Complement Cascade Lecture Notes PDF

SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE  ✓ Describe the of the complement system ✓ Differentiate between the L...

SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE  ✓ Describe the of the complement system ✓ Differentiate between the LEARNING and indicate proteins and activators for each. OBJECTIVES ✓ Describe of the complement system and their roles. By the end of the lesson, the ✓ Discuss the students are expected to:. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY  SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE TOPIC IMMUNOLOGY & SEROLOGY OUTLINE ▪ Major Proteins of the Complement System ▪ Functions ▪ Pathways of Activation ▪ Biologic sequence of activation ▪ Regulation DEFINITION COMPLEMENT ▪ First described by Paul Ehrlich ▪ Jules Bordet described the nature of complement ▪ Innate immune response ▪ A group of over 30 regulatory glycoproteins found in circulation or bound to membranes. ▪ Work by enzymatically (proteinases) destroying targets such as cells and bacteria. ▪ Most complement plasma proteins are produced in the liver (acute phase reactant). SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY EXPERIMENT COMPLEMENT SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY GENERAL CHARACTERISTICS COMPLEMENT ▪ Heat –labile series of more than 30 soluble plasma proteins ▪ Complement is deactivated when heated to 56°C for 30 minutes. ▪ Major fraction of beta globulins SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY FUNCTION COMPLEMENT ▪ Opsonization ▪ Chemotaxis ▪ Anaphylaxis ▪ Lysis of cells/bacteria ▪ Immune complex removal ▪ B-cell activation SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspective. F.A. Davis. IMMUNOLOGY & SEROLOGY ▪ Turgeon, M. L. (2018). Immunology & serology in laboratory medicine (Sixth edition). Elsevier. NOMENCLATURE COMPLEMENT ▪ Named with a capital C and a number: ▪ Ex. C1, C2 ▪ Numbered according to an order of discovery (not based on the order of activation) ▪ Small letter after the number: ▪ Ex. C4b, C4a ▪ Indicates that the protein is the smaller portion of a large precursor as a result of cleavage by proteases ▪ Smaller fragment: indicated by the small letter “a” ▪ Larger fragment: indicated by small letter “b” SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY NOMENCLATURE COMPLEMENT ▪ Named with a capital C and a number: ▪ Ex. C1, C2 ▪ Numbered according to an order of discovery (not based on the order of activation) ▪ Small letter after the number: ▪ Ex. C4b, C4a ▪ Indicates that the protein is the smaller portion of a large precursor as a result of cleavage by proteases ▪ Smaller fragment: indicated by the small letter “a” ▪ Larger fragment: indicated by small letter “b” SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY NOMENCLATURE COMPLEMENT ▪ Exception of the rule: ▪ C2 fragments ▪ “a” fragment = LARGER ▪ “b” fragment = SMALLER SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SOURCE COMPLEMENT ▪ Most complement proteins are produced in the LIVER Except: ▪ C1: produced by intestinal epithelial cells ▪ Factor D: produced by adipose tissues ▪ Macrophages and Monocytes: additional sources of C1, C2, C3, and C4 ▪ The rest of the components ▪ Acts as stabilizers and control proteins, and proteases SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY PATHWAYS COMPLEMENT ▪ Involves three separate pathways: ▪ Classical pathway ▪ Alternative pathway (a.k.a Properdin pathway) ▪ Mannose-binding lectin (MBL) pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE: CLASSICAL PATHWAY COMPLEMENT CLASSICAL PATHWAY ▪ It is triggered by the binding of antibodies, usually IgG or IgM, to antigens on a cell surface, such as a bacterial cell. ▪ Complement binds to CH2 domain in antibodies (Fc region) ▪ All IgM can fix complement ▪ All IgG can fix complement except IgG4 ▪ Needs at least 2 monomers of IgG attached to target cells SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY COMPLEMENT CLASSICAL PATHWAY ▪ It is triggered by the binding of antibodies, usually IgG or IgM, to antigens on a cell surface, such as a bacterial cell. ▪ Complement binds to CH2 domain in antibodies (Fc region) ▪ All IgM can fix complement ▪ All IgG can fix complement except IgG4 ▪ Needs