Complement System Flashcards
Complement activation is regulated by a series of _____ that serves to protect host cells from accidental damage
proteins
2 major functions of the complement system
alters membrane of pathogens and cellular debris; enhance inflammatory response via release of anaphylatoxins that promote cell activation or migration to an inflammatory site
factors which block or inhibit activation of complement. Two general types—soluble and membrane bound
Complement inhibitors
a system of plasma proteins that can be activated directly by pathogens or indirectly by pathogen-bound antibody, leading to a cascade of reactions that occurs on the surface of pathogens and generates active components with various effector functions. system plays a crucial role in the innate defense against common pathogens. … It is now appreciated that it is a functional bridge between innate and adaptive immune responses that allows an integrated host defense to pathogenic challenges
Complement
directed migration of a cell or group of cell to a chemical gradient
Chemotaxis
Drug that is an antibody against activated C5b that is used to block complement lytic actions in human disease
Eculizumab
____ is composed of 6 identical subunits with globular. heads and long collagen-like tails; the heads can bind to the constant regions of immunoglobulin molecules or directly to the pathogen surface
C1q
Mannose-binding lectin forms a complex with ______ that resembles complement complex C1; these do much of the work in MBL pathway
serine proteases
is a structure typically formed on the surface of pathogen cell membranes as a result of the activation of the host’s complement system, and as such is one of the effector proteins of the immune system. forms transmembrane channels. These channels disrupt the cell membrane of target cells, leading to cell lysis and death.
Membrane attack complex (MAC)
complement fragments C3a, C4a, and C5a, which are produced by complement activation. act as cell activators with nanomolar affinity, exerting their functions through binding to specific receptors (C3aR and C5aR or C5L2 respectively).
Anaphylatoxin:
carbohydrate binding protein. Displays specificity for single or group of sugars.
Lectin
C5 convertase cleaves C5 into ____ which generates the _________ and _______ which is a potent pro-inflammatory mediator
C5b; Membrane attack complex and C5a
immune function triggered by complement system; by chemotactically attracting macrophages and neutrophils (anaphylatoxins C3a and C5a).
inflammation
C1 is a complex of what 3 components?
C1q, C1r, and C1s
type of white blood cell. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems and contains many granules rich in histamine and heparin (anticoagulant). Although best known for their role in allergy and anaphylaxis, play an important protective role as well, being intimately involved in wound healing, angiogenesis, immune tolerance, defense against pathogens, and blood–brain barrier function
Mast cell
Membrane protein that displaces Bb from C3b and C2a from C4b
Decay-accelerating factor (DAF)
Which complement pathway is continuously activated at a low level as a result of spontaneous C3 hydrolysis due to the breakdown of the internal thioester bond; doesn’t rely on pathogen-binding antibodies like the other pathways
alternative pathway
Increased vascular permeability is carried out by
C3a and C5a
______ dissociates C3 convertases at human cell surfaces and makes them susceptible to cleavage by factor 1
MCP
Which complement pathway is triggered by C1-complex?
classic pathway
immune function triggered by complement system; by opsonizing antigens. C3b has most important opsonizing activity
Phagocytosis
Which pathway is homologous to classical pathway but uses opsonins, mannose-binding lectin, and ficolin instead of C1q
mannose-Binding lectin pathway
increase in efficiency of antibody mediated phagocytosis by binding of antibody to bacteria and then recognition of antibody-coated particle by receptor on phagocyte cell.
Opsonization
a white cell in blood which is enriched in heparin and vasodilator histame
Basophil
The component of the vertebrate immune system involving lymphocytes (B cells and T cells) containing a small number of genetically encoded proteins that combine to produce an enormous variety of proteins capable of recognizing and deactivating specific antigens
adaptive immune system
acute allergic reaction to substance to which host is hypersensitive
Anaphylaxis
target dead cells/ pathogens and clear them out of the body
complement system
Smooth muscle contraction is carried out by
C3a and C5a
Most common functional defect in atypical hemolytic uraemic syndrome and age-related macular degeneration is reduced cofactor activity for _____
C3b
ingestion of bacteria or other material by phagocyte cell.
Phagocytosis:
bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane
Gram negative bacteria
starts opsonization
C3b
is a G protein-coupled receptor for C5a. It functions as a complement receptor. modulates inflammatory responses, obesity, development and cancers.
C5aR
is a part of the immune system that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen’s cell membrane; part of the innate immune system
complement system
component of alternative pathway that initiates assembly of the membrane-attack system
C5b
Degranulation of mast cells are carried out by
C3a, C5a play a role in degranulation in anaphylaxis
C4b2a is ________; it will lead to the generation of _____
C3 convertase; C5 convertase
immune function triggered by complement system; by rupturing cell wall of bacteria
membrane attack
Complement receptor type 1 also known as C3b/C4b receptor or CD35 is a protein that in humans is encoded by the CR1 gene. Functions in opsinizatio of immune complexes and antibody tagged bacteria
C3b receptor (CR1)
3 pathways of complement system
alternative pathway (C3), classical pathway (Abs), and lectin pathway (lectins bind to carbs)
genetic diseases caused by absence of particular receptors which are used to recognize foreign cells and remove them from blood stream.
Immunodeficiency syndromes
is involved in the complement system. It binds to iC3b (inactive derivative of C3b), C3dg, or C3d.]B cells have CR2 receptors on their surfaces, allowing the complement system to play a role in B-cell activation and maturation
C3d receptor ( CR2)
coating invading organisms with proteins that the body will recognize and body will trigger phagocytosing molecules
opsonization
Cleaves C4 and C2
C1s
a local response to cellular injury that is marked by capillary dilatation, leukocytic infiltration, redness, heat, and pain and that serves as a mechanism initiating the elimination of noxious agents and of damaged tissue
Inflammation
component of the immune system in animals that is genetically determined and is nonspecific
innate immune system
Diagnostic tests for complement activity
total complement activity test
