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Flashcards in GI Host Defense Deck (29):
1

What are some first lines of defense in the GI system? (Immediate)

Epithelium: physical barrier, ion transport (diarrhea)
Physiologic: pH, mucus, microbiota, lysozyme, antimicrobial peptides
Complement

2

What are some second lines of defense in the GI system? (early)

Phagocytes --> inflammation
Macrophages --> inflammation
Granulocytes --> anti-parasitic
NK cells --> antiviral

3

What are some components of the adaptive immunity of the GI system?

T cells: helper T cells (CD4)
Cytotoxic T cells (CD8)

B cells: IgA, IgG, IgE, IgM

4

What are the different T cell types involved in the adaptive immunity of the GI system?

Th1: IFN --> inflammation
Th2: IL4 --> anti-parasitic
Th17: IL17 --> inflammation

5

What are some roles of commensals in the GI system?

1. Compete for resources with more virulent organisms
2. Produce their own antimicrobial peptides (AMPs)
3. Keep innate immune cells in an attentive state

6

What do defensins do?

Penetrate the lipid bilayer of bacteria and form pores

7

What are some examples of secretagogues?

VIP
Acetylcholine
Substance P
Prostaglandins & leukotrienes
Histamine
Serotonin

8

What are some examples of inhibitors?

Norepinephrine
Somatostatin

9

How can CF lead to intestinal obstruction?

Mutations in the gene for cAMP-responsive apical anion channel --> near absence of electrolyte secretion

10

How does TGF-beta lead to restitutive epithelium?

It is fibrogenic agent -- inhibits lymphocytes proliferation and also stimulates division, differentiation and migration of surrounding epithelial cells

11

What links the early innate responses with late adaptive immune response?

Dendritic cells

12

What cell types express TLRs?

Plasma membrane of epithelial cells, dendritic cells, macrophages, and PMNs

13

What PAMP do TLRs recognize?

Numerous bacterial, fungal and viral structures

14

What cell types express NLRs?

Cytoplasm of epithelial cells, macrophages, PMNs

15

What PAMPs do NLRs recognize?

Bacterial wall components (peptidoglycans)

16

What cells types express mannose receptors?

It is a membrane receptor on phagocytes that recognizes bacterial cell wall, carbohydrate and fungal wall glycans

17

What are some examples of soluble recognition receptors?

C-reactive protein - recognizes microbial cell wall components
Mannose-binding lectin - recognizes bacterial cell wall carbohydrates
Complement-C3 - recognizes microbial cell walls
IgM - recognizes bacterial cell walls

18

What is the function of TLRs?

Activate genes necessary for defense against the recognized bacterial, viral or fungal organism.

19

Which intestinal bacterial infections are minimally invasive?

Campylobacter
Clostridium
Candida
Cryptococcus

20

Which intestinal bacterial infections are invasive?

Listeria
Enteroinvasive E. coli

Opportunist: Clostridium, Shigella

21

Which intestinal bacterial infections are toxigenic??

Enterotoxigenic E. coli
Vibrio cholerae

(Clostridium)
(Shigella)

22

Alternative complement pathway

Cleave C3 protein binds bacterial surface

23

Classical complement pathway

Ab (IgM, IgG) binds to bacterial surface

24

Lectin complement pathway

Mannose binding lectin binds surface of bacteria

25

What are some GI viruses that can lead to disease?

Rotavirus
Norwalk
Enteroviruses

26

What are some intestinal parasites? How does our immune system respond to them?

Trematodes
Nematodes
Cestodes

*Too big to be phagocytes

27

What type of cell is important in defense against helminth parasites?

Granulocytes: eosinophils, basophils, mast cells
*Non-phagocytic --> they defend the host by releasing their granule contents into the extracellular space

28

How are granulocytes activated?

Ag-bound IgE binding cell surface FceRI
**So it depends on previous exposure to an Ag (sensitization)

29

What are some things that granulocytes release?

Vasoactive amines
Prostaglandins
Leukotrienes
Proteases
Cytokines