Complement associated immune disorder Dr Chen Hung Chen

Complement associated immune disorder Dr. Chen Hung Chen ( 陳 政 宏 ) Division of Rheumatology, Immunology and Allergy Department of Internal medicine Tri-Service General Hospital

Introduction of Complement system: Definition: • A group of sequentially reacting proteins, which upon activation, mediate a number of biological reactions important to host defense Nomenclature: • • • “C”-designation for 11 of complement proteins( C 1, C 2, etc) “Factor”-designation for many alternative pathway components( factor B) Overbar-indicates an enzymatically active protein or complex Lower case letters-indicates a proteolytic cleavage fragments(C 3 a, C 5 a) “R”-designation for receptors in the complement system(CR 1, CR 2)

Complement Biosynthetic Sites • • • Hepatocytes Monocyte/Macrophage Hematopoietic Fibroblasts Endothelial Reproductive Adipocytes Astrocytes Neurons

Modular Structure of Complement Proteins • Enzymes-(Serine Protease Domain) C 1 s, C 1 r, C 2, MASP 1/2, factor B, D, I • Collectins-(Collagen Stalk, Gobular Domain) C 1 q, MBL, Ficolin • Cytolytic-(C 9/Perforin Domain) C 6, C 7, C 8, C 9 • Regulatory and Receptor (SCR Domain) DAF, MCP, C 4 BP, CR 1 & factor H • “True” Complement Proteins C 3, C 4, C 5

Protein of the Complement System Serum Soluble Membrane Bound Activation Regulation C 1 q, C 1 r, C 1 s, C 2 -C 9, Factor B & D, MASP-1/2 s. MAP, ficolin C 1 -INH, C 4 BP Factor H & I Properdin, S protein(vitrone ctin), Sp 40(clusterin) CR 1, CD 59, DAF(CD 55), MCP(CD 46) Receptors CR 1 -CR 4 C 3 a. R, C 5 a. R C 1 q. R

Complement Activation • Classical Pathway. Ag-Ab complexes • Mannan-Binding Lectin Pathway. Mannose, N-acetylglucosamine • Alternative Pathway. LPS, lipopolysaccharides

Complement-fixing potential of Ab: Ig. M>Ig. G 3>Ig. G 1>Ig. G 2>Ig. G 4

Transmission EM of the C 1 q (left) and C 1 r-C 1 s complex (right)

Properdin (C 3 a. Bb. P) (C 3 b. Bb. C 3 b. P)

(Potent chemotactant)

Initiates the assembly of MAC “Classic doughnut hole formation”

(C 4 b 2 a) (C 4 b 2 a 3 b ) (Initiates by C 3 b 5 b) C 3 convertases C 5 convertases (C 3 b. Bb. C 3 b. P)

Complement regulatory proteins & primary location Fluid phase -C 1 -INH -Factor I, H, C 4 -bp, S protein (vitronectin), SP-40 (clusterin) -Carboxypeptidase Cell membrane -DAF (CD 55) -MCP (CD 46) -Protectin (CD 59), membrane C 3 -proteinase Matrix -Decorin

Complement Activation Regulation CLASSIC MBP C 4 -bp: Cofactor I C 1 -INH: inactivate C 1 r, C 1 s, MASPs Factor I: inactivate C 3 b, C 4 b Factor H: cofactor for Factor I DAF(CD 55): Bind C 3&C 5 convertase MCP(CD 46): cofactor I, bind C 3& C 5 convertase CR 1(CD 35): combine activities of factor H, C 4 bp, MCP & DAF C 3 a Carboxypeptidas e: inactivate C 3 a & C 5 a ALTERNATIVE C 3 b Vitronectin: Bind C 5 b 67 & C 9 to prevent membrane insertion Protectin(CD 59): Bind C 5 b-8, C 5 b-9 to prevent pore formation C 5 a C 5 b+C 6 -9(MAC)

Clinical relevant biologic activities of complement Foreign organism, antigen RBC Tumor cells Blood vessels Heart Reproduction Lymphocyte Opsoniztion for phagocytosis by PMN, Monocyte, macrophage, lysis; in vivo trafficking Lysis( intavascular or extravascular) Immune complex trafficking Promotion of ADCC activity Promotion of NK activity Lysis Atherosclerosis Ischemia-reperfusion injury Antibody-mediated infertility, recurrent fetal loss Coactivation, antigen present

Autoimmune and/or inflammatory disease Renal CNS Joints Platelets Blood vessels Skin Pulmonary Xenotransplantation Allotransplantation Mediates GN, proteinuria, stimulation of collagen & cytokine synthesis & cellular influx Demyelination in MS, Ab-mediated neuropathies Alzheimer’s disease Recruitment & activation of PMNs Activation of clotting pathway; Immune thrombocytopenia Immune complex vasculitis; neutrophil chemotaxis, binding and activation Ab-mediated inflammation ARDS by anaphylatoxin-mediated neutrophil activation Hyperacute rejection Chronic rejection

Inflammatory Disorder associated with Complement Activation • Severe trauma, burn, sepsis • • Systemic inflammatory • reaction syndrome (SIRS) • • Adult respiratory distress syndrome (ARDS) • • Multiple organ dysfunction • syndrome (MODS) • • Ischemia reperfusion injury • • Angioedema, capillary leakage syndrome Hyperacute graft rejection Vasculitis, nephritis Autoimmune disorder, systemic lupus erythematosus Rheumatoid arthritis Multiple sclerosis Alzheimer’s disease Reaction to dialysis, apheresis, cardiopulmonary bypass

