EXAM #1: IMMUNOLOGY OF THE GI TRACT Flashcards Preview

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Flashcards in EXAM #1: IMMUNOLOGY OF THE GI TRACT Deck (48):
1

What is the big difference between mucosal immunity and "normal" immunity?

*Length of time*

-->Mucosal immunity does NOT last very long

2

How long do mucosal antibody responses last?

Months to a year

(vs. serum antibodies that persist for decades/life)

3

What are effector cells?

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

4

What is tertiary lymphoid tissue?

Any place in the body that becomes infected by microorganisms

5

What kind of lympoid tissue is the gut considered?

Tertiary

6

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

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

7

What is GALT?

Gut Associated Lymphoid Tissue

8

List the sites of GALT.

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

9

What is a Peyer's Patch?

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

10

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

1) IgA antibodies
2) CTL

11

Describe the structure of a Peyer's Patch.

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

12

Where are APCs located in the Peyer's Patch?

T-cell rich areas adjacent to the Germinal Center

13

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

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

****Note that M-cells are sites of infection*****

14

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

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

15

What are IELs?

Intraepithelial Lymphocytes i.e. between enterocytes in the epithelium

16

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

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

*Classic T-cell

17

What is the function of CD8+ IEL cells?

Cell-mediated immunity against:
1) Viral antigens
2) Intracellular bacterial antigens

18

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

Lamina Propria

vs. CD8+ T-cells in the epithelium

19

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

- B-lymphocytes
- Plasma cells
- Macrophages
- Dendritic cells
- Eosinophils
- Mast cells

20

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

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

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

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

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

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

23

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

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

What is "secretory component?"

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

25

What is the function of secretory component?

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

26

What is the major immunoglobulin in secretions?

IgA

27

What are the two subclasses of IgA?

IgA1=
- cleaved by bacterial IgA protease
- can fix complement via alternate pathway

IgA2= not susceptible to IgA protease

28

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

Mucosal= IgA dimer

Serum= monomer

29

What is the role of IgA in immunity?

1) Opsonization of small pathogens for phagocytosis
2) Anti-parasite immunity by facilitating eosinophil degranulation

30

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

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

What is the importance of mast cells in gut immunity?

1) Play a role in IgE-mediated immunity against parasites
2) Elicit food-induced allergic reactions

32

What is oral tolerance?

Prevention of an immune response to the food you eat

33

What is high dose tolerance?

Clonal deletion of antigen specific lymphocytes

34

What is low dose oral tolerance?

Clonal anergy and T-reg suppression of the immune response

35

What is the most common immunodeficiency?

Selective IgA deficiency

36

What is the clinical presentation of Selective IgA deficiency?

Most are Asymptomatic but have a higher risk for Autoimmune disease

****Remember the A's*****

37

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

IgM

38

What class of antibody mediates Food Hypersensitivity?

IgE

39

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

Gliadin

40

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

Gluten-Sensitive Enteropathy

41

What is the treatment for Gluten-Sensitive Enteropathy?

Lifelong gluten-free diet

42

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

1) GI Lymphoma
2) GI Carcinoma

43

What is the pathologic feature of Ulcerative Colitis?

Inflammation of the large bowel

44

What is the definitive treatment for Ulcerative Colitits?

Total Colectomy

45

What is the pathologic feature of Chron's Disease?

Inflammatory AND granulomatous lesions of the terminal ileum and ascending colon

46

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

Infliximab-- anti-TNF-alpha monoclonal antibody

47

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

Granulocyte inflammatory cells= UC

Granulomatous lesions= CD

48

What is the most common cause of Pernicious Anemia?

Autoimmune antibodies against IF or gastric parietal cells