complement and complement deficiency

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complement and complement deficiency

  1. 1. Complement and complement deficiency<br />Boonthorn<br />4 September 2009<br />
  2. 2. Outline<br />Complement pathway activation<br />Classical pathway<br />Alternative pathway<br />Lectin activation pathway<br />Membrane attack complex<br />Complement receptors and biological functions<br />Regulation of complement activation<br />Disorders associated with complement deficiency<br />Management of complement deficiencies<br />
  3. 3. Complement system<br />Important part of innate immune system<br />Major effector mechanism of humoral immunity<br />Named by Jules Bordet ( 1919 , Nobel Prize )<br />Group of serum protein ( normally inactive ) ,activated through sequential protease- based step (under particular condition )<br />Complement activator, Complement regulatory protein and Complement receptor<br />
  4. 4. Functions of complement. The major functions of the complement system in host defense are shown. Cell-bound C3b is an opsonin that promotes phagocytosis of coated cells (A); the proteolytic products C5a, C3a, and (to a lesser extent) C4a stimulate leukocyte recruitment and inflammation (B); and the MAC lyses cells (C).<br />
  5. 5. Pathways of Complement Activation <br />3 major pathways of complement activation<br />classical pathway : activated by Ab bound to Ag<br />alternative pathway : activated on microbial cell surfaces in the absence of antibody<br />lectin pathway : activated by plasma lectin that binds to mannose residues on microbes<br />central event in complement activation is proteolysis of C3 to generate biologically active products and subsequent covalent attachment of C3b to microbial cell surfaces or to Ab bound to Ag<br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  6. 6. Overview of the complement pathways indicating components required for recognition, enzymatically active components and complexes, major opsonic, inflammatory and membranolytic products.<br />Rich et al.Clinical immunology principle and practice. third edition.<br />
  7. 7. The early steps of complement activation by the alternative and classical pathways.The alternative pathway is activated by C3b binding to various activating surfaces, such as microbial cell walls, the classical pathway is initiated by C1 binding to antigen-antibody complexes, and the lectin pathway is activated by binding of a plasma lectin to microbes. The C3b that is generated by the action of the C3 convertasebinds to the microbial cell surface or the antibody and becomes a component of the enzyme that cleaves C5 (C5 convertase) and initiates the late steps of complement activation. The late steps of all three pathways are the same (not shown here), and complement activated by all three pathways serves the same functions<br />
  8. 8. Alternative pathway<br />Activation : proteolysis of C3<br />C3 tickover<br />C3b , binding site for factor B covalently tethered to surface of microbial or host cell<br />Bound factor B cleaved by factor D (serine protease)<br />C3 convertase : C3bBb<br />Properdin bind to and stabilize C3bBb complex<br />C5 convertase : C3bBb3b<br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  9. 9. Internal thioester bonds of C3 molecules.A schematic view of the internal thioester groups in C3 and their role in forming covalent bonds with other molecules is shown. Proteolytic cleavage of the α chain of C3 converts it into a metastable form in which the internal thioester bonds are exposed and susceptible to nucleophilic attack by oxygen (as shown) or nitrogen atoms. The result is the formation of covalent bonds with proteins or carbohydrates on the cell surfaces. C4 is structurally homologous to C3 and has an identical thioester group.<br />
  10. 10. The alternative pathway of complement activation.Soluble C3 in plasma undergoes slow spontaneous hydrolysis of its internal thioester bond, which leads to the formation of a fluid-phase C3 convertase (not shown) and the generation of C3b. If the C3b is deposited on the surfaces of microbes, it binds factor B and forms the alternative pathway C3 convertase. This convertase cleaves C3 to produce more C3b, which binds to the microbial surface and participates in the formation of a C5 convertase. The C5 convertase cleaves C5 to generate C5b, the initiating event in the late steps of complement activation<br />
  11. 11. Classical pathway<br /><ul><li>Activate :IgM>IgG3>IgG1>IgG2>>IgG4
  12. 12. C1 : large, multimeric, protein complex
  13. 13. C1q binding site in Cμ3 (IgM),Cγ2 (IgG) domain through its globular head group
  14. 14. C1r, C1s subunits are proteases
  15. 15. Activated C1s cleaves C4, to generate C4b
  16. 16. C2, complexes with C4b and cleaved by C1s to generate soluble C2a and larger C2b fragment
  17. 17. C3 convertase : C4b2b
  18. 18. C5 convertase : C4b2b3b
  19. 19. C5a : potent inflammatory activity
