Mucosal Immunity

Question 1

What are mucosal surfaces?

Answer 1

A body surface comprising a mucous membrane which lines body cavities and passages

Question 2

Functions of mucosal surface

Answer 2

Allows the host to interact with environment

Question 3

Examples of mucosal surfaces

Answer 3

GI tract
Respiratory tract
Urogenital tract

Question 4

Mucosal tissue epithelium types

Answer 4

Simple columnar epithelium
Pseudostratified columnar epithelium
Non keratinised stratified squamous epithelium

Question 5

Simple columnar epithelium lines…..

Answer 5

Stomach
Intestines
Biliary tract
Alveoli

Question 6

Pseudostratified columnar epithelium

Answer 6

Trachea
Bronchi
Bronchioles

Question 7

Non keratinized stratified squamous epithelium

Answer 7

Oral cavity
Esoophagous
Rectum
Nasal sinuses
Tonsils

Question 8

Mucosal surfaces consist of…

Answer 8

Epithelium
Mucus layer - secreted by goblet cells
Lamina propia - immune cells, BVs
Submucosa

Question 9

Functions of mucosal tissues

Answer 9

Barrier function - prevent pathogen entry
Selective permeability - allows nutrient absorption while blocking microbes
Immune surveillance
Interactions with commensals - maintains homeostasis with microbiota

Question 10

Intestinal epithelial cell types

Answer 10

Enterocytes
Goblet cells
Paneth cells
Enteroendocrine cells
Tuft cells
M cells
LGR5+ stem cells

Question 11

Enterocytes functions

Answer 11

Nutrient absorption
Microbial sensing
Ig transport

Question 12

Goblet cell functions

Answer 12

Produce mucins
This allows for mucus barrier

Question 13

Paneth cells function

Answer 13

Secrete antimicrobial peptides
- Alpha defensins, lysozyme

Question 14

Enteroendocrine cells

Answer 14

Release hormones - CCK, GLP-1, PYY
In response to nutrients/ microbes

Question 14

M cells function

Answer 14

Antigen uptake and delivery to peyers patches

Question 14

Tuft cells function

Answer 14

Produce IL-25
This activates type 2 innate lymphoid cells

Question 14

Immune cells involved in mucosal immunity

Answer 14

Intraepithelial lymphocytes
Dendritic cells
Macrophages

Question 14

LGR5+ stem cells

Answer 14

Renew the intestinal epithelium

Question 15

Paneth cells function

Answer 15

Secrete antimicrobial peptides
- Alpha defensins, lysozyme

Question 16

Intraepithelial lymphocytes

Answer 16

Antigen-experienced T cells embedded in the epithelium
Rapid cytotoxic responses

Question 17

Dendritic cells

Answer 17

Sample antigen, induce tolerance or immunity depending on context

Question 18

Macrophages

Answer 18

Highly phagocytic,
Anti inflammatory in homeostasis
Extend dendrites into lumen

Question 19

What does GALT include?

Answer 19

Peyer’s patches
Isolated lymphoid follicles
Lamina propria lymphocytes
Mesenteric lymph nodes

Question 20

Structures in peyers patch

Answer 20

Follicle associated epithelium with M cells
Sub epithelial dome with dendritic cells
B cell follicles with germinal centres
T cell zones
Efferent lymphatics

Question 21

Functions of peyers patch

Answer 21

Sample antigens directly from gut lumens Initiate adaptive immune responses - IgA class switching, T cell activation

Question 22

Steps of antigen presentation occurs in GALT to elicit cell mediated and humerol immunity

Answer 22

Antigen uptake Dendritic cel activation T cell differentiation B cell activation IgA transport

Question 23

Outcome of antigen presentation in GALT

Answer 23

Humerol immunity - secretory IgA neutralises pathogens, maintains microbiota Cell mediated - intraepithelial lymphocytes and effector T cells protect epithelium

Question 24

What does GALT stand for

Answer 24

Gut Associated Lymphatic Tissue

Question 25

Step 1 antigen presentation in GALT

Answer 25

Antigen uptake - multiple routes M cells transport antigen to dendritic cells Enterocytes transcytose antigen via Fc receptors Goblet cells deliver soluble antigens to DC Paracellular transport of small antigens Trans epithelial dendrites from DCs capture antigen

Question 26

Step 2 antigen presentation in GALT

Answer 26

DC activation. DCs in peyers patch or Lamina propria take up antigen They migrate to mesenteric lymph nodes Present antigen on MHC II to naive CD4+ T cells

Question 27

Step 3 antigen presentation in GALT

Answer 27

T cell differentiation - depending on signals Either Tolerance - IL-10, TGF-b from regulatory T cells Immunity - IL-12,6,1 from TH1,17 or 2 responses

Question 28

Step 4 antigen presentation in GALT

Answer 28

B cell activation. Occurs in peyers patch germinal centres Class switching to IgA (this is TGF beta dependent) Plasma cells migrate to laminate propria and secrete dimeric IgA

Question 29

Step 5 antigen presentation in GALT

Answer 29

IgA transport. IgA binds poly Ig receptors These are transcytosed to lumen to become secretory IgA