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Gastrointestinal > Immunity of the GI tract > Flashcards

Immunity of the GI tract Flashcards

1
Q

True or false: the GI mucosal surface is colonized by bacteria

A

True

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2
Q

What is the most abundant isotype of Ig in the body?

A

IgA

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3
Q

What is the difference between the mucosal antibody response vs serum antibody response?

A

Memory is much shorter –month to years as opposed to decades

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4
Q

What is the response of lymphocytes that reside within the epithelium and lamina propria of the intestinal mucosa?

A

No immune induction

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5
Q

What are the two primary lymphoid tissues?

A

Thymus

Bone marrow

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6
Q

What are secondary lymphoid tissue?

A

LN

Spleen

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7
Q

What are tertiary lymphoid tissue?

A

Any place in the body that becomes infected

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8
Q

True or false: you can get both T and B cell response in the gut mucosa

A

True

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9
Q

Where in the gut do most bacteria reside?

A

Colon + ileum

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10
Q

What is GALT? What parts of the GI tract are included in this?

A

Gut associated lymphoid tissues

Peyer’s patches
Appendix
Lymphoid aggregates

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11
Q

What is the histological makeup of GALT sites?

A

Distinct B cell follicles and T cell areas

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12
Q

What layer of the GI tract houses the lamina propria? What is this area’s importance?

A

Lamina propria

Promoting IgA and CTL responses

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13
Q

What are M cells in the GI tract?

A

Microfold cells in Peyer’s patches that constantly sample antigens from their environment

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14
Q

Where are APCs housed in the GI tract mucosa?

A

T cell areas

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15
Q

True or false: M cells do not physically interact with underlying APCs, to stimulate them

A

False–the do physically stimulate them

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16
Q

What are the bacteria that can bind to the M cells in Peyer’s patches and gain entry into the cell?

A

Salmonella
Yersinia
Listeria
Shigella

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17
Q

What are the two mechanisms of bacterial uptake via M cells?

A

Phagocytosis and macropinocytosis

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18
Q

What happens when Shigella enters the M cells?

A

Busts out of the vesicle it was contained in, and shoots around into neighboring cells

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19
Q

What are intraepithelial lymphocytes?

A

Primarily T lymphocytes that are embedded in the GI epithelium, and are waiting for the same antigen to come back and kill it (they’re already primed)

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20
Q

What are alpha-beta T cells?

A

Standard T cells

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21
Q

What is the role of the mast cells in lamina propria?

A

Allow for hypersensitivity reactions and reactions against parasites (IgE mediated)

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22
Q

What is the role of Th cells?

A

Get the info from the APCs and stimulate antigen specific B cells to form germinal centers

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23
Q

What happens to the pre plasma cells when they leave the Peyer’s patch through efferent lymphatic channels?

A

Migrate via mesenteric lymph channels to the bloodstream via the thoracic duct to go home to the lamina propria

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24
Q

What are the proteins that play a role in the homing mechanism for pre plasma cells that are stimulated in the GI tract?

A

Addressins

25
Q

Where are fully matured plasma cells located in the GI tract (which layer)? What antibody do they secrete?

A

Lamina propria

IgA

26
Q

What is the receptor that binds IgA that plasma cells produce to translocate it through the epithelial cells?

A

Poly-Ig-receptor

27
Q

What is the role of the secretory component of the poly-Ig receptor that is broken off when IgA translocates through the epithelial cell?

A

Prevent degradation of IgA via the proteolytic enzymes that are in abundance in the gut

28
Q

What are the two differentiating characteristics of IgA?

A

Dimer (in mucosal form)

Can cross mucosal membranes

29
Q

What are the two subclasses of IgA? What is the major difference between them?

A

IgA1 and IgA2.

IgA1 can be cleaved by bacterial IgA1 protease, and fix complement (IgA2 cannot)

30
Q

In what form does IgA exist in the serum?