  20. 20. C5b initiate formation of MAC </li></ul>Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  21. 21. Structure of C1.C1q consists of six identical subunits arranged to form a central core and symmetrically projecting radial arms. The globular heads at the end of each arm, designated H, are the contact regions for immunoglobulin. C1r and c1s form a tetramer composed of two c1r and two c1s molecules. The ends of c1r and c1s contain the catalytic domains of these proteins. One c1r2s2 tetramer wraps around the radial arms of the c1q complex in a manner that juxtaposes the catalytic domains of c1r and c1s.<br />
  22. 22. C1 binding to the fc portions of igm and igg. C1 must bind to two or more fc portions to initiate the complement cascade. The fc portions of soluble pentamericigm are not accessible to C1 (A). After igm binds to surface-bound antigens, it undergoes a shape change that permits C1 binding and activation (B). Soluble igg molecules will also not activate C1 because each igg has only one fc region (C), but after binding to cell surface antigens, adjacent iggfc portions can bind and activate C1 (D).<br />
  23. 23. The classical pathway of complement activation.Antigen-antibody complexes that activate the classical pathway may be soluble, fixed on the surface of cells (as shown), or deposited on extracellular matrices. The classical pathway is initiated by the binding of C1 to antigen-complexed antibody molecules, which leads to the production of C3 and C5 convertases attached to the surfaces where the antibody was deposited. The C5 convertase cleaves C5 to begin the late steps of complement activation.<br />
  24. 24. Lectin pathway<br /><ul><li>Activation : D-mannose,GlcNAc ( microbial polysaccharides )
  25. 25. Binding to circulating lectins, eg. Mannose -binding lectin (MBL), or to N-acetylglucosamine recognizing lectins (ficolins ) collectin family and structurally resemble C1q
  26. 26. MASPs eg. MASP-1, 2, and 3 (tetrameric complex similar to C1r and C1s )
  27. 27. MASP-1 cleave C3
  28. 28. MASP-2 cleave C4 and C2
  29. 29. C3 convertase : MASP-1
  30. 30. C5 convertase : C4b2b3b</li></ul>Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  31. 31. Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  32. 32. Activation of the lectin pathway. the lectin activation pathway is engaged by pathogen oligosaccharides (black diamonds ) and leads to a C3 convertase which is identical to that of the classical pathway. MBL serves as the recognition domain of the complex ,while MASP1 and MASP are similar in function to C1r and C1s <br />Middleton’s allergy:principles and practice. 7th edition.<br />
  33. 33. Membrane attack complex<br /><ul><li>Cleavage of C5 into C5a and C5b.
  34. 34. C5 (structurally homologous to C3 and C4, lacks internal thioester bond )
  35. 35. C5b initiates formation of MAC (complex of C5b, C6, C7, C8 and multiple C9 molecules ) binds to C6, and C7 , recruits C8 and complex penetrates more deeply into the membrane.
  36. 36. C9, a pore-forming molecule with homology to perforin. The complex of C5b678 forms a nidus for C9 binding and polymerization
  37. 37. Penetrates membrane bilayers to form pores
  38. 38. Disrupt the osmotic barrier, leading to swelling and lysis of susceptible cells</li></ul>Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  39. 39. Late steps of complement activation and formation of the MAC.Cell-associated C5 convertase cleaves C5 and generates C5b, which becomes bound to the convertase. C6 and C7 bind sequentially, and the C5b,6,7 complex becomes directly inserted into the lipid bilayer of the plasma membrane, followed by stable insertion of C8. Up to 15 C9 molecules may then polymerize around the complex to form the MAC, which creates pores in the membrane and induces cell lysis. C5a released on proteolysis of C5 stimulates inflammation.<br />
  40. 40. A. Complement lesions in erythrocyte membranes are shown in this electron micrograph. The lesions consist of holes approximately 100 Å in diameter that are formed by poly-C9 tubular complexes. B. For comparison, membrane lesions induced on a target cell by a cloned CTL line are shown in this electron micrograph. The lesions appear morphologically similar to complement-mediated lesions, except for a larger internal diameter (160 Å). CTL- and NK cell-induced membrane lesions are formed by tubular complexes of a polymerized protein (perforin), which is homologous to C9 C. A model of the subunit arrangement of the MAC is shown. The transmembrane region consists of 12 to 15 C9 molecules arranged as a tubule, in addition to single molecules of C6, C7, and C8 α and γ chains. The C5bα, C5bß, and C8ß chains form an appendage that projects above the transmembrane pore. <br />Structure of the MAC in cell membranes<br />
  41. 41. Receptors for Complement Proteins<br />CR1 or CD35 : <br />On erythrocyte,neutrophil,monocyte,eosinophil,T and B cell<br />Bind C3b,C4b and promote phagocytosis <br />Opsonization ,activate phagocyte when Fc receptor engaged by Ab coated particle<br />clearance of immune complexes from circulation<br />Regulator of complement activation<br /> CR2 or CD21 :<br />On B lymphocyte, FDC<br />Bind C3d,C3dg and iC3b<br />enhancing B cell activation ( CR2,CD19,TAPA-1 orCD81)<br />promote trapping of Ag-Ab complexes in germinal centers (FDC)<br />Receptor for EBV virus<br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  42. 42.
