Presentation on theme: "INNATE IMMUNITY: ANTIVIRAL STATE, KILLER CELLS, THE COMPLEMENT SYSTEM"— Presentation transcript:
1 INNATE IMMUNITY: ANTIVIRAL STATE, KILLER CELLS, THE COMPLEMENT SYSTEM 3RD SEMINARINNATE IMMUNITY: ANTIVIRAL STATE, KILLER CELLS, THE COMPLEMENT SYSTEM
2 DANGER SIGNALS ARE TRANSLATED TO CYTOKINE SECRETION THROUGH VARIOUS MOLECULAR SENSORS IN DC SUBTYPES 46621151037978RLRNLRRLRPlasmacytoid DCConventional DCIL-1βIL-12/23IL-10TLR1 – bacterial lipoprotein (together with TLR2)TLR2 – bacterial lipoprotein, peptidoglycane, lipoteicholic acid(heteromer with TLR1 and TLR6)TLR3 – viral dsRNATLR4 – bacterial LPSTLR5 – bacterial flagellinTLR6 – bacterial lipoprotein (together with TLR2)TLR7 – viral ssRNATLR8 – viral ssRNATLR9 – unmethylated CpG DNATLR10 – modified viral nucleotidesNLRs – microbial products, DAMPsRLRs – viral dsRNAIFNα IFNβ
3 THE TYPE I INTERFERON RESPONSE: ANTIVIRAL STATE plasmacytoid dendritic cellsPlasmacytoid dendritic cells (pDCs) produce 1000x more type I interferon than other cells (Natural Interferon Producing Cells – NIPC)After viral infection they are accumulated at the T cell zone of the lymph nodes
4 VIRUS-INDUCED TYPE I INTERFERON PRODUCTION paracrineautocrineInfected cellsubtypesIFN-IFN-IFN responseIRF-3IRF-7VirusNFBAP-1Type I IFN receptorIRF: interferon regulatory factor
5 INTERFERON EFFECTOR PATHWAYS induction of the „antiviral state” 1. Mx GTPase pathwayblock viral transcription2. 2',5'-oligoadenylate-synthetase (OAS)-directed Ribonuclease L pathwaydegrade viral RNA3. Protein kinase R (PKR) pathway (Ser/Thr kinase, dsRNA- dependent)inhibit translation4. ISG15 ubiquitin-like pathwaymodify protein functionCONTROL ALL STEPS OF VIRAL REPLICATION
6 MULTIPLE EFFECTS OF TYPE I INTERFERONS TRIFTANKIKKεTBK1IRF-3TRAMTLR3TLR4MyD88IRF-5TLR7TLR8TLR9IFN-β, IFN-αRIG-1Stimulation of Ig-productionin B-cellsType I interferon receptorIRF-7Increased citotoxicity and proliferation of NK-cellsActivation of - and γδ T-cellsIncreased antigen presentationin myeloid dendritic cellsIRAK-1TRAF-6
7 EFFECTOR MECHANISMS OF INNATE IMMUNITY KILLER CELLSCOMPLEMENT SYSTEMPHAGOCYTIC CELLS
8 NK CELLS Similar functions to cytotoxic T cells but: larger than lymphocytesno rearranged antigen-specific receptorscontain large cytoplasmic granulesrespond fast, circulate in a partly activated state
9 RECOGNITION AND KILLING BY NK CELLS KIRKARContents of lytic granules:Perforin: forming pores in the target cell membrane lysisGranzyme: inducing apoptosis in the target cell
10 NATURAL KILLER CELL ACTIVATION NK-CELLSVirus-infectedcellPRRRECOGNITIONACTIVATIONLysis of infected cellRECOGNITION OF ALTERED HOST CELLSKinetics of the activity of the complement system and NK cells in virus infectionIFNIL-12Complement systemNK-cellsdaysRelative level/activity
11 EFFECTOR MECHANISMS OF INNATE IMMUNITY KILLER CELLSCOMPLEMENT SYSTEMPHAGOCYTIC CELLS
12 THE COMPLEMENT SYSTEMThe complement system is a set of plasma proteins that act in a cascade to attack and kill extracellular pathogens.Approximately 30 components:activating moleculesregulator factorscomplement receptorsmembrane proteins which inhibit the lysis of host cellsMost of the complement proteins and glycoproteins are produced in the liver in an inactive form (zymogen). Activation is induced by proteolytic cleavage.
13 AMPLIFICATION OF THE COMPLEMENT CASCADE limitedproteolysisinactive precursorsenzymeactivating surfaceActivating surface needed!
14 ACTIVATION OF THE COMPLEMENT SYSTEM Clearence of Immune complexes
16 THE C1 COMPLEXCollagen „legs”Gobular „heads”C1 is always present in serum but it requires an activating surface for activationLow affinity binding to the Fc region of antibody conformational change activation
18 THE CLASSICAL PATHWAY: FIXATION OF COMPLEMENT, GENERATION OF C3b BY THE CLASSICAL C3 CONVERTASE When soluble pentameric IgM in the 'planar' conformation establishes multipoint binding to antigens on a pathogen surface, it adopts the 'staple' conformation and exposes its binding sites for the C1q component of C1. Activated C1 then cleaves C2 and C4, and the C2a and C4b fragments form the classical C3 convertase on the pathogen surface. Conversion of C3 to C3b leads to the attachment of C3b to the pathogen surface and the recruitment of effector functions (i.e. opsonisation). C3a recruits phagocytic cells to the site of infection.