at least 2 monomers of IgG attached to target cells SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY COMPLEMENT CLASSICAL PATHWAY ▪ It is triggered by the binding of antibodies, usually IgG or IgM, to antigens on a cell surface, such as a bacterial cell. ▪ Complement binds to CH2 domain in antibodies (Fc region) ▪ All IgM can fix complement ▪ All IgG can fix complement except IgG4 ▪ Needs at least 2 monomers of IgG attached to target cells SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY RECOGNITION UNIT CLASSICAL PATHWAY ▪ Recognition unit: C1qrs (C1q, C1r, and C1s). ▪ Calcium-dependent ▪ C1q is a large, hexameric protein with six globular heads and a tail that resembles a collagen molecule. ▪ Each globular head of C1q can bind to the Fc region of an antibody. ▪ At least two Fc regions must be bound for the classical pathway to be activated. ▪ Single IgM molecule ▪ Two IgG molecules SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Activated C1s cleaves the complement proteins C4 and C2. ▪ C4 is cleaved first, and the larger fragment, C4b, binds to the cell surface near the C1 complex. ▪ C2 then binds to C4b, and C1s cleaves C2, forming the C4b2a complex SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Activated C1s cleaves the complement proteins C4 and C2. ▪ C4 is cleaved first, and the larger fragment, C4b, binds to the cell surface near the C1 complex. ▪ C2 then binds to C4b, and C1s cleaves C2, forming the C4b2a complex SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Activated C1s cleaves the complement proteins C4 and C2. ▪ C4 is cleaved first, and the larger fragment, C4b, binds to the cell surface near the C1 complex. ▪ C2 then binds to C4b, and C1s cleaves C2, forming the C4b2a complex SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Activated C1s cleaves the complement proteins C4 and C2. ▪ C4 is cleaved first, and the larger fragment, C4b, binds to the cell surface near the C1 complex. ▪ C2 then binds to C4b, and C1s cleaves C2, forming the C4b2a complex SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Activated C1s cleaves the complement proteins C4 and C2. ▪ C4 is cleaved first, and the larger fragment, C4b, binds to the cell surface near the C1 complex. ▪ C2 then binds to C4b, and C1s cleaves C2, forming the C4b2a complex SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ The activation unit is initiated when the activated C1s protease cleaves C4 into C4a and C4b. ▪ C2 then binds to the surface-bound C4b, forming the C4b2 complex (C3 convertase). ▪ The C3 convertase cleaves the abundant complement protein C3 into C3a, a small anaphylactic peptide, and C3b. ▪ C3b can then bind to the cell surface near the C4b2a complex, similar to C4b. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ The activation unit is initiated when the activated C1s protease cleaves C4 into C4a and C4b. ▪ C2 then binds to the surface-bound C4b, forming the C4b2 complex (C3 convertase). ▪ The C3 convertase cleaves the abundant complement protein C3 into C3a, a small anaphylactic peptide, and C3b. ▪ C3b can then bind to the cell surface near the C4b2a complex, similar to C4b. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ The activation unit is initiated when the activated C1s protease cleaves C4 into C4a and C4b. ▪ C2 then binds to the surface-bound C4b, forming the C4b2 complex (C3 convertase). ▪ The C3 convertase cleaves the abundant complement protein C3 into C3a, a small anaphylactic peptide, and C3b. ▪ C3b can then bind to the cell surface near the C4b2a complex, similar to C4b. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Some of the C3b molecules bind to C4b2a, forming the C4b2a3b complex (C5 convertase). ▪ The C5 convertase cleaves C5 into C5a and C5b. ▪ C5b binds to the cell surface, where it initiates the assembly of the MAC. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Some of the C3b molecules bind to C4b2a, forming the C4b2a3b complex (C5 convertase). ▪ The C5 convertase cleaves C5 into C5a and C5b. ▪ C5b binds to the cell surface, where it initiates the assembly of the MAC. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Some of the C3b molecules bind to C4b2a, forming the C4b2a3b complex (C5 convertase). ▪ The C5 convertase cleaves C5 into C5a and C5b. ▪ C5b binds to the cell surface, where it initiates the assembly of the MAC. