13. Complement Component PDF

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IMMUNOLOGY SEROLOGY COMPLEMENT COMPLEMENT it is a normal component of made up of either or it enhances the mechanism against foreign cells it completes the action of Antibodies towards the Antigen made up of 30 soluble proteins: has 9 major complement C2 C3, C4, C5, C6, C7, C8, C9 C3 most abundant c...

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IMMUNOLOGY & SEROLOGY

COMPLEMENT COMPLEMENT (C’) - it is a normal component of serum/plasma made up of either α-globulins or β-globulins - it enhances the host-defense mechanism against foreign cells - it completes the action of Antibodies towards the Antigen - made up of 30 soluble & cell-bound proteins: - has 9 major complement components—C1, C2 C3, C4, C5, C6, C7, C8, C9  C3 - most abundant complement component - major complement component - Normal value: 1,200-1,400 µg/mL - Molecular weight: 180 kda  C4 - 2nd most abundant complement component - Normal value: 450-600 µg/mL - Molecular weight: 210 kda - the remaining 21 complement component falls on the..  REGULATORY & INHIBITORY: - maintains the balance of the complement system - prevents overactivation/underactivation of the complement system - has two forms:  ZYMOGEN: inactive form of complement  SERINE PROTEASE: active form f complement VITAL FUNCTIONS OF COMPLEMENT SYSTEM: 1. Host-defense mechanism  Opsonization  Chemotaxis & Leukocyte activation  Lysis of bacterial & mammalian cells  Stimulation of inflammatory response 2. Interface between Innate & Adaptive immunity  Augmentation ofantibodyresponse  Enhancement of immunologic memory 3. Disposal of wastes  Clearance or removal of “Immune complexes” (Ag-Ab complexes) from tissues 4. Involve in Coagulation process ROUTES / PATHWAYS OF COMPLEMENT ACTIVATION: 1. CLASSICAL PATHWAY - proteins termed as “Components” & are symbolized by the letter “C” followed by a number - has three stages: a. INITIATION / RECOGNITION b. AMPLIFICATION / ENZYMATIC DESTRUCTION c. MEMBRANE ATTACK leading to cell destruction

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

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OLFU VALENZUELA

IMMUNOLOGY & SEROLOGY

COMPLEMENT 2. ALTERNATIVE PATHWAY - normal serum proteins are termed as “Factors” & are symbolized by letters essential in the initiation of this:  FACTOR B: analogous to C2  FACTOR D: believed to be similar to C1s  PROPERDIN: a γ-globulin which when complexed with C3b stabilizes the alternate pathway C3-convertase 3. MANNOSE BINDING LECTIN (MBL) PATHWAY - MBL is a member of the so-called “Collectin family of molecules” - structurally similar to C1q as it functions as an Opsonin - In this pathway, the interaction of MBL with a carbohydrate on the surface of polysaccharide of microbes leads to the formation of enzymatic complex that binds & activates C4 & C2  MBL: analogous to C1q  MASP-1: similar to C1r  MASP-2: related to C1s CLASSICAL PATHWAY part of Humoral Immunity IMMUNOLOGIC ACTIVATORS: major activator - IgM, IgG3, IgG1, IgG2 bound to antigen - bacteria like E.coli, Klebsiella, Mycoplasma - Parasites like Trypanosoma & Schistosoma NON-IMMUNOLOGIC ACTIVATORS: minor activator - Apoptotic cells, Staphylococcal Protein A, DNA, CRP bound to Ligand, certain viruses & g(-) bacteria possess a recognition unit - requires presence of Calcium - requires C1, C2, & C4 for its activation

ALTERNATIVE PATHWAY (Alternate, By-pass, Primitive, & Properdin Pathway) part of Natural Immunity IMMUNOLOGIC ACTIVATORS: minor activator - Aggregated IgA - in some instances, IgG4 & IgE NON-IMMUNOLOGIC ACTIVATORS: major activator - bacterial & plant polysaccharide, viruses & tumor cells, parasites like Trypanosome, Zymosan, Inulin, Cobra venom factor, especially Lipopolysaccharide of g(-) bacteria has no recognition unit - lack of dependence to Calcium - activation immediately starts with C3