20 GLYCOSYLATION OF PROTEINS IS DIFFERENT IN VARIOUS SPECIES Eukariotic cellsProkariotic cellsgalactoseglucoseaminemannose (polymer = mannan)neuraminic acid(sialic acid)
21 MANNOSE-BINDING LECTIN (MBL) PATHWAY MBL: part of the collectin familysimilar structure to C1 complex, MASP-1,2 ~ C1r,sbinds mannose and similar sugar molecules on the surface of bacteria, fungi, protozoa and viruses conformational change cleavage of C2 and C4 moleculesMASP = MBL-associated serin protease
22 ACTIVATION OF THE MBL COMPLEX The literature sometimes refers to the bigger fragment of C2 as C2a but it is more consequent if we use ‚b’ for the bigger fragments of all complement molecules
24 C3b can derive from classical or the lectin pathway too Alternative pathway is instantly inactivated on eukaryotic cell surfaces (in the presence of sialic acid molecules)In the plasma close to a microbial surface the thioester bond of C3 spontaneously hydrolyzes at low frequency. This activates the C3, which then binds factor B. Cleavage of B by the serine protease factor D produces a soluble C3 convertase, called iC3Bb, which then activates C3 molecules by cleavage into C3b and C3a. In this complex the Bb fragment of factor B provides the protease activity to cleave C3, and the C3b fragment of C3 locates the enzyme to the pathogen's surface.
25 THE CENTRAL COMPONENT OF THE COMPLEMENT SYSTEM C3 proteis have one of the highest levels in the serum: 1.2 mg / mlStrong covalent binding Complement fixation( molecules/ml)
26 C3 convertase + C3b = C5 convertase (C4bC2bC3b)Figure 2.12 Complement component C5 is cleaved by C5 convertase to give a soluble active C5b fragment.The C5 convertase of the alternative pathway consists of two molecules of C3b and one of Bb (C3b2Bb). C5 binds to the C3b component of the convertase and is cleaved into fragments C5a and C5b, of which C5b initiates the assembly of the terminal complement components to form the membrane-attack complex.The classical and alternative C3 convertase is different in structure but common in function
27 MEMBRANE ATTACK COMPLEX (MAC = C5b-C9n) MACs in the cell membranePore formation osmotic lysis of pathogens
34 DEFICIENCIES OF COMPLEMENT COMPONENTS AND REGULATORS Deficient complement proteinEffects of deficiencyC1, C2, C4 C3Immune-complex diseases (similar to SLE), susceptibility to pyogenic infectionsMAC, alternative pathway componentsSusceptibility to Neisserial infectionsC1INHHereditary angioneurotic edema (HANE)DAF (CD55), MIRL (CD59)Paroxysmal nocturnal hemoglobinuria (PNH)
35 HEREDITARY ANGIONEUROTIC EDEMA (HANE) (HEREDITARY C1INH DEFECT) Inhibition by C1INH in many stepsbradykinin and C2-kinin: enhance the permeability of postcapillar venules edemaC1 is always active without activating surface because plasmin is always activeMain symptoms:swellings of skin, guts, respiratory tractsserious acute abdominal pain, vomitinglarynx swelling – suffocation, may cause deathTreatment:iv C1INH, FFP, steroidkallikrein and bradykinin receptor antagonistsFFP= Fresh Frozen PlasmaChildren with symptoms of HANE
36 PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) Acquired clonal mutation of PIG-A gene in myeloid progenitors – no GPI-enchored proteins in the cell membrane of affected cells (rbc, plt, wbc)CD59 and CD55 complement regulatory proteins are GPI-enchored proteinsNo CD59 and/or CD55 PNH patients are highly susceptible to complement-mediated lysisThe lysis of red blood cells leads to high levels of hemoglobins in the blood that appears in the urine (hemoglobinuria)Elevated levels of TF derived from complement-damaged leukocytes cause thrombosesPIG-A = Phosphatidylinositol N-acetylglucosaminyltransferase subunit AGPI= glycosylphosphatidylinositolParoxysmal = sudden attacksNocturnal = occuring at night
37 Change in the colour of urine samples taken from PNH patient during the day Only minority of patients have this symptom.
38 PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) SYMPTOMSTHERAPYHaemolytic anaemia andassociated symptomsHaemoglobin and its products in the urineThrombosis:brain veins,mesentheric veins,hepatic veins (Budd-Chiari-syndrome)May transform to leukemia or other bone marrow diseasesSpecific th.: eculizumab (Soliris) = anti-C5 monoclonal antibodyCurative th.: bone marrow transplantationAlternative th.: steroids (general immunosuppression)Anticoagulants: s.c. heparin p.o. kumarinIron replacementTransfusion (filtered-irradiated blood)