  43. 43. RECEPTORS FOR COMPLEMENT PROTEINS<br />CR3, CD11bCD18 or Mac-1 :<br />On neutrophil,mononuclearphagocyte,mast cell, NK cell <br />Bind iC3b promote phagocyotsis,ICAM-1 promote attachment to endothelium<br />CR4, p150/95, CD11cCD18 :<br />on dendritic cells<br />binds iC3b<br />function probably similar to Mac-1<br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  44. 44. Receptors for Complement Proteins<br />The complement receptor of the immunoglobulin family (CRIg) <br />on macrophages ( Kupffer cells )<br />integral membrane protein <br />bind C3b and iC3b<br />clearance of opsonized bacteria and other blood-borne pathogens<br />SIGN-R1<br />C-type lectin on marginal zone macrophage<br />recognizes pneumococcal polysaccharides <br />bind C1q, activation of classical complement pathway in an antibody-independent manner<br />opsonization and clearance of pneumococci<br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  45. 45. Regulation of complement activation<br />C1 inhibitor<br />Regulators of the C3 and C5 convertases<br />Factor I<br />Soluble regulatory proteins; C4b-binding protein and factor H<br />Membrane regulatory proteins, CD55 (DAF), CD46 (MCP), CD35 (CR1)<br />Properdin<br />Regulators of the MAC<br />Soluble MAC inhibitors; S protein, and clusterin<br />Membrane MAC inhibitor; CD59<br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  46. 46. C1 inhibitor<br /><ul><li>C1 inhibitor (C1-INH)
  47. 47. serine proteinase inhibitor (serpin) , SERPING1
  48. 48. binds to activated C1r and C1s, limit classical pathway activation.
  49. 49. inhibits MASP-1 and 2, kallikrein, factor XIa, XIIa and plasmin of the lectin pathway and the contact, coagulation, and fibrinolytic systems.
  50. 50. ( Autosimal dominant ) inherited deficiency of C1-INH is basis of hereditary angioedema , plasma level of C1 inh<20-30% of normal </li></ul>Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  51. 51. Serpin inhibitory mechanism. Active serpin(pink) is characterized by a 5-stranded b-sheet (b-sheet A, cyan) and an exposed reactive centre loop (RCL, green)presenting the P1 residue to the active site of the target protease (gold)(a). The initial step is the binding of free protease and active serpin RCL (b). Subsequently, the protease cleaves the RCL. RCL cleavage triggers a profound conformational change within the serpin molecule: the RCL downstream of the scissile bond inserts betweenstrands 3 and 5 of b-sheet A as strand 4, while the protease is translocated to the opposite pole of the inhibitor molecule and deformed, resulting in enzyme inhibition by active-site distortion (c).Therefore, protease-serpinacyl-enzyme complex formation can be viewed generally as biologically irreversible. <br />Trends in Molecular Medicine Vol.15 No.2<br />
  52. 52. Regulation of C1 activity by C1 INH.C1 INH displaces C1r2s2 from C1q and terminates classical pathway activation<br />
  53. 53. Regulators of the C3 and C5 convertases<br />C3b bound by membrane cofactor protein ( MCP ,CD46), CR1, decay-accelerating factor (DAF), factor H<br />C4b bound by DAF, CR1, C4-binding protein (C4BP)<br />competitively inhibit binding of other components of C3 convertase, eg. Bb (alternative pathway ) and C2b ( classical pathway ) , blocking further progression of the complement cascade<br />Factor H inhibits binding of only Bb to C3b <br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  54. 54. The regulation of the classical pathway. The classical activation pathway is shown with the relevant regulatory proteins shown in the gray hexagons. C4 BP denotes C4 binding protein<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  55. 55. The regulation of the alternative pathway. The alternative activation pathway is shown with the relevant regulatory proteins shown in gray hexagons. C3bBb is stabilized by properdin. <br />Middleton’s allergy:principles and practice. 7th edition.<br />
  56. 56. Inhibition of the formation of C3 convertases. Several membrane proteins present on normal cells displace either C2b from the classical pathway C3 convertase (A) or Bb from the alternative pathway C3 convertase (B) and stop complement activation.<br />
  57. 57. Regulators of the C3 and C5 convertases<br /><ul><li>DAF
  58. 58. glycophosphatidylinositol-linked membrane protein
  59. 59. on endothelial cells and erythrocytes.
