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Gastrointestinal System > EXAM #1: IMMUNOLOGY OF THE GI TRACT > Flashcards

EXAM #1: IMMUNOLOGY OF THE GI TRACT Flashcards

1
Q

What is the big difference between mucosal immunity and “normal” immunity?

A

Length of time

–>Mucosal immunity does NOT last very long

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2
Q

How long do mucosal antibody responses last?

A

Months to a year

vs. serum antibodies that persist for decades/life

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3
Q

What are effector cells?

A

Lymphocytes that are “primed” to preform function immediately on contact with antigen

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4
Q

What is tertiary lymphoid tissue?

A

Any place in the body that becomes infected by microorganisms

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5
Q

What kind of lympoid tissue is the gut considered?

A

Tertiary

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6
Q

What are the physical mechanisms that prevent infection of the GI tract?

A

1) Acidity of stomach
2) Peristoltic motility
3) Detergent action of bile
4) Mucus secretion

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7
Q

What is GALT?

A

Gut Associated Lymphoid Tissue

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8
Q

List the sites of GALT.

A

1) Peyer’s patches
2) Appendix
3) Lymphoid aggregates in appendix/ large intestine
4) Lymphoid cells in lamina propria

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9
Q

What is a Peyer’s Patch?

A

Aggregates of lymphoid tissue found in the ileum of the small intestine

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10
Q

What types of immunity are generated by Peyer’s Patches?

A

1) IgA antibodies

2) CTL

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11
Q

Describe the structure of a Peyer’s Patch.

A
  • M-cells within the membrane of microfolds
  • B-cell rich follicle
  • T-cell area
  • Germinal center
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12
Q

Where are APCs located in the Peyer’s Patch?

A

T-cell rich areas adjacent to the Germinal Center

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13
Q

What is the function of M-cells in Peyer’s Patches?

A

1) Uptake of antigen by endocyotsis and phagocytosis
2) Presentation of antigen to APCs

Note that M-cells are sites of infection*

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14
Q

List the microorganisms that utilize M-cells for introduction into the body?

A

1) Shigella–gets in via M-cells and then uses actin rockets to infect
2) Salmonella
3) Yersinia
4) Listeria

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15
Q

What are IELs?

A

Intraepithelial Lymphocytes i.e. between enterocytes in the epithelium

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16
Q

What type of lymphocytes are most IELs? What are the two subtypes of these cells?

A

T-cells

1) Alpha-Beta subtype*
2) Gamma-delta

*Classic T-cell

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17
Q

What is the function of CD8+ IEL cells?

A

Cell-mediated immunity against:

1) Viral antigens
2) Intracellular bacterial antigens

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18
Q

Where are CD4+ T-cells located in the gut wall?

A

Lamina Propria

vs. CD8+ T-cells in the epithelium

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19
Q

In addition to CD4+ T-cells, what other immune cells are in the lamina propria?

A
  • B-lymphocytes
  • Plasma cells
  • Macrophages
  • Dendritic cells
  • Eosinophils
  • Mast cells
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20
Q

Describe the basic immune response in the gut that results in IgA production.

A

1) M-cells uptake antigen
2) APCs bind antigen
3) APCs stimulate T-helper cells
4) T-helper cells stimulate antigen specific B-cells

21
Q

Once B-cells have been stimulated, outline the path that the cell will take to find the Lamina Propria.

A

1) Pre-plasma cells leave Peyer Patch via efferent lymphatic capillaries
2) Migrates via mesenteric lymph channels
3) Enter bloodstream via the thoracic duct
4) Go “home” to the Lamina Propria

22
Q

What is the role of addressins in B-cell stimulation?

A

These are the “homing” mechanisms that tell B-cells to go back to the Lamina Propria

23
Q

How do IgA secreting Plasma Cells get from the Lamina Propria to the gut lumen?

A

1) IgA binds “poly-immunoglobulin receptors” on basolateral side of enterocyte
2) Endocytosis and transport to apical side
3) Release of IgA dimer + secretory component

24
Q

What is “secretory component?”

A

Part of the poly Ig receptor that facilitates endocytosis of the IgA secreting plasma cell

25
Q

What is the function of secretory component?

A

Prevents the breakdown of IgA in the gut lumen by proteolytic enzymes

26
Q

What is the major immunoglobulin in secretions?

A

IgA

27
Q

What are the two subclasses of IgA?

A

IgA1=

  • cleaved by bacterial IgA protease
  • can fix complement via alternate pathway

IgA2= not susceptible to IgA protease

28
Q

What is the difference between the structure of IgA in the serum vs. mucousal sites?

A

Mucosal= IgA dimer

Serum= monomer

29
Q

What is the role of IgA in immunity?

A

1) Opsonization of small pathogens for phagocytosis

2) Anti-parasite immunity by facilitating eosinophil degranulation

30
Q

What is the role of gamma-delta T-cells?

A

1) Respond to NON-PEPTIDE antigen
2) Don’t recognize normal MHC

Quick immune response to pathogens that we are routinely exposed to without having to go through the entire process of normal T-cells*

31
Q

What is the importance of mast cells in gut immunity?

A

1) Play a role in IgE-mediated immunity against parasites

2) Elicit food-induced allergic reactions

32
Q

What is oral tolerance?

A

Prevention of an immune response to the food you eat

33
Q

What is high dose tolerance?

A

Clonal deletion of antigen specific lymphocytes

34
Q

What is low dose oral tolerance?

A

Clonal anergy and T-reg suppression of the immune response

35
Q

What is the most common immunodeficiency?

A

Selective IgA deficiency

36
Q

What is the clinical presentation of Selective IgA deficiency?

A

Most are Asymptomatic but have a higher risk for Autoimmune disease

Remember the A’s*

37
Q

What compensates for the absence of IgA in Selective IgA Deficiency?

A

IgM

38
Q

What class of antibody mediates Food Hypersensitivity?

A

IgE

39
Q

In Gluten-Sensitive Enteropathy, what protein is the immune response directed against?

A

Gliadin

40
Q

In what disease is there an increase in gamma-delta T-cells?

A

Gluten-Sensitive Enteropathy

41
Q

What is the treatment for Gluten-Sensitive Enteropathy?

A

Lifelong gluten-free diet

42
Q

What diseases are patients with Gluten-Sensitive Enteropathy at risk for?

A

1) GI Lymphoma

2) GI Carcinoma

43
Q

What is the pathologic feature of Ulcerative Colitis?

A

Inflammation of the large bowel

44
Q

What is the definitive treatment for Ulcerative Colitits?

A

Total Colectomy

45
Q

What is the pathologic feature of Chron’s Disease?

A

Inflammatory AND granulomatous lesions of the terminal ileum and ascending colon

46
Q

What drug can be used to treat Chron’s Disease?

A

Infliximab– anti-TNF-alpha monoclonal antibody

47
Q

What disease is characterized by granulocyte inflammatory cells? Which is characterized by granulomatous lesions?

A

Granulocyte inflammatory cells= UC

Granulomatous lesions= CD

48
Q

What is the most common cause of Pernicious Anemia?

A

Autoimmune antibodies against IF or gastric parietal cells

Gastrointestinal System (42 decks)

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