Immunology Lecture 7. Flashcards Preview

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Flashcards in Immunology Lecture 7. Deck (21):

What does activation of the complement cascade result in?

cell lysis, increased phagocytosis, increased vascular permeability, enhanced leukocyte chemotaxis, and functional stimulation of macrophages


What are the two most important functions of complement?

inflammation mediator and opsonization


What is the common end result of the classical and alternative pathways?

cleavage of C3 leading to the activation of a common sequence of events leading to cell lysis - c3b is left on surface of bacteria


What is the purpose of C3b?

tags bacterium for destruction


What is the purpose of C3a?

recruits phagocytes


What is the sequence of C’s in the classical pathway?



What does deposition of C3b lead to?

binding to complement receptors (opsonization and clearance of immune complexes) *promote phagocytosis


What are the functions and ligands of complement receptor 1 (CR1)

ligands: c3b and c4b function: promotes C3b and C4b decay, stimulate phagocytosis, erythrocyte transport of immune complexes *CR1 on macrophage will bind C3b on bacterium*, immune complexes can be carried by erythrocytes to the spleen where they are cleared out


What are the functions and ligands of complement receptor 3 and 4 (CR3 and CR4)

ligand: C3b function: stimulate phagocytosis


Which system is important for clearing immune complexes out of the blood?

classical system


What is the function of C5a?

important chemotactic factor - attracts most importantly neutrophils, also monocytes, lymphocytes


What is the lytic pathway?

C5, C6, C7, C8, C9 making pore for the destruction of Neisseria


What is the importance of C3a and C5a?

anaphylatoxins - histamine release for mast cells and increase vascular permeability (leaky) - C5a will draw monocytes and neutrophils


Why is inhibition of complement necessary?

Otherwise there would always be activation - on human cells so those cells are not destroyed - bacteria cells do not have inhibitors


Which cell is an exception to all human cells have inhibitors to complement?

RBC because no nucleus


What are inhibitors in the classical pathway?

C4-binding protein


What are inhibitors in the alternative pathway?

factor H and factor I, DAF, MCP


What does a deficiency in C1, C2, C4 cause?

immune-complex disease - not an increased rate of bacterial infections - these components lead to the enhanced uptake of solubilization of immune complexes resulting in the clearance of complexes


What does deficiency in C3 cause?

susceptibility to encapsulated bacteria (the ones without a capsule are easily eaten by phagocytes)


What does deficiency in C5-C9 cause?

susceptibility to neisseria


What does deficiency in factor I cause?

similar effects to deficiency of C3 because it is an inhibitor/cleaves C3. too much C3 binding, you use up all your C3