A

Monomer (not a dimer as it is found in mucus, saliva, etc)

31
Q

What is the MOA of IgA?

A

Opsonizes small pathogens for phagocytosis

Prevents binding of microbes to epithelium

32
Q

Eosinophilic degranulation occurs when it binds what part of the IgA antibody? What is this important for?

A

Fc-alpha-R

Parasitic immunity

33
Q

What are gamma/delta T cells?

A

Serve as antigen-nonspecific initial line of defense

Can respond to non-protein antigens

34
Q

What is difference between plasma cell migration from Peyer’s patches compared to T cells?

A

Same basic process

35
Q

What is the role of IL-8?

A

Inflammatory cytokine that upregulates the expression of cell adhesion molecules on epithelial cells + chemoattractant for PMNs

36
Q

What is the role of ICAM-1 on intestinal epithelial cells?

A

Binds PMNs to allow for extravasation

37
Q

What is the role of LFA-3?

A

Binds PMNs to allow for extravasation

38
Q

What is the role of E-selectin?

A

Binds PMNs to allow for extravasation

39
Q

What is the role of P-selectin? Where is this stored? What activates its release?

A

binds to PMNs to allow for extravasation

Stored in Weibel-palade bodies

TNF-alpha

40
Q

What are Weibel-palade bodies?

A

Vesicles found in endothelial cells that store vWF and P-selectin

41
Q

What cells secrete IL-1? Function?

A

Macrophages, monocytes and fibroblasts,

Increase adherence protein expression

42
Q

What cells secrete TNF-alpha? Function?

A

Inflammatory cytokine that is secreted by macrophages, CD4+ lymphocytes, and granulocytes

Pyrogen and acute phase protein

43
Q

What is oral tolerance?

A

The immune system does not respond to certain GI antigens since they may be needed for nutrition

44
Q

What is the MOA of high dose oral tolerance?

A

High doses causes a clonal deletion of antigen-specific lymphocytes

45
Q

What is the MOA of low dose oral tolerance?

A

Clonal anergy + regulatory T cells suppress immune responses

46
Q

What is selective IgA deficiency? Why is this not very symptomatic?

A

Not able to make IgA, thus are predisposed to mucosal infection

IgM can take on the role of IgA

47
Q

What is the antibody that mediates hypersensitivity type I reactions?

A

IgE

48
Q

What is the cause of Gluten intolerance?

A

Gliadin not broken down into amino acids

49
Q

What is the molecule that binds to gliadin, and allows for it to bind to MHC molecules?

A

transglutaminase

50
Q

What disease has an associated increase in gamma-delta cells?

A

Celiac disease

51
Q

What is the problem with continuing to eat gluten despise having celiac disease?

A

Increases the incidence of GI lymphoma and carcinoma

52
Q

What is ulcerative colitis?

A

Inflammation that is limited to the large bowel, causing ulcer formation and a loss of mucosal absorptive function

53
Q

What is the treatment o refractory ulcerative colitis? Why is this a definitive cure?

A

Total colectomy

Disease does not affect the small intestie

54
Q

What is Crohn’s disease?

A

Inflammatory disease that can affect any portion of the GI tract, causing granulomatous lesions in the terminal ileum and ascending colon

55
Q

What are the ssx of Crohn’s disease?

A

Obstructive symptoms
Abscess formation
Fistulas

56
Q

What is the treatment for Crohn’s disease? MOA?

A

Infliximab– anti TNF-alpha to reduce the inflammation

57
Q

Why is surgery for Crohn’s disease not a definitive treatment?

A

Disease tends to recur in unaffected areas of the bowel

58
Q

What is the primary difference between UC and CD?

A

UC = granulocyte inflammatory cell activation and abscess formation

CD = granulomatous lesions

59
Q

What are the two MOA of pernicious anemia (not including dietary deficiency)?

A

Anti-intrinsic factor

Anti-parietal cells

Gastrointestinal (42 decks)

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