  60. 60. If deficiency , Causes paroxysmal nocturnal hemoglobinuria.
  61. 61. unusual feature , acquired mutation in defective gene ,in hematopoietic stem cells.
  62. 62. factor I
  63. 63. plasma serine protease degrade cell-associated C3b
  64. 64. active only in presence of regulatory proteins
  65. 65. MCP, factor H, C4BP, and CR1 serve as cofactors
  66. 66. cause dissociation of C3b (and C4b)-containing complexes
  67. 67. Generates iC3b, C3d, and C3dg, recognized by receptors on phagocytes and B lymphocytes</li></ul>Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  68. 68. Factor I-mediated cleavage of C3b. In the presence of cell membrane-bound cofactors (MCP or CR1), plasma factor Iproteolytically cleaves C3b attached to cell surfaces, leaving an inactive form of C3b (iC3b). Factor H and C4-binding protein can also serve as cofactors for factor I-mediated cleavage of C3b. The same process is involved in the proteolysis of C4.<br />
  69. 69. Regulation of formation of the MAC<br />CD59<br />Membrane protein inhibit formation of the MAC <br />glycophosphatidylinositol-linked protein expressed on many cell types.<br />incorporate into assembling MACs after the membrane insertion of C5b-8, thereby inhibiting the subsequent addition of C9 molecules<br />present on normal host cells, where it limits MAC formation, but it is not present on microbes<br />S protein<br />binding to soluble C5b,6,7 complexes <br />Prevent insertion into cell membranes near the site where the complement cascade was initiated <br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  70. 70. Regulation of formation of the MAC. The MAC is formed on cell surfaces as an end result of complement activation. The membrane protein CD59 and S protein in the plasma inhibit formation of the MAC.<br />
  71. 71. COMPLEMENT DEFICIENCIES<br />Genetic deficiencies in classical pathway components<br />Deficiencies in components of the alternative pathway<br />Mutation of the gene encoding the mannose-binding lectin (MBL)<br />Deficiencies in the terminal complement components<br />Deficiencies in complement regulatory proteins<br />Deficiencies in complement receptors<br />Abbaset.al.Cellular&Molecular immunology 6th edition<br />
  72. 72. Genetic deficiencies in classical pathway components<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  73. 73. Genetic deficiencies in classical pathway components<br />C1q deficiency<br />Present with early onset SLE , anti-dsDNA less common ,more severe disease , less steroid responsive<br />Strongest known genetic risk factor for lupus<br />C4 deficiency <br />C4A deficiency , risk factor for SLE (less severity than sufficient complement) early onset SLE , anti-dsDNA less common , <br />C4B deficiency, with invasive bacterial disease <br />Middleton’s allergy:principles and practice. 7th edition.<br />
  74. 74. Genetic deficiencies in classical pathway components<br />C2 deficiency<br />most common of the inherited classical complement component deficiencies in Caucasians<br />most common cause of death : sepsis<br />most common organisms :S. pneumoniae and H. influenzae<br />C3 deficiency<br />rarest of the four early component deficiencies <br />most severe phenotype <br />Membranoproliferativeglomerulonephritis<br />neutrophil dysfunction (abscesses), humoral deficiencies (sinopulmonary disease), and complement deficiencies (sepsis, meningitis). <br />Middleton’s allergy:principles and practice. 7th edition.<br />
  75. 75. Deficiencies in components of the alternative pathway<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  76. 76. Deficiencies in components of the alternative pathway<br />FACTOR B DEFICIENCY <br />single case has been reported ( meningococcemia )<br />FACTOR D DEFICIENCY <br />Neisserial infections are the most common manifestation<br />PROPERDIN DEFICIENCY <br />X-linked complement deficiency<br />one of the more common complement deficiencies and occurs largely in Caucasians<br />one or more episodes of meningococcal disease<br />high fatality rate in contrast to terminal complement component deficiencies<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  77. 77. Mutation of the gene encoding the mannose-binding lectin (MBL)<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  78. 78. GUPTA et al.Indian J Med Res 127, May 2008, pp 431-440<br />
