Immunology Lecture 7.

Question 1

What does activation of the complement cascade result in?

Answer 1

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

Question 2

What are the two most important functions of complement?

Answer 2

inflammation mediator and opsonization

Question 3

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

Answer 3

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

Question 4

What is the purpose of C3b?

Answer 4

tags bacterium for destruction

Question 5

What is the purpose of C3a?

Answer 5

recruits phagocytes

Question 6

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

Answer 6

C1-C4-C2a-C3b

Question 7

What does deposition of C3b lead to?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

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

Answer 9

ligand: C3b function: stimulate phagocytosis

Question 10

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

Answer 10

classical system

Question 11

What is the function of C5a?

Answer 11

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

Question 12

What is the lytic pathway?

Answer 12

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

Question 13

What is the importance of C3a and C5a?

Answer 13

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

Question 14

Why is inhibition of complement necessary?

Answer 14

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

Question 15

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

Answer 15

RBC because no nucleus

Question 16

What are inhibitors in the classical pathway?

Answer 16

C4-binding protein

Question 17

What are inhibitors in the alternative pathway?

Answer 17

factor H and factor I, DAF, MCP

Question 18

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

Answer 18

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

Question 19

What does deficiency in C3 cause?

Answer 19

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

Question 20

What does deficiency in C5-C9 cause?

Answer 20

susceptibility to neisseria

Question 21

What does deficiency in factor I cause?

Answer 21

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