Immunology of the GI tract

Question 1

in which part of the GI tract are lymphocytes and plasma cells located?

Answer 1

epithelia and lamina propria

Question 2

the epithelia and lamina propria contain what immunological cells?

Answer 2

lymphocytes and plasma cells

Question 3

what is the most abundant Ig in the body?

Answer 3

IgA

Question 4

what is the big difference between mucosal immunity and normal immunity in terms of duration?

Answer 4

mucosal immunity does not last as long

Question 5

is there immune induction at effector cell sites? what are these sites?

Answer 5

no

lymphocytes in epithelia and lamina propria

Question 6

what GALT is important in promoting IgA production and CTL responses?

Answer 6

Peyer’s patches

Question 7

in which layer of the GI tract are Peyer’s patches located?

Answer 7

lamina propria

Question 8

where are M cells found? what is their role?

Answer 8

dome epithelium of Peyer’s patches

transfer antigens from gut lumen to lymphoid tissue, which are then presented to T helper cells by APCs

Question 9

M cells interact directly with which immune cells?

Answer 9

APCs

Question 10

Peyer’s patches are covered by epithelium consisting of what special cell type?

Answer 10

M cells

Question 11

what is the morphology of M cells?

Answer 11

ruffled, micro-folded membranes

Question 12

which microbes exploit M cells to get into gut wall?

Answer 12

salmonella, yersinia, listeria, shigella

Question 13

salmonella, yersinia, listeria, and shigella invade the gut wall through what mechanism?

Answer 13

bacterial proteins bind cellular receptors to induce uptake

phagocytosis and macropinocytosis via M cells

Question 14

intraepithelial lymphocytes are composed primarily of what immune cell?

Answer 14

CD8 T cells

Question 15

cells in the lamina propria are composed primarily of what immune cell?

Answer 15

CD4 T cells

Question 16

pre-plasma cells leave peyer’s patches via what channels?

Answer 16

lymphatic capillaries

Question 17

how do pre-plasma cells get to the lamina propria after leaving the peyer’s patches?

Answer 17

migrate via mesenteric lymph channels and thoracic duct

Question 18

what molecules play a role in the homing of pre-plasma cells to the lamina propria?

Answer 18

addressins

Question 19

how does IgA get to the mucosal surface?

Answer 19

binds to poly-Ig receptors and transported across cell and delivered to mucosal surface

Question 20

which IgA is dimeric? which is monomeric?

Answer 20

dimeric - mucosal

monomeric - serum

Question 21

how does IgA1 differ from IgA2?

Answer 21

IgA1 can fix complement via the alternative pathway

Question 22

how does IgA prevent binding of microbes to epithelia and facilitate expulsion?

Answer 22

opsonize small pathogens for phagocytosis

eosinophil degranulation for parasites - eosinophils have receptors for IgA

Question 23

what subtype of T cells make up a significant % of epithelia-associated T cells in the GI tract?

Answer 23

gamma delta

Question 24

what are the antigens for gamma delta T cells in the GI tract?

Answer 24

heat shock proteins, nucleotides, phospholipids

Question 25

what comprises secretory component?

Answer 25

a piece of a poly-Ig receptor

Question 26

what is the role of secretory component?

Answer 26

protects IgA from being broken down by proteolytic enzymes

Question 27

what supplies the secretory component?

Answer 27

mucosal cell itself

Question 28

where are mast cells located?

Answer 28

deep to epithelia that is exposed to environment

Question 29

what is the normal immune function of mast cells?

Answer 29

IgE mediated defense against parasites

Question 30

what is oral tolerance?

Answer 30

immune system is told to not respond to certain antigens a way to keep immune system's hands off of things you eat in order to avoid an undesirable immune response

Question 31

what occurs following high dose of oral antigen?

Answer 31

clonal deletion of antigen-specific lymphocytes (they die)

Question 32

what occurs following low dose of oral antigen?

Answer 32

clonal anergy (unresponsiveness) and regulatory T cells suppress immune responses regulatory T cells developed in GALT can migrate systemically

Question 33

what is the most common immunodeficiency in humans?

Answer 33

selective IgA deficiency

Question 34

selective IgA deficiency is associated with increased risk of what condition?

Answer 34

autoimmune disease

Question 35

reactions to food proteins are usually the result of what Ig?

Answer 35

IgE

Question 36

what is the response of intraepithelial lymphocytes following gluten sensitive enteropathy?

Answer 36

10x-15x increase in T cell reaction

Question 37

what is the result in the lamina propria following gluten sensitive enteropathy?

Answer 37

increase in TCR bearing CD4 and CD8 T cells

Question 38

untreated or partially treated gluten sensitivity enteropathy can lead to what conditions?

Answer 38

GI lymphoma, carcinoma

Question 39

crohn's disease

Answer 39

inflammatory and granulomatous lesions commonly involving terminal ileum and ascending colon

Question 40

what is the antibody therapy for crohn's disease?

Answer 40

infliximab

Question 41

what molecule plays a large role in crohn's disease?

Answer 41

TNFa

Question 42

how does ulcerative colitis begin? secondary?

Answer 42

diffuse lymphocyte rich infiltrate granulocytic inflammatory cells during abscess formation

Question 43

how does crohn's disease begin?

Answer 43

classic macrophage containing granulomatous lesions

Question 44

what is the most common cause of pernicious anemia? what is the result?

Answer 44

autoantibodies against IF B12 cannot be transported into circulation