  79. 79. Mutation of the gene encoding the mannose-binding lectin (MBL)<br />MBL DEFICIENCY therapy<br />Plasma derived MBL is now being produced by Co-operative Research Centre for Vaccine Technology (CRC-VT)<br />on phase I safety, tolerability and pharmacokinetics<br />MBL replacement therapy used in 3 situations.<br />where MBL deficiency leads to increased susceptibility of infection, increase resistance to that infection <br />In acute infection,may enhance the resolution of the disease<br />Used to alter the natural history of chronic disease <br />GUPTA et al.Indian J Med Res 127, May 2008, pp 431-440<br />
  80. 80. Deficiencies in the terminal complement components<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  81. 81. Deficiencies in complement regulatory proteins<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  82. 82. C1 inhibitor deficiency<br />Hereditary angioedema<br />mildly increased susceptibility to infection<br />increased risk of SLE<br />Recurrent episodes of angioedema, involvement of airway in absence of anaphylaxis, abdominal episodes, a positive family history, or angioedema arising after trauma<br />Type I deficiency ,most common (85%) of inherited cases<br />Type II deficiency normal production ,but dysfunctional protein<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  83. 83. C1 inhibitor deficiency<br />main manifestations of C1 inhibitor deficiency are recurrent episodes of submucosal or subcutaneous edema<br />severity of episodes do not correlate with laboratory features<br />extremities, face, or genitalia are most often involved<br />The most feared type of angioedema is that involving the airway<br />angioedema typically progresses for 1–2 days and resolves in another 2–3 days. Common precipitants are illness, hormonal fluctuations, trauma, and stress<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  84. 84. Contact system<br />
  85. 85. pathogenesis of angioedemadue to C1-INH deficiency. In HAE, the deficiency of C1-INH is due to a mutation in the C1-INH gene, which impairs C1-INH synthesis or function. In AAE, C1-INH deficiency is due to the cleavage of C1-INH by autoantibodies or to its consumption by neoplastic, mainly lymphoproliferative, tissue. Reduced C1-INH plasma levels result in hyperactivation of the classical complement pathway with increased consumption of C1-INH and further reduction of its plasma level. Impaired inhibition of activated Factor XII (FXIIa) and kallikrein, as a result of a lack of their principal inhibitor C1-INH, enables cleavage of high molecular weight kininogen (HK) by kallikrein and release of bradykinin, which binds to its B2 receptors, causing edema<br />Tissue permeability<br />vasodilatation<br />
  86. 86. Acquired C1 inhibitor deficiency<br />clinically indistinguishable from inherited<br />that the age of onset is after 30 years<br />The laboratory features are similar to those of hereditary C1 inhibitor deficiency except that C1q levels are diminished in these patients<br />B cell malignancies and monoclonal gammopathies are the most common<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  87. 87. Trends in Molecular Medicine Vol.15 No.2<br />
  88. 88. CD59 DEFICIENCY AND PAROXYSMAL NOCTURNAL HEMOGLOBINURIA<br />PNH : <br />recurrent episodes of hemoglobinuria due to intravascular hemolysis<br />Thrombosis occurs for unknown reasons<br />aplastic anemia <br />due to acquired somatic mutations of PIG-A or PIG-M in a clone of bone marrow progenitor cells<br /> These protein products are required for GPI-anchored proteins and C8-binding protein, DAF and CD59 are all GPI-anchored proteins which protect hematopoietic cells from complement-mediated lysis<br />DAF deficiency does not have a hemolytic phenotype<br />CD59 is more important <br />Middleton’s allergy:principles and practice. 7th edition.<br />
  89. 89. Deficiencies in complement receptors<br />Middleton’s allergy:principles and practice. 7th edition.<br />
  90. 90. CR3/CR4 deficiency<br />β2-integrin deficiency is leukocyte adhesion deficiency type I (LAD type I)<br />Mutations in the common chain (CD18)<br />LAD type I is very serious disorder with high mortality rate<br />Very high resting wbc counts, frequent necrotic skin infections without pus formation, delayed separation of umbilical cord, and assorted other serious bacterial and fungal infections<br />bone marrow transplantation is recommended ( severe case ) <br />Middleton’s allergy:principles and practice. 7th edition.<br />
  91. 91. conclusion<br />Middleton’s allergy:principles and practice. 7th edition<br />
  92. 92. J ALLERGY CLIN IMMUNOL . APRIL 2004<br />
  93. 93. Thank you<br />

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