Barrier Immunity of Gut

Question 1

TH1 cells secrete IFN-y which stimulates class switching to ?

Answer 1

IgG subtypes

Question 2

TGF-beta and retinoic acid seem to stimulate class switching to

Answer 2

IgA

Question 3

TH2 cells secrete IL4 and IL5 which stimulates class switching to

Answer 3

IgE

Question 4

what is the function of IgE

Answer 4

binds to cells with an Fc receptor for IgE triggering degranulation of granulocytes (eosinophils, basophils, mast cells)

Question 5

IgE is secreted as a ?

Answer 5

monomer

Question 6

IgA is predominantly found as a ? secreted into the ?

Answer 6

dimer
GI and respiratory tract mucous

Question 7

what is important function in developing tolerance within the mucosal immune system

Answer 7

IgA

Question 8

what are major types of innate lymphoid cells (ILCs)

Answer 8

• NK cells
• “resident” ILCs

Question 9

Type 1 ILCs secretes ?

Answer 9

secrete cytokines such as IFN-y and TNF-a -> “pushes” the barrier into a “Type 1” response and favours the development of Th1 cells

Question 10

Type 2 ILCs secretes?

Answer 10

secrete cytokines such as IL-4, IL-5, IL-9, IL-13  “pushes” the barrier into a “Type 2” response and favours the development of Th2 cells

Question 11

Type 3 ILCs secretes?

Answer 11

secrete IL-17, IFN-y -> effective against extracellular bacteria

Question 12

what are claudins in tight junctions?

Answer 12

trans-membrane proteins that can act as channels for small molecules (paracellular)

Question 13

what are occludin in tight junctions?

Answer 13

trans-membrane protein, function not clear

Question 14

what are Junctional adhesion molecules (JAM)?

Answer 14

Trans-membrane protein that may mediate permeability to larger molecules

Question 15

what are ZO-proteins in tight junctions?

Answer 15

Important in tight junction formation, interact with the cytoskeleton

Question 16

what are Peyer’s patches?

Answer 16

large collections of lymphoid nodules in the ileum

Question 17

what are Isolated lymphoid follicles (ILFs)?

Answer 17

MALT nodules without capsules, much smaller than peyer’s patches

Question 18

what does goblet cells do?

Answer 18

Secrete mucous, which presents a barrier to bacterial invasion

Question 19

what secretes anti-microbial peptides (AMPs) that prevent bacteria from getting “too close” to the epithelial lining

Answer 19

goblet cells

Question 20

what else secrete large quantities of AMPs?

Answer 20

paneth cells

Question 21

what are Very specialized cells present over the surface of Peyer patches and isolated lymphoid follicles (ILFs)

Answer 21

microfold cells

Question 22

what impairs bacterial mobility and makes it difficult for bacteria to penetrate the epithelial barrier

Answer 22

mucous in the lumen

Question 23

what is secreted mostly by Paneth cells, mainly toxic against gram (+)-ve bacteria but also seems to have some activity against gram (-)-ves

Answer 23

REG3

Question 24

what does “unshuffled” IgA mean

Answer 24

the antibody sequence has not undergone affinity maturation – is often broadly specific for a wide range of microbes

Question 25

what does "shuffled" IgA mean

Answer 25

the antibody sequence has undergone affinity maturation due to Th-B cell interactions

Question 26

IgA is secreted from plasma cells from 3 major sources:

Answer 26

- ILFS - Peyer's patches - Plasma cells in the mesenteric lymph nodes located around the abdominal aorta

Question 27

what induces IgA class switching in B-cells via TGF-beta, and CD40L/iCOS interactions – RA plays a role but is not secreted by follicular T cells

Answer 27

T-dependent – follicular T cells (Tfh)

Question 28

when activated, ILC3 cells secrete?

Answer 28

○ Secrete IL-22 & IL-17, which leads to increased production of AMPs by enterocytes and Paneth cells ○ Secrete factors that induce the full development of Peyer’s patches and ILFs and IgA production ○ Amplify the Th17 response in the gut

Question 29

Th17 cells can be induced to become either:

Answer 29

- Tfh cells - Treg cells

Question 30

what "messes with" our intestinal immune in a complex and multi-step way

Answer 30

Gluten

Question 31

what is a degradation product of gluten and is resistant to proteolytic degradation by pancreatic enzymes

Answer 31

alpha-gliadin

Question 32

what does gliadin bind to?

Answer 32

chemokine receptor CXCR3

Question 33

what does CXCR3 produce and release

Answer 33

zonulin

Question 34

What happens when zonulin bind to its receptor

Answer 34

disassembly of ZO proteins -> disassembly of tight junctions

Question 35

what is the adult presentation of celiac disease

Answer 35

- anemia, chronic diarrhea - bloating, fatigue - deficiencies in B12 and iron

Question 36

what is the pediatric presentation of celiac disease

Answer 36

○ Irritability, anorexia, chronic diarrhea, weight loss muscle wasting (malabsorption) ○ Some present with abdominal pain, nausea, vomiting, bloating, or constipation