Special Lecture: Mucosal Immunology

Question 1

Immunological ignorance

Answer 1

The immune system is “not aware” of the microbe, because of physical separation

Question 2

Immunological Exclusion

Answer 2

IgA binds to the microbe and keeps it away from immune cells.

Question 3

Antimicrobial peptides

Answer 3

keep bacteria away from immune tissue

Question 4

The crypt

Answer 4

Region of epithelial cells close to the immunological tissue. We don’t want symbiotic microbes here.

Question 5

What role do goblet cells play in immunity?

Answer 5

Goblet cells generate mucous to keep microbes from immunological tissue.

Question 6

What role does IgA play in mucosal immunity?

Answer 6

IgA is the dominant form of immunoglobulin. It is found in the mucus, tears, saliva, and breast milk. IgA is a major factor involved in host-microbe dialogue at mucosal sites

Question 7

IgA at epithelial surfaces

Answer 7

IgA binds to toxins, and pathogens in the GI tract.

Question 8

TLR2/4

Answer 8

recognize LPS; lowered expression in healthy IEC; slightly elevated in IEC that have not yet migrated up the villi; limited availability of co-receptors MD-2, CD14 and LPS-binding protein (LBP)

Question 9

TLR5

Answer 9

recognizes flagellin; only expressed basolaterally

Question 10

TLR3

Answer 10

recognizes dsRNA; expressed immediately beneath the luminal surface

Question 11

TLR9

Answer 11

recognizes unmethylated bacterial DNA; basolateral TLR9 activation elicits a classic inflammatory response whereas apical TLR9 attenuates that response

Question 12

Intraepithelial lymphocytes

Answer 12

CD8+ or CD4+; Involved in inhibition or activation depending on what they encounter.

Question 13

Lamina-proprial lymphocytes

Answer 13

CD4-CD8-ab or CD4-CD8-gd

Question 14

M cells

Answer 14

Microfold cells - naked areas in the epithelial cells not covered by mucous, that take up antigen, present to APCs; Dendritic cells can also extend through the epithelium and sample for antigen.

Question 15

Th17

Answer 15

Clearance of extracellular pathogens (Klebsiella, Citrobacter, fungi) via neutrophil recruitment ;plays a role in Tissue inflammation; Immunopathology & autoimmunity

Question 16

Healthy (Probiotic) Microbes

Answer 16

Lactobacillus spp; Bifidobacterium spp; Faecalibacterium prauznitsii

Question 17

Colitogenic (Disease causing) microbes

Answer 17

Klebsiella pneumoniae; Proteus mirabilis; Adherent and invasive E. coli; Helicobacter spp.

Question 18

What microbial family is important in CD4 T reg development?

Answer 18

Clostridium is FOXP3 producing.

Question 19

What microbe promotes the formation of Th17?

Answer 19

SFB; Segmented Filamentous Bacteria.

Question 20

What are some of the functions of gut bacteria?

Answer 20

1) Extracting nutrients from food 2) competitive exclusion of pathogens 3) Epithelial cell maturation 4) lymphocyte development 5) immune regulation/homeostasis 6) overcoming dietary restrictions (degrading dietary polysaccharides)

Question 21

Immunological tolerance

Answer 21

The immune system is “aware” of the microbe but is not responsive because of active regulatory mechanisms.