Interferon binding simulates cell to turn on genes for antiviral proteins Host cell 1 • Infected by virus • Makes interferon • Is kiled by virus Host cell 2 • Entered by interferon from cell 1; • Interferon induces changes that protect it Inflammation • A rapid response to wounding and infection • An important consequence of innate immunity • Cardinal features – rubor (redness), calor (heat), tumor (swelling), dolor (pain) • Local consequences of inflammation – Increased blood flow to affected area – Recruitment of phagocytes to affected area, particularly neutrophils and macrophages – Alteration of vascular permeability leading to entry of soluble molecules from the plasma Local mediators of inflammation • Products of activation of the kinin, complement, and coagulation systems. Usually C3a and C5a plays a significant role. • Vasoactive amines – histamin, serotonin - reased from the damaged cells or stimulated macrophages. • Metabolites of arachidonic acid • Platelet activating factor • Produkty of monocytes and granulocytes: IL-1, TNF-a, IL-6, IL-18, chemokines, NO, • Produkts of activated lymphocytes: TNF-a, IL-6, IFN-g, chemokines General symptoms and signs of inflammation • Orchestrated mainly by IL-1, IL-6, TNF-a • Fever • Fatigue, somnolence • Loss of appetite • Laboratory signs: leukocytosis, increased ESR, increase in accute phase proteins, decreased levels of iron and zinc in serum. Accute-phase proteins • Serum levels are increased during inflammation • Produced by the liver after stimulation by IL-1, IL-6, TNF-a • Best known: C-reactive protein • Others: Complement components, A1-AT, fibronectin.. Accute phase response Initiation of inflammatory response Skin Bacteria 1. 2. 3. Skin Pin Blood clot Red blood cells Phagocyte Step 1 Damaged tissues increasing blood flow to the area Step 2 Histamines cause capillaries to leak, releasing phagocytes and clotting factors into the wound Step 3 Phagocytes engulf bacteria, dead cells, and cellular debris C3a C5a Drugs modulating inflammatory process • Glucocorticoids • Non-steroidal anti-rheumatic (anti-phlogistic) drugs (acidosalicylic acid, paracetamole,…) • Antimalarics • Gold • Monoclonal antibodies against inflammatory cytokines and adhesion molecules