B-I Innate immunity and complement

Question 1

Types of barriers

Answer 1

Anatomical, mechanical, chemical, microbiological

Question 2

Describe the anatomical barrier

Answer 2

Prevents pathogen entry physically. Examples include the skin, epithelium in lungs, gut

Question 3

Describe the mechanical barrier

Answer 3

Also physically prevents entry by pathogens. Examples include tight junctions between cells, flow of air and fluid (mucus, tears) over the anatomical barrier

Question 4

Describe the chemical barrier

Answer 4

Breaks down or destroy pathogens. Low pH in the stomach, antimicrobial proteins and toxic chemicals

Question 5

Lysozyme

Answer 5

An antimicrobial glycosidase that breaks down a chemical bond in peptidoglycan in the bacterial cell wall. Produced by neutrophils

Question 6

Defensin

Answer 6

Peptide that is electrostatically attracted to bacterial membrane and form pores in them, destroying the cell

Question 7

How does the microbiota help with the immune system?

Answer 7

Fights for space with pathogenic bacteria, can kill them. Producing antimicrobial substances. Stimulates epithelial cells to produce antimicrobial substances as well

Question 8

Macrophage

Answer 8

Activated monocytes. Round nucleus with massive vacuoles. Does phagocytosis, activated bactericidal mechanisms, APC, produces cytokines

Question 9

What cytokines do macrophages produce?

Answer 9

IL-1β, TNF-α, IL-6, CXCLβ, IL-12

Question 10

Dendritic Cell - DC

Answer 10

Has long arms so it can present a lot of MHC Class II. Does antigen uptake in peripheral tissue, APC, cytokine production

Question 11

Neutrophil

Answer 11

Granulocyte. Vesicles. Does phagocytosis and activates bactericidal mechanisms

Question 12

Mast cell

Answer 12

Releases histamines

Question 13

Basophil

Answer 13

Granulocyte. Promotes allergic responses and is responsible for anti-parasitic immunity

Question 14

Eosinophil

Answer 14

Kills parasite coated with antibodies

Question 15

Natural Killer cell (NK cell)

Answer 15

Releases granules that induces apoptosis in virus infected and tumor cells. Has both activating and inhibitory receptors, activates when there’s an imbalance of receptors bound.

Question 16

Innate lymphoid cells (ILCs)

Answer 16

A class of lymphoid cells (which includes NK cells). Produces cytokinins?

Question 17

Pattern recognizing receptors (PRRs)

Answer 17

Sensors for immune cells to detect microbes. Expressed by epithelial cells also. Recognizes PAMPs and DAMPs.

Question 18

Toll-like receptors (TLRs)

Answer 18

Transmembrane receptors. Can detect both extracellular bacteria but also bacteria taken in by vesicles, and they sit in the membrane in the vesicle.

Question 19

NOD-like receptors (NLRs)

Answer 19

Not membrane bound, dimerize when they come in contact with ligand

Question 20

Inflammasome

Answer 20

Oligomerized NLRs that cleaves and activates caspase 1 which in turn cleaves gasdermin D, pro-IL-1β and pro-IL-18. Gasdermin D creates pore so that IL-1β and IL-18 can get out of the cell

Question 21

PAMPs

Answer 21

Conserved, microbe specific patterns

Question 22

DAMPs

Answer 22

Endogenous molecules from damaged or dying cells that should not be in the extracellular space. Ex. nuclear proteins

Question 23

Phagocytosis

Answer 23

Engulfment of large particles, energy dependent. Can be done by multiple immune cells such as macrophages, neutrophils

Question 24

Process of phagocytosis

Answer 24

PRRs bind and identify microbe. Enclose the particle in a vacuole inside the cell. This vacuole fuses with the lysosome, where the particle is killed with toxic compounds, pH, enzymes, etc

Question 25

What is the complement system?

Answer 25

Proteolytic enzymes that circulate through the blood. Can recognize certain classes of antibodies, surface proteins, or whole microbes, and causes a cascade amplification. Stimulates phagocytes, induces inflammation, and creates the MAC which is a pore that kills the bacteria

Question 26

What are the pathways of activation for the complement system?

Answer 26

Lectin, classical, alternative

Question 27

Lectin pathway

Answer 27

Activating proteins binds to carbohydrates on surface of microbes

Question 28

Classical pathway

Answer 28

Activating proteins interact with antibody bound to the surface of the microbe

Question 29

Alternative pathway

Answer 29

Activating protein will spontaneously hydrolyze and bind directly to the microbe(?)

Question 30

C3 convertase

Answer 30

Key part of the complement system. Cleaves C3 into C3a and C3b. Is made out of different components depending on which activating pathway was used.

Question 31

C3A

Answer 31

Soluble. With C5A it will recruit phagocytic cells and promote inflammation

Question 32

C3B

Answer 32

Stuck to surface of microbe. Will bind to C3 convertase to form C5 convertase. Furthermore, it can cause phagocytes to engulf the pathogen as it can bind to C3B receptors on them.

Question 33

C5 convertase

Answer 33

Cleaves C5 to C5a and C5b. Made out of different components depending on which pathways was used.

Question 34

C5a

Answer 34

Together with C3a to recruit phagocytic cells and promote inflammation. Stronger than C3a.

Question 35

C5b

Answer 35

Key to creating MAC pores that disrupts the cell membrane which kills the cell.