GI - immunology

Question 1

what is the name of the lymph nodes found in the gut

Answer 1

peyer’s patches

Question 2

what is the function of the ruffled membranes of M cells of payer’s patches

Answer 2

antigen sampling and absorption - endocytosis and phagocytosis

Question 3

true/false

dendritic cells project themselves across epithelial membrane of gut to sample antigen in gut lumen

Answer 3

true

Question 4

where are cytotoxic T cells (CD8) found in gut

Answer 4

epithelium (intraepithelial lymphocytes)

Question 5

where are helper T cells (CD4) found in gut

Answer 5

lamina propria of gut cells

Question 6

how are T cells in lamina propria activated

Answer 6

dendritic cells capture antigen at membrane, migrate to lymph nodes and present to T cells

Question 7

what is MA

Answer 7

molecular address signal - binds to effector T cells which need to return to that area in the gut

Question 8

what is chemokines role in gut immunity

Answer 8

direct migration of T cells through gut epithelium

Question 9

why do HIV patients have mucosal immune dysfunction

Answer 9

loss of 70% of CD4+ T cells (helper/memory) in gut

Question 10

where are IgA cells found in gut

Answer 10

lamina propria

Question 11

how does IgA enter the epithelium from lamina propria

how does it enter gut lumen

Answer 11

endocytosis

exocytosis - while doing so can transport pathogens back to gut lumen

Question 12

what is the purpose of the secretory component

Answer 12

allows IgA to persist in gut lumen for a awhile without being digested by proteolytic enzymes

Question 13

how does IgA neutralise antigens

Answer 13

internalising them within a vesicle

Question 14

what is the function of IgA

Answer 14

stops toxins and pathogens binding to gut epithelium

Question 15

give 4 examples of when the mucosal immune system is dysregulated

Answer 15

primary immunodeficiency
allergy
coeliac disease
IBD

Question 16

where do intraepithelial cells kill infected epithelial cells

Answer 16

basolateral side

Question 17

what kind of immunodeficiency is HIV

Answer 17

acquired

Question 18

what is XLA

Answer 18

X linked agammaglobulinaemia
no B cells
no IgG
recurrent infection
tx: immunoglobulin injections

Question 19

what is a phagocyte respiratory burst

Answer 19

phagocytes produce reaction oxygen species (superoxide) to kill pathogens

Question 20

what is chronic granulomatous disease

Answer 20

primary immunodeficiency

failure of phagocytes to produce superoxides for respiratory bursts

Question 21

what is SCID

Answer 21

no B or T cells

constant pulmonary and GI infection

Question 22

how is an allergy self-perpetuating

Answer 22

activated mast cells produce IL4 which stimulates B cells to produce more IgE

Question 23

what genes trigger coeliac

Answer 23

HLA-DQ2
HLA-DQ8
(responsible for protein that activates T cell response)

Question 24

what immune cells mediate coeliac

Answer 24

T cells

Question 25

what occurs in coeliac

Answer 25

gluten specific T cells produce interferon gamma which triggers intraepithelial lymphocytes (CD8) to kill epithelial cells

Question 26

what is the presentation of coeliac

Answer 26

``` abdominal pain bloating diarrhoea / steatorrhoea weight loss anaemia ```

Question 27

what is seen in coeliac

Answer 27

flattened epithelium | villi atrophy

Question 28

what is the gold standard Dx for coeliac

Answer 28

duodenal biopsy after positive tTG-IgA test | biopsy not in children

Question 29

what is tTG

Answer 29

tissue transglutaminase enzyme that modulates gluten by forming a complex with it when it enters the gut the more gluten you eat the more tTG presented to B cells - more epithelial damage done

Question 30

does the large intestine have villi

Answer 30

no just crypts

Question 31

does the small intestine have villi

Answer 31

yes | villi and crypts

Question 32

do both the small and large intestine have goblet cells

Answer 32

yes

Question 33

where are paneth cells found | what do they do

Answer 33

small intestine | secrete defensives - antimicrobial peptide

Question 34

where are peyer's patches found

Answer 34

small intestine

Question 35

where does antigen capture and activation occur in gut

Answer 35

mediated by dendritic cells | takes place in payer's patches and across epithelium

Question 36

what are M cells

Answer 36

part of epithelium covering Peyer's patches

Question 37

what are CCR7 and L-selectin

Answer 37

homing receptors which mediate T cell transport into payer's patches

Question 38

how do T cells become activated and reach the thoracic duct

Answer 38

activated by antigen bound dendritic cells lose CCR7 so can no longer circulate drain via mesenteric lymph nodes into thoracic duct

Question 39

what is the function of a4-B7 integrin on T cell and MAdCAM-1 on endothelium

Answer 39

receptors aiding transport of effector immune cell out of gut

Question 40

what Ig is most involved in humoral intestinal immune response

Answer 40

IgA