Lecture 14: Specialized Immunity at the GI epithelial barriers Flashcards Preview

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Flashcards in Lecture 14: Specialized Immunity at the GI epithelial barriers Deck (25):
1

Patients with severly reduced C3 levels tend to have 

increased number of severe bacterial infections 

2

The membrane IgM and IgD on the surface of 

are identical except for their CH chains 

3

The ____ contains blood and lymphatic vessels, and mucosa-associated lymphoid tissues 

Lamina propria 

4

Specialized ______ cells deliver Ags across the epithelial barrier of the gut directly to subepithelial DCs that  then present Ag locally in adjacent mucosal T-cell areas

Microfold (M) cells 

5

which has a larger tolerance to bacteria the small or large intestine

 Large intestine (makes sense becaue it has more commensals)

6

Epithelial cells produce anti-microbial peptides _____

defensins 

7

Most immune responses are induced by PRRs but, instead, these responses can be ______ in the gut

Anti-inflammatory actions 

8

Physical/chemical barrier of the gut is formed by _____, which prevent microbes from contacting epithelial cells 

Mucins

9

Mucins inclued secred and cell surface _____

glycoproteins

10

The secreted mucins form what two layers of gel

  • outer less-dense layer that is normally colonized by bacteria
  • a denser inner layer that is bacteria-free
  • (note both layers contain anti-microbial substances are produced by the epithelial cells aka produced Defensins)

11

The apical surface of GI epithelial cells is coated with membrane-bound mucin proteins called the ____

glycocalyx

12

Mucins are replaced by newly synthesized molecules every ____ to ____ hours 

6-12 hours

13

What cytokines can increase mucin production 

  • IL-1
  • IL-4
  • IL-6
  • IL-9
  • TNF
  • IFNalpha
  • elastase (from neutrophils) 
  • microbial adhesive proteins 
  • (note that these can not only icrease production but can alter mucins glycosylation which are thought to increase barrier function against pathogens)

14

____ and ____ cells constitutively produce defensins to provide innate protection against luminal bacteria

Epithelial and Paneth cells 

15

Are encapsulated bacteria more resistant to defensins

yes

16

In the small bowel, the major defensins are the _____ produced by paneth cells 

Alpha-defensins

17

The ____ defensins are produced by epithelial cells in the colon

Beta-defensins

18

Defects in defensin production by epithelial cells is linked to ____ disease

Crohn's disease, a chronic inflammatory disease that can involve the entire GI tract

19

Commensal bacteria may express lipopolysaccharide, peptidoglycans, CpG DNA, and flagellin. Thus there are stringent control mechanisms to limit TLR-induced proinflammatory responses to commensal bacteria. Such as 

  • TLR signaling increases barrier function but NOT inflammation 
  • TLR5, which recognizes bacterial Flagellins, is exclusively expressed on the basolateral surface and thus it will be accessible only to bacteria that have invaded through the barrier 
  • The NOD-like receptors for flagellins are expressed in the cytosol of intesstinal epithelial cells
    • NOD-like receptors will activate inflammatory responses ony when pathogenic bacteria or their products gain access to the cytosol 

20

The dominant protective cell-mediated immune response of the gut consists of _____ cells

Th17

21

A major mechanism for controlling responses in the gut is the activation of 

Treg cells

22

The ___ cells are specialized intestinal epithelial cells found in the small bowel epithelium overlying the Peyer's patches and lymphoid follicles in the lamina propria

M cells 

23

In the Peyer's patches and mesenteric LNs, DCs convert dietary Vitamin A into ____ (induced by thymic stromal lymphopoietin, TSLP)

Retinoic acid

24

When Naive B or T cells are activated by Ag in the Peyer's patches and mesenteric LNs, they are exposed to Retinoic Acid that induces the expression of ____ and ___. Which leads to 

  • chemokine receptor CCR9 and the integrin Alpha4beta7 on the effecotr B and T cells 
  • The effector lyphocytes enter the circulation and home back into the gut lamina properia because the chemokine CCL25 (the ligand for CCR9) and the adhesion molecule MadCam (the ligand for Alpha4beta7) are dispayed on lamina propria endothelial cells 

25