Mucosal Immune Response

Question 1

What are key factors that aid homeostasis

Answer 1

• Regulated and maintained by a system of checks / balances between pro inflammatory cells and immune regulatory cells
• TH1: Produce IFN-γ
• TH17: Produce IL-17a, 17f and IL-22
• Innate Lymphoid: Cytokine effector features resembling TH2 and TH17
• Anti Inflammatory: CD4, Foxp3, Tregs

Question 2

What are segmented filamentous bacteria

Answer 2

• Uncultivable spore forming bacteria of Firmicutes Clostridiales
• Present in intestinal tracts of diverse species
• Commensal organisms that have shown to directly contact IECs

Question 3

What role do SFB play in mucosal regulation of the immune response

Answer 3

• Stimulation of pro-inflammatory responses
• Induction of IL‑17 expression in T cells inthe lamina propria
• Stimulate IL-22 secretion
• Stimulate antimicrobial peptideREGIIIγ expression in the epithelium
• Induction of regulatory T cell responses

Question 4

What are innate lymphoid cells

Answer 4

• Lymphocytes of the GALT, BALT and NALT
• Play a critical role in protecting the body from harmful pathogens
• Lack expression of lineage / antigen specific markers
• Activated in response to cytokines / damage
• Coordinate lymphoid tissues, protect against pathogens

Question 5

What is ILC-1

Answer 5

• Composed of prototypical ILC, natural killer cells

- Express T-bet and IFN-γ, dysregulation leads to inflammation

Question 6

What is ILC-2

Answer 6

• Humoral responses
• Composed of innate helper cells (nuocytes)
• Express GATA-3 and produce Th2 type cytokines IL-5 and IL-13
• Important in helminth expulsion, dysregulation leads to allergies

Question 7

What is ILC-3

Answer 7

• Composed of lymphoid tissue inducer (LTi) cells and ILC-22 cells
• Innate regulatory cells
• Express ROR-γt / RORc TFs
• Dysregulation leads to autoimmunity, ILCP, Id2- expressing ILC precursors (IBD)

Question 8

What do common lymphoid progenitors give rise to

Answer 8

• ILCs: Lack Ag specific receptors / lineage markers
• TCRγδ: Localise to mucosal tissues (skin, gut, lung), non-classical MHC molecules (present on endothelial / epithelial), non-peptide antigens
• Invariant T Cells: Limited Vα-chain diversity, TCR recognition via non-classical Class I MHC proteins + specific ligand

Question 9

What are the subtypes of invariant T cell populations

Answer 9

• iNKT TCRαβ: Localise to liver and spleen, thymus, recognise glycolipids / CD1d
• MAIT TCRαβ: Localise to mucosal tissues, LNs, adipose tissue, restricted repertoire, recognise lipid glucose monomoylate and CD1b
• GEM T TCRαβ: Localise to mucosal tissues and LNs, restricted repertoire, recognise terins / MR1 (vitamin derived

Question 10

What is IL-17

Answer 10

• Secreted by TH17 (ILC-3) and innate lymphoid cells
• Homo-dimers
• Responsible for generation of lymphoid tissue (embryogenesis)
• Express ROR-γt / RORc TFs
• Crucial in antibacterial / fungal immunity and tissue repair
• Members A-F
• Regulated by ECs

Question 11

What role does IL-17 / LTi play in

immune effector responses

Answer 11

• Adaptive and immune regulation, A-F subsets
• Crucial in antibacterial / fungal immunity and tissue repair (A, A/F, F)
• Antibacterial responses (B, C) and humoral immune responses against parasites (D, E)
• IL-17c (autocrine), secreted in response to tissue damage (TNFa / IL-1b)
• IL-17e regulates Th2 responses at mucosal surface, increase CD4 Treg conc.

Question 12

What is IL-22

Answer 12

• Secreted by TH17 and TH22 (ILC-3)
• Activates ILC22 and ILC17
• Induces proliferative and anti-apoptotic pathways
• Anti-microbial molecules, that help prevent tissue damage and aid in its repair