Vasculitis & Immune complex disease • Local deposition of C 3, C 5 b-9 and/or alternative pathway components. • Evidence of systemic depletion ( low C 3, C 4 or THC ) • Associated Disease: Immuneocomplexes disease, PAN, hypersensitivity vasculitis, vasculitis and GN in SLE HSP( alternative pathway activation: C 3, properdin with Ig. A) except: Wegener’s or lymphomatoid granulomatosis: no local complement deposition or systemic depletion

Rheumatoid arthritis Synovial fluid: ↓THC, ↑C 3 d, C 3 a, C 5 b-9 Pulmonary disease C 3 a and C 5 a induce neutrophils activation pulmonary injury MAC stimulating endothelial cell relieve thromboxanes increase adhesion molecule expression & pulmonary hypertensive change SLE with interstitial lung disease C 1 q, C 3 with Ig. G, Ig. M deposition

Renal disease Protective role: trafficking of ICs from kidney by binding to CR 1 on RBC Detrimental role: complement activation without cell reflux (membranous), with cell reflux (membranoproliferative) e. g. : In MPGN, ↑C 3 nephritic factor C 5 b-9 on cells increase collagen synthesis & thromboxanes and other proliferative molecules

Platelet disease: ITP C 5 b-9 has potentially profound effects on its functionincrease thromboxane synthesis, activation of protein kinase C and myosin light-chain kinase Hemolytic anemia: Intravascular hemolytic anemia: alloimmunization during prior transfusions Extravascular hemolysis : in liver & spleen of opsonized cells by Fc & complement receptor HUS: 1/3 pts have hypocomplementemia & poor prognostic indicator

Myocardial disease: ↑serum complement activation products in unstable angina ↑C 3, C 4, C 5 b-9 & ↓CD 59 & DAF in infracted zone reperfusion injury cause complement activation Atherosclerosis: C 5 b-9 & activated C 3 found in lesion, ↑complement regulatory protein expression on Mac in lesion C 5 a promote peripheral vasoconstriction

Cutaneous disease: SLE: C 3 with Ig deposition(even in non-involved area) Evidence of complement activation: Autoimmune bullous disease(Pemphigus, bullous pemphigoid, epidermolysis bullosa) Acne: C 3 in basement zones Psoriasis: C 3 a, C 5 a in lesion & complement activated products in serum

Reproduction & pregnancy: Complement-fixing antibodies with specificity for paternal determinants on sperm mediate infertility High levels of complement regulatory protein on reproductive system prevent uncontrolled complement activation (e. g. : DAF, MCP, CD 59) Myositis: DM : C 5 b-9 with Ig. G, Ig. M, C 3 deposition in venules & arterioles PM: C 5 b-9 in muscle fiber

Neurologic disease: Asceptic meningitis : ↑in C 3, C 4: CSF/plasma index MS’s CSF: ↑C 3 a, C 4 a & ↓C 9 SLE’s CSF : ↑C 5 b-9 Alzheimer’s disease: ↑C 4 d, C 1 q & C 5 b-9 in brain

Xenotransplantation: Immediate hyperacute rejection: mediated by performed Abs and/or complement Chronic rejection: unclear Tumor resistance to complement: Increase complement regulatory protein level in some malignancies, e. g. MCP, DAF, CD 59 provide tumor cells to escape the evasion of Ab or enhanced ADCC & NK activity mediated by C 3 b and/or C 3 bi bound to the tumor cell

Disease in which complement inhibitors will probably be effective • Some forms of vasculitis • RA • ARDS • SLE • Many types of renal diseases • ITP • Hemolytic anemia • Myocardial infacion • Neurologic disease( possibly Alzheimer’s disease) • Ischemia-reperfusion injury • Antiphospholipid syndrome & recurrent fetal loss • Ab-mediated cutaneous disease • Xenotransplant rejection • Allotransplant rejection(? Accelerated atherosclerosis)

Selected Complement Activation Inhibitors Under Development Product TPO 10, TPO 20 Description s. CR 1 without(TPO 10) or with s. Le* TPO 20 Actions Degrade C 3 b/C 4 b, decay C 3 & C 5 convertase, TPO 20 Company Avant Immunotherapeutics (Needham, MA) block selectin binding h 5 G 1. 1 APT 070 CAB-2 Humanized, high-affinity anti-C 5 m. Ab Blcok cleavage of C 5 to C 5 a & Alexion Pharmaceuticals as single-chain Fv or intact m. Ab C 5 b by C 5 convertase (New Haven, CT) Amino-terminal 3 SCR of CR 1 Inserts in cell membranes and Ad. Pro. Tech myristoylated at the carboxyl provides intrinsic protection (Royston, Herts, UK) terminus via CR 1 -like mechanisms Soluble recombinant chimera of Degrades C 3 b/C 4 b and MCP & DAF C 1 q RNA aptamers decays C 3 & C 5 convertases Small molecule inhibitors of C 1 q Block C 1 q Millenium Pharmaceuticals (Cambridge, MA) Ne. Xstar Pharmaceuticals (Boulder, CO) C 1 q analogs Low-molecular-weight inhibitor of Block C 1 q Gliatech(Cleveland, OH) Inhibit AP activation Bio. Cryst Pharmaceuticals beta-amyloid-induced activation of C 1 q Serine protease Low-molecular-weight inhibitors of factor D (Hoover, AL)

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