Mucosal Immunity Flashcards
Layers of defence at the mucosae
Pre-epithelial: Gastric acid (pH gradient maintained by bicarbonates and mucus layer) , Mucus layers (Loosely adherent & firmly adherent ),Antimicrobial peptides, Secretory IgAs (T cell-dependent & independent), Commensals
Epithelial: Epithelial cells that produce antimicrobial peptides, including RegIII gamma (Myd88-dependent), HD-5, HD-6
Subepithelial: Innate & Adaptive Immunity
Innate and adaptive cells in mucosal homeostasis
Innate immune cells:
CD103+ DCs: Activate latent TGF-beta in an integrin-dependent fashion; Produce retinoic acid
CX3CR1+ macrophages: Can capture luminal bacteria across mucosal epithelium and can phagocytose any translocating commensals.
ILCs:
ILC1: Secrete pro-inflammatory cytokines like IFN-gamma and TNF-alpha to activate marophages neutrophils; Promote the elimination of intracellular pathogens
ILC2: Early source of Th2 cytokines, including IL-13 and IL-5 to enhance the expulsion of worms/parasites; Can interact with Th2 via MHCII:TCR to promote its own survival through IL-2
ILC3: Can produce pro-inflammatory cytokines like IL-17A/F to protect against extracullar bacteria/fungi; Can produce IL-22 to promote epitheial barrier function; Also express MHCII to induce the apoptosis of commensal-specific T cells; Can induce Treg generation indirecly through Csf-2-dependent IL-10 and retinoic acid production from DCs and macrophages
Adpative immune cells:
Intraepithelial T cells: Common in small intestine & rare in large intestine; Usually CD8+ and many are gamma-delta T cells
Lamina propria lymphoctes: Th1, Th2, Th17, Tregs
