Lecture 20: Immunity to Microbes

Question 1

What do acute phase proteins CRP and SAP do?

Answer 1

Bind C1q on bacteria and activate complement

Question 2

What role do C3a and C5a have in extracellular infections

Answer 2

Bind receptors on mast cells and activate them to release histamine

Question 3

What activates the endothelium and neutrophils in extracellular infection

Answer 3

Cytokines released from mast cells along with bacterial derived molecules (endotoxins)

Question 4

What are two examples of potent neutrophil chemoattractants

Answer 4

C3a and C5a

Question 5

Role of immature vs mature DCs in extracellular infections

Answer 5

Immature DCs engulf bacteria via PRRs, mature DCs migrate to local lymph nodes

Question 6

What adhesion molecules are responsible for the adhesive interaction b/w lymphocytes and HEVs

Answer 6

L-selectin on lymphocytes

PNAds on HEVs

Question 7

Where do activated Th cells interact with B cells to promote affinity maturation/Ig class switching

Answer 7

Germinal centers

Question 8

Endotoxins vs exotoxins

Answer 8

Endotoxin- Component of bacterial cell wall

Exotoxin- Secreted by bacteria

Question 9

Principal mechanisms of innate immunity to extracellular bacteria are

Answer 9

Complement activation
Phagocytosis
Inflammation

Question 10

Peptidoglycans (Gram+) and LPS (gram-) bacteria activate which pathways

Answer 10

Alternative and classical pathways

Question 11

What causes the cleavage of C3b and C4b that prevents them from forming active convertases

Answer 11

Factor I

Question 12

What are the cofactors for Factor I

Answer 12

MCP
CR1
Factor H
C4BP

Question 13

What proteins inhibit assembly of C3 convertase in classical pathway

Answer 13

DAF
CR1
C4BP

Question 14

What proteins inhibit assembly of C3 convertase in alternate pathway

Answer 14

DAF
CR1
Factor H

Question 15

What is the classical C3 convertase

Answer 15

C2aC4b

Question 16

What is the alternative C3 convertase

Answer 16

C3bBb

Question 17

What can inhibit the assembly of the MAC

Answer 17

MAC-Inhibitory protein CD59

Question 18

Encapsulated bacteria rich in TI polysaccharide Ags are primarily eliminated by

Answer 18

Ab-mediated immunity

Question 19

What is the role of Th17 cells when activated by extracellular Ags, and what happens if there is a genetic defect in the Th17 cells

Answer 19

Promote local inflammation and recruit neutrophils and monocytes to the area
-Increased susceptibility to bacterial/fungal infections, with formation of multiple skin abscesses

Question 20

What is the role of Th1 cells when activated by extracellular Ag

Answer 20

Produce IFN-y which activates macrophages

May also stimulate production of IgG Abs

Question 21

What are the principal injurious consequences of host responses to EC bacteria

Answer 21

Inflammation and septic shock

Question 22

What causes the early phase of septic shock

Answer 22

Cytokines produced by macrophages

Question 23

Macrophages secrete TNF-a which does what

Answer 23

Upregulates Tissue Factor TF and nitric oxide synthase (iNOS)

Question 24

What is the role of IL-18 secreted by macrophages

Answer 24

Induces IFN-y which activates more macrophages

Question 25

What cytokine is a global suppressor of macrophage function

Answer 25

IL-10

Question 26

What are local effects of IFN-a in viral infections

Answer 26

Inhibition of viral gene replication Up-regulation of MHC class I molecules Activate NK cells early in infection

Question 27

What is the major mechanism used by bacteria to evade humoral immunity

Answer 27

Variation of surface Ags

Question 28

What activates NK cells at later stages of viral infections

Answer 28

IFN-y and IL-2 produced by Th1 cells

Question 29

What are Langerhans cells

Answer 29

Tissue DCs in the skin which transport Ag to local lymph nodes

Question 30

What molecules locally produced by macrophages and T cells have systemic effects of fever

Answer 30

IL-1 and TNF-a

Question 31

Naïve B cells acquire viral Ags through

Answer 31

Attachment to surface IgM or IgD

Question 32

Th1 cells recruit and stimulate virus specific CTLs by providing ____ for _____

Answer 32

IL-2 for proliferation of CD8+ T cells

Question 33

What are the key attributes of effector Th cells and CTLs in viral infections

Answer 33

Virus specific TCRs Upregulation of adhesion molecule LFA-1 Upregulation of production of cytokines

Question 34

After death, viral secreted proteins are removed/neutralized by

Answer 34

Ab in the form of immune complex | Ab may guide Fc receptor-expressing NK cells

Question 35

When pathogenic bacteria are resisting degradation by phagocytic cells, this can be overrun by NK cells producing ____. Which cells release which cytokines to stimulate the NK cells to do this

Answer 35

Dendritic cells and macrophages produce IL-12 and IL-15 to activate NK cells to produce IFN-y which in turn promotes killing of phagocytized bacteria by macrophage

Question 36

Endogenous pathway of Ag presentation

Answer 36

Proteins from IC pathogens such as viruses are degraded by proteasome and the peptides are shuttled into the ER by TAP proteins and presented in MHC class I molecules

Question 37

Exogenous pathway of Ag presentation

Answer 37

``` Extracellular pathogens are engulfed by phagosomes, in the phagosome, the peptides are loaded onto MHC class II molecules which activate Th cells to stimulate Ab production (some peptides from exogenous pathway can be cross presented on MHC class I molecules) ```

Question 38

Fungi are recognized by what receptors

Answer 38

PRRs

Question 39

The detection of _____ by _____ is important for fungal infection

Answer 39

B-glucan by dectin 1

Question 40

What cytokines activate Th1, Th2 and Th17 cells

Answer 40

``` Th1 = IL-12 Th2 = IL-4, IL-5 Th17 = TGF-b, IL-6 ```

Question 41

In general, in fungal infections, Th1 responses do what, while Th2 responses do what

Answer 41

Th1 responses are required for clearance, while Th2 responses usually result in susceptibility to infection

Question 42

What is Dectin-1 role in fungal infections

Answer 42

Expressed on Macrophages. Binds and internalizes B-glucans and mediates activation of NF-kB and subsequent secretion of proinflammatory cytokines and ROS