MAIN SOURCES OF COMPLEMENT PROTEINS: - Hepatocytes, Intestinal & Urogenital epithelial cells; Monocytes, & Macrophages - All are produced in the liver except for:  C1 = Intestinal cells  C7 Monocytes, Macrophage, Neutrophils  Properdin * Many complement components are localized in the MHC:  Factor B MHC class III  C2  C4 - Homeostatic maintenance of complement activation is mediated by Regulatory Proteins:  On Plasma / “Fluid phase inhibitor”  Anaphylatoxin inhibitor  C1 inhibitor: dissociates C1r & C1s from C1q  FACTOR I: cleaves C4 & C3

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

|

OLFU VALENZUELA

IMMUNOLOGY & SEROLOGY

COMPLEMENT  FACTOR H - major inhibitor - co-factor with Factor-I to inactivate C3b - competes with Factor-B in binding site of C3b  C4 BINDING PROTEIN - inactivates C4b - co-factor with Factor-I to cleave C4  S PROTEIN / VITRONECTIN - prevents attachment of C5b678 complex to cell membrane  On Cells / “Cell bound regulator” – protects cell from By-stander lysis  DECAY ACCELERATING FACTOR (DAF) / CD55 - dissociates C3-convertase - found on RBC  MEMBRANE INHIBITOR OF REACTIVE LYSIS (MIRL) - inhibits Membrane Attack Complex (MAC) In-vitro destruction of complement:  Addition of chelating agents such as EDTA—can chelate Calcium  Inactivation of serum— @ 56°c for 30mins  Treatment with Zymosan DIAGNOSTIC EVALUATION OF COMPLEMENT: 1. NEPHELOMETRY: Serum/Plasma Assay of C3 & C4 2. C1 BINDING ASSAY - measures the binding of immune complexes containing IgG1, IgG2, IgG3, and/or IgM to C1q - it can be useful prognostic tool @ diagnosis & during remission of Acute Myelogenous Leukemia 3. HEMOLYTIC TITRATION ASSAY - use Ch50 for Class Pathway & AH50 for Alternative Pathway in order to measure amount of serum required to lyse - 50% of reagent red cell 4. COMPLEMENT FIXATION TEST DEFICIENT ASSOCIATED DISEASE - Specimen: Inactivated serum COMPONENT - SLE-like syndrome - Unknown: Antibody C1 - recurrent infections a. TEST SYSTEM - SLE-like syndrome - Ag & Ab C2 - recurrent infections - Sheep RBC coated with Hemolysis C4 - SLE-like syndrome b. INDICATOR SYSTEM - Glomerulonephritis C3 (+) Result: no Hemolysis - severe recurrent infections Ag + Ab Ag + Ab (-) Result: with Hemolysis Factor H / Factor I - recurrent Pyogenic infections complex (Guinea pig / Rabbit C9 ** NO KNOWN DISEASE* serum) C1 Inhibitor - Hereditary Angioedema C5-C8 - Neisseria infection Properdin - Neisseria infection - Neisseria infections - Pneumococcal disease MBL - Sepsis MASP-2 - Pneumococcal disease - Paroxysmal Nocturnal DAF Hemoglobinuria JOYCE ANN S. MAGSAKAY BS MEDICAL LABORATORY SCIENCE | OLFU VALENZUELA - Paroxysmal|Nocturnal MIRL

IMMUNOLOGY & SEROLOGY

COMPLEMENT ANAPHYLATOXIN OPSONIN CHEMOTAXIN PURFURATION LYTIC COMPONENT IONS C3-CONVERTASE C5-CONVERTASE

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

C4a, C3a, C5a C3b C5a C5b C8 C1 = Calcium C3-convertase = Magnesium C4b2a = Classical Pathway C3bBb = Alternative Pathway C4b2a3b = Classical Pathway C3bBb3b = Alternative Pathway

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