Ch2 Innate Immunity: the Immediate Response to Infection

Question 1

complement system what is it and end goal

Answer 1

enzymatic (protease) cascade to label pathogens for destruction

Question 2

what is the compliment system made of

Answer 2

soluble compliment proteins-liver
soluble compliment control proteins
cell surface receptors on immune cells

Question 3

what is the outcome of compliment system

Answer 3

coat pathogen (opsonization)

Question 4

compliment fixation

Answer 4

c3 is cleaved into c3a-Chemoattractant
anaphylatoxins sounds the alarm and c3b-opsonizes pathogen complement fixation tags for identification and destruction

Question 5

what are the 3 pathways of compliment system and their order

Answer 5

1. Alternative Pathway is first to activate during infection; innate immunity.
2. Lectin Pathway is second to activate during an infection; innate immunity.
3. Classical Pathway is last to activate during an infection; innate and adaptive immunity

Question 6

how does C3 initiate the alternative pathway?

Answer 6

C3 hydrolyzes to iC3. Factor B is attracted to iC3 and binds to it. Factor D comes in and cleaves factor b into Bb and Ba. Ba is released and Bb stays on the iC3 making iC3Bb (soluble C3 convertase). ic3b cleaves C3 inta C3b and C3a. C3b binds to the pathogen

Question 7

how does C3b multiply on the pathogen surface?

Answer 7

factor B binds to C3b and factor D comes and cleaves it. It turned into C3bBb(insoluble) and Ba. C3bBb keeps cleaving C3 into C3b and C3a.

Question 8

what does Properdin do?

Answer 8

stabalizes the C3 convertase (C3bBb) on the pathogen surface. This is so it can keep making C3b to bond and fire up the immune system.

Question 9

what does factor H do?

Answer 9

innactivates C3b. it binds to C3b and changes its conformation. Factor i comes in and cleaves iC3b into an inactive form. Now iC3b cant bind b.

Question 10

DAF do to C3 convertase?

Answer 10

Decay accelerating factor binds to C3b and dislodges Bb when it tried to bind to C3b.

Question 11

what does MCP do to c3 convertase?

Answer 11

membrane cofactor protein (MCP) binds to C3b and dislodges Bb. this allows factor I to cleave iC3b and disrupts C3 convertase.

Question 12

What is the first effector cell to to encounter pathogens

Answer 12

macrophages

Question 13

how to macrophages swallow pathogens?

Answer 13

Macrophages are professional APC tissues that express many cell surface receptors. CR1 (compliment receptor 1) binds C3b on the pathogen. The macrophage endocytosises the pathogen the macrophage membranes fuse together to create the phagosome. Lysosomes fuse with the phagosome to form a phagolyosome.

Question 14

What other complement receptors bind to iC3b?

Answer 14

CR3 and CR4 (integrins) they have the same effect as CR1

Question 15

What are terminal complement components

Answer 15

C5-C9

Question 16

What are C5-C9 and what do they do?

Answer 16

they are terminal compliment components. They are used to form MAC (membrane attack complexes) which create holes in the membrane.

Question 17

how is C5 activated

Answer 17

C5 is similar to C3 but no thioester bond and different function. It is activated by alternative pathway C5 convertase: C3b2Bb. This creates C5a and C5b.

Question 18

How are Mac complexes formed

Answer 18

C5b binds C6 to make C5b6. C5b6 binds C7 which exposes a hydrophobic site for the pathogen to attach. C5b67 binds C8 which induces the polymerization of C9 molecules. 18 of the C9 molecules come together to form the MAC pore.

Question 19

How is the pore stopped from forming on the human cell?

Answer 19

CD59 binds to C5b678 complex. This prevents the recruitment of C9 to form the pore.

Question 20

Factors that prevent MAC pores from forming on the human cell?

Answer 20

Factor J, Protein S and clusterin- prevent the association of C5b, C6, C7

HRF (Homologous restriction factor) and C59 (protectin)- prevent polymerization of C9

Question 21

C3a and C5a are….?

Answer 21

Anaphylatoxins= mast cells and basophils

Chemoattractant= monocytes and neutrophils

Question 22

What are protease inhibitors?

Answer 22

Plasma proteins. The Alpha macroglobulin trick the protease with a bait region and engulf it. Macrophages then work to kill the protease.

Question 23

How do alpha macroglibulins trap proteases?

Answer 23

The alpha macroglobulin with a C3 like thoeister bond has a bait region that the protease interacts with. once the protease is baited it is covalently bonded with the alpha macroglobulin and the conformational shape changes. This causes the macroglobulin to engulf the protease and the macrophages then kill it.

Question 24

what are defensins and what are the 2 sub groups

Answer 24

defensins are a large family of anti microbial proteins. They are divided into 2 classes alpha defensin and beta defensin.

Question 25

What do defensins do?

Answer 25

disrupt the 3D structure of toxins ; anti-chaperones
create pores in the pathogen’s plasma membranes

Question 26

what is alpha defensin?

Answer 26

α defensins: myeloid and enteric [gut] defensins
❖ 4 are found in neutrophil granules
❖ HD5: human defensin 5 found in Paneth cells: small intestines ❖ HD6: human defensin 6 found in Paneth cells: small intestines.