Host Defenses within the GI Tract

Question 1

What are the four layers of defense?

Answer 1

Intraepithelial barrier, Lamina propria, Peyer’s Patches and Mesenteric lymph nodes

Question 2

What is the Intraepithelial barrier?

Answer 2

Epithelium of small intestine. Site for effector T cells and expansion of memory/effector T cell populations. Mucosal barrier.

Question 3

What is the Lamina Propria?

Answer 3

Connective tissue of the gut mucosa, restricted to stoma above the muscularis mucosa. Just below epithelial layer. Effector phase – do not recognize novel material, do not mount immune response. Just recognize agent and destroy it immediately.

Question 4

What are Peyer’s Patches?

Answer 4

Inductive site for mucosal immune system. Site for B2 lymphocyte development, class switching, and production of secretary IgA. Antigen is delivered by a specialized epithelial cell (M cell) to professional APCs to prime naive T cells. No afferent lymphatics.

Question 5

What are Mesenteric lymph nodes?

Answer 5

Receive afferent lymphatic drainage. Site for B2 development and maturation of IgA/E/G producing plasma cells.

Question 6

When do Peyer’s patches begin to take form?

Answer 6

11 weeks gestation

Question 7

When do CD4+, DC, B and T cels regions take form?

Answer 7

19 weeks gestation

Question 8

When do germinal centers appear?

Answer 8

Not until after birth

Question 9

Where are peyer’s patches located?

Answer 9

Distal ileum predominantly (containing between 5-100 lymphoid aggregates)

Question 10

How does number of Peyer’s Patches vary with age?

Answer 10

50 at beginning of third trimester, 100 at birth, 250 in late adolescence, decreasing to 10 in late years (over 70 yrs)

Question 11

How does ILF - isolated lymphoid follicles change through out the gut?

Answer 11

ILF density increases distally through the gut. 1 ILF per 269 villi in the jejunum and 1 ILF per 28 villi in the ileum

Question 12

What are seven defense strategies in the immune system?

Answer 12

Block entry into organism, Block entry into the cell, Prohibit spreading, Direct killing, Kill infected host cell, Expulsion, Nutrient deprivations

Question 13

What is an important contributor to immune tolerance?

Answer 13

T regs

Question 14

What are anti-inflammatory cytokines?

Answer 14

IL-10, IL-1ra

Question 15

What are pro-inflammatory cytokines?

Answer 15

TNF-alpha, INF-gamma, IL-12

Question 16

What are cellular mediators of acute inflammation in Adaptive immunity?

Answer 16

Th1 cells, IFN-gamm, M1 macrophages, IgG, IgA, cytotoxic T cell, NK cell

Question 17

What are cellular mediators of chronic inflammation in Adaptive immunity?

Answer 17

Th2/17 cells, IL-4, IL-17, M2 macrophages, IgE (reaginic Ab), eosinophils, basophils

Question 18

After macrophages/monocytes consume bacteria/pathogen, what do they release to activate Macrophages/monocytes?

Answer 18

Pro-IL-18 which they release as IL-18

Question 19

What do macrophages with engulfed pathogen release to activate cytotoxic T cells?

Answer 19

IFN-gamma and IL-2

Question 20

What do macrophages with engulfed pathogen release to activate neutrophils?

Answer 20

IL-12 and IL-18

Question 21

What do macrophages with engulfed pathogen release to activate Th1 cells?

Answer 21

INF-gamma

Question 22

What do Th1 cells release to activate macropahges/monocytes?

Answer 22

IL1-beta, TNF-alpha

Question 23

What do activated macrophages/monocytes release as inflammation?

Answer 23

IL-1beta, TNF-alpha, CCL8, FasL