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Some of the C3b molecules bind to C4b2a, forming the C4b2a3b complex (C5 convertase). ▪ The C5 convertase cleaves C5 into C5a and C5b. ▪ C5b binds to the cell surface, where it initiates the assembly of the MAC. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT CLASSICAL PATHWAY ▪ Some of the C3b molecules bind to C4b2a, forming the C4b2a3b complex (C5 convertase). ▪ The C5 convertase cleaves C5 into C5a and C5b. ▪ C5b binds to the cell surface, where it initiates the assembly of the MAC. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY MEMBRANE ATTACK COMPLEX CLASSICAL PATHWAY ▪ C5b binds to C6, and this complex binds to C7. The C5b-C6-C7 complex then binds to C8, and finally, multiple C9 molecules polymerize to form a pore in the cell membrane. ▪ This pore, known as the Membrane Attack Complex, disrupts the integrity of the cell membrane, leading to the influx of water and ions, and ultimately, cell lysis SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY MEMBRANE ATTACK COMPLEX CLASSICAL PATHWAY ▪ C5b binds to C6, and this complex binds to C7. The C5b-C6-C7 complex then binds to C8, and finally, multiple C9 molecules polymerize to form a pore in the cell membrane. ▪ This pore, known as the Membrane Attack Complex, disrupts the integrity of the cell membrane, leading to the influx of water and ions, and ultimately, cell lysis SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY MEMBRANE ATTACK COMPLEX CLASSICAL PATHWAY ▪ C5b binds to C6, and this complex binds to C7. The C5b-C6-C7 complex then binds to C8, and finally, multiple C9 molecules polymerize to form a pore in the cell membrane. ▪ This pore, known as the Membrane Attack Complex, disrupts the integrity of the cell membrane, leading to the influx of water and ions, and ultimately, cell lysis SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY MEMBRANE ATTACK COMPLEX CLASSICAL PATHWAY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SUMMARY CLASSICAL PATHWAY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE: ALTERNATIVE PATHWAY DEFINITION ALTERNATIVE PATHWAY ▪ The alternative pathway is activated directly by the presence of certain molecules on the surface of microorganisms. ▪ bacterial cell walls (lipopolysaccharide), fungal cell walls, yeast, viruses, virally infected cells, tumor cell lines, and some parasites (trypanosomes). ▪ This antibody-independent activation makes the alternative pathway a rapid and efficient first line of defense against infection. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY RECOGNITION UNIT ALTERNATIVE PATHWAY ▪ C3 is spontaneously hydrolyzed by water to produce C3b, which binds Factor B and together they attach to target cell surface. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY RECOGNITION UNIT ALTERNATIVE PATHWAY ▪ C3 is spontaneously hydrolyzed by water to produce C3b, which binds Factor B and together they attach to target cell surface. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY RECOGNITION UNIT ALTERNATIVE PATHWAY ▪ C3 is spontaneously hydrolyzed by water to produce C3b, which binds Factor B and together they attach to target cell surface. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY RECOGNITION UNIT ALTERNATIVE PATHWAY ▪ C3 is spontaneously hydrolyzed by water to produce C3b, which binds Factor B and together they attach to target cell surface. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY RECOGNITION UNIT ALTERNATIVE PATHWAY ▪ C3 is spontaneously hydrolyzed by water to produce C3b, which binds Factor B and together they attach to target cell surface. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ B is cleaved by Factor D into the fragments Ba and Bb. ▪ Bb combines with C3b to form C3bBb, an enzyme with C3 convertase activity. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ B is cleaved by Factor D into the fragments Ba and Bb. ▪ Bb combines with C3b to form C3bBb, an enzyme with C3 convertase activity. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ More C3 is cleaved, forming more C3bBb. ▪ This enzyme is stabilized by properdin, and it continues to cleave additional C3. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ More C3 is cleaved, forming more C3bBb. ▪ This enzyme is stabilized by properdin, and it continues to cleave additional C3. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ More C3 is cleaved, forming more C3bBb. ▪ This enzyme is stabilized by properdin, and it continues to cleave additional C3. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY ACTIVATION UNIT ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY MEMBRANE ATTACK COMPLEX ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY MEMBRANE ATTACK COMPLEX ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY MEMBRANE ATTACK COMPLEX ALTERNATIVE PATHWAY ▪ If a molecule of C3 remains attached to the C3bBbP enzyme, the convertase now has the capability to cleave C5. ▪ The C5 convertase thus consists of C3bBbP3b. ▪ After C5 is cleaved, the pathway is identical to the classical pathway SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SUMMARY ALTERNATIVE PATHWAY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE: LECTIN PATHWAY COMPLEMENT CASCADE LECTIN PATHWAY ▪ The lectin pathway is initiated when mannose-binding lectin (MBL) binds to mannose or related sugars found on various microorganisms. ▪ MBL is similar in structure to C1q of the classical pathway. ▪ Once MBL binds to a microbe, MBL-associated serine proteases, MASP-1, MASP-2, and MASP-3 bind to the MBL. ▪ This complex of molecules activates MASP-2. ▪ MASP-2 then cleaves complement components C4 and C2, just as in the classical pathway. ▪ From this point forward, the lectin pathway is identical to the classical pathway. ▪ Both pathways proceed to the formation of the membrane attack complex. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE LECTIN PATHWAY ▪ The lectin pathway is initiated when mannose- binding lectin (MBL) binds to mannose or related sugars found on various microorganisms. ▪ MBL is similar in structure to C1q of the classical pathway. ▪ Once MBL binds to a microbe, MBL-associated serine proteases, MASP-1, MASP-2, and MASP- 3 bind to the MBL. ▪ This complex of molecules activates MASP-2. ▪ MASP-2 then cleaves complement components C4 and C2, just as in the classical pathway. ▪ From this point forward, the lectin pathway is identical to the classical pathway. ▪ Both pathways proceed to the formation of the membrane attack complex. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE LECTIN PATHWAY ▪ The lectin pathway is initiated when mannose- binding lectin (MBL) binds to mannose or related sugars found on various microorganisms. ▪ MBL is similar in structure to C1q of the classical pathway. ▪ Once MBL binds to a microbe, MBL-associated serine proteases, MASP-1, MASP-2, and MASP- 3 bind to the MBL. ▪ This complex of molecules activates MASP-2. ▪ MASP-2 then cleaves complement components C4 and C2, just as in the classical pathway. ▪ From this point forward, the lectin pathway is identical to the classical pathway. ▪ Both pathways proceed to the formation of the membrane attack complex. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE LECTIN PATHWAY ▪ The lectin pathway is initiated when mannose- binding lectin (MBL) binds to mannose or related sugars found on various microorganisms. ▪ MBL is similar in structure to C1q of the classical pathway. ▪ Once MBL binds to a microbe, MBL-associated serine proteases, MASP-1, MASP-2, and MASP- 3 bind to the MBL. ▪ This complex of molecules activates MASP-2. ▪ MASP-2 then cleaves complement components C4 and C2, just as in the classical pathway. ▪ From this point forward, the lectin pathway is identical to the classical pathway. ▪ Both pathways proceed to the formation of the membrane attack complex. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SUMMARY LECTIN PATHWAY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SUMMARY COMPLEMENT CASCADE SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE IMMUNOLOGY & SEROLOGY COMPLEMENT CASCADE: REGULATORS REGULATORS OF THE COMPLEMENT CASCADE C1-INH (C1 INHIBITOR) ▪ Regulatory protein of the classical and lectin pathways. ▪ It prevents the complement cascade from spiraling out of control, which could damage the host’s cells and tissues. ▪ C1-INH acts as a serine protease inhibitor ▪ Detaches C1r and C1s from C1q (Inhibits the recognition unit of the classical pathway). ▪ Inactivates MASP-2 (Inhibits the recognition unit of the lectin pathway) ▪ Hereditary angioedema (HAE) ▪ In this genetic condition, a deficiency or dysfunction in C1-INH leads to unchecked complement activation, causing episodes of severe swelling due to the overproduction of vasoactive peptides. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE FACTOR I ▪ Factor I is a serine protease that inactivates complement components C3b and C4b in the presence of: ▪ C4BP (C4-binding protein) ▪ CR1 (complement receptor 1) ▪ MCP (membrane cofactor protein) ▪ DAF (Decay-accelerating factor) ▪ This cleavage leads to the inactivation of the C3 convertase. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE DECAY ACCELERATING FACTOR (DAF) ▪ CD55 ▪ DAF is capable of dissociating both classical and alternative pathway C3 convertases. ▪ Displaces Bb and C2a from C3b and C4b, respectively ▪ It can bind to both C3b and C4b in a manner similar to CR1. ▪ It does not prevent initial binding of either C2 or Factor B to the cell but can rapidly dissociate both from their binding sites, thus preventing the assembly of an active C3 convertase. ▪ Protects host cells from bystander lysis SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE DECAY ACCELERATING FACTOR (DAF) ▪ CD55 ▪ DAF is capable of dissociating both classical and alternative pathway C3 convertases. ▪ Displaces Bb and C2a from C3b and C4b, respectively ▪ It can bind to both C3b and C4b in a manner similar to CR1. ▪ It does not prevent initial binding of either C2 or Factor B to the cell but can rapidly dissociate both from their binding sites, thus preventing the assembly of an active C3 convertase. ▪ Protects host cells from bystander lysis SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE FACTOR H ▪ Principal soluble regulator of the alternative pathway ▪ Mode of action: 1. Factor H (FH) competes with factor B (B) for binding to spontaneously (hydrolytically) activated C3b. 2. Factor H dissociates any C3bBb complexes that form on self-cell surfaces. 3. Factor H is a cofactor with factor I (FI), enabling cleavage of C3b. The resulting C3bi loses enzymatic activity but is still an opsonin. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE FACTOR H ▪ Principal soluble regulator of the alternative pathway ▪ Mode of action: 1. Factor H (FH) competes with factor B (B) for binding to spontaneously (hydrolytically) activated C3b. 2. Factor H dissociates any C3bBb complexes that form on self-cell surfaces. 3. Factor H is a cofactor with factor I (FI), enabling cleavage of C3b. The resulting C3bi loses enzymatic activity but is still an opsonin. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE FACTOR H ▪ Principal soluble regulator of the alternative pathway ▪ Mode of action: 1. Factor H (FH) competes with factor B (B) for binding to spontaneously (hydrolytically) activated C3b. 2. Factor H dissociates any C3bBb complexes that form on self-cell surfaces. 3. Factor H is a cofactor with factor I (FI), enabling cleavage of C3b. The resulting C3bi loses enzymatic activity but is still an opsonin. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE S-PROTEIN (VITRONECTIN) ▪ S protein acts by binding to the fluid- phase C5b-7 complex, preventing it from attaching to nearby cell membranes. ▪ Inhibits C9 polymerization. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE MEMBRANE INHIBITOR OF REACTIVE LYSIS (MIRL) ▪ CD59 ▪ It targets a later stage of MAC assembly. ▪ When the C5b-8 complex, having escaped S protein regulation, attempts to insert into the host cell membrane, MIRL binds to C8 and prevents the recruitment and polymerization of C9. ▪ This targeted inhibition ensures that even if the MAC assembles partially on a host cell, it cannot complete its lethal attack. SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY REGULATORS OF THE COMPLEMENT CASCADE SUMMARY ↑ SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY DISEASES ASSOCIATED WITH DEFICIENT COMPLEMENT COMPONENTS SUMMARY SAN PEDRO COLLEGE SCHOOL OF MEDICAL LABORATORY SCIENCE REFERENCES: ▪ Stevens, C. D., & Miller, L. E. (2016). Clinical Immunology and Serology: A Laboratory Perspetive. F.A. Davis. IMMUNOLOGY & SEROLOGY