Innate Immunity in the Intestine

Transcription

1 Master s course in biomedical sciences Innate Immunity in the Intestine Dr. Kathy McCoy February 26 th,

2 Host-Microbial Homeostasis: Innate Immunity Pharynx & upper respiratory tract ~ Barriers - Sensing the microbiota acid in stomach (Helicobacter pylori) Distal small intestine (ileum) CFU/ml Large intestine (colon) 1012 CFU/ml ~ Antimicrobial peptides - Sampling the microbiota - Intestinal mononuclear cells - Innate lymphoid cells Skin CFU/ml ~1011 2

3 Barriers: Physical, chemical, immune Lumen Mucus Commensal bacteria Enterocyte SFB CX 3 CR1 + DCs Macrophage IgA Goblet cell AMPs M cell CD103 + CD11b + DCs Tregs B cell CD103 + CD11b - DCs Enterodocrine cell Lamina Propria Stem cell Paneth cells Th17 Peyer s Patch Plasma cells FIGURE 1 Intestinal mucosal surface at the steady state. The intestinal epithelial barrier is a highly organized mucosal surface that prevents the entry of microbes into the lamina propria. The epithelium is constituted of a single layer of intestinal epithelial cells (IECs) covered by a stratified mucus layer. epithelial stem cells that proliferate and give rise to daughter cells. These cells include enterocytes, mucus-producing goblet cells, hormone-producing enteroendocrine cells, AMP-producing Paneth cells at the base of the crypts and finally, M cells that sample antigens from the intestinal lumen in order to 3

4 Epithelial cell tight junctions b Microvilli -Regulators of paracellular transport Claudin Occludin ZO1 MLCK F-actin Myosin -catenin 1 Tight junction - Proinflammatory cytokines (IFNγ, TNFα) can increase intestinal permeability E-cadherin Adherens junction -catenin Keratin Desmoglein Desmocollin Desmoplakin Desmosome 4

5 Mucus thickness differs along the intestine Stomach Small intestine Large intestine 10 3 /g Bacterial load /g 800 Mucus thickness (µm) Bacteria Bacterial products MAMPs Metabolites Isolated lymphoid follicles (ILF) Ileum Colon Outer layer Antrum 200 Corpus Duodenum Jejunum 100 Inner layer ILF ILF ILF Peyer s patch Immune system 5

6 Inner mucus layer is sterile - mucins seceted by goblet cells oligomerise to form a sticky gel - there are two layers of mucus - muc2-/- mice spontaneously develop colitis Vaishnava et al 2011 Science 334:255 6

7 Paneth cells secrete antimicrobial proteins b Human BD1, BD2, Lysozym Host-derived AMP BD3 and BD4 SLPI (AMP)Staphylococcus Cathelicidin Antimicrobial a proteins such as REG3γ Mucus layer RNase7 Psoriasin Lactoferrin epidermidis αmsh Catesta Calprot - small intestinal enterocyte express REG3γ & REG3β - large intestinal enterocytes express β-defensins and cathelicidins Enterocyte Goblet cell Mucin Antimicrobial proteins such as α-defensins, ANG4 and REG3γ -many AMP target cell or cell membrane functions Cathelicidin through enzymatic (eg lysozyme) and non-enzymatic disruption (defensins) Mast cell Sebocytes Paneth cell Human BD1, BD2 and BD3 Histone H4 Psoriasin Cathelicidin Cathe Dermc Huma and BD Eccrin gland E Nature Reviews Immunology 504 JULY 2012 VOLUME 12 Figure 1 Epithelial barriers of the intestine and skin. a The intestinal epithelium 7

8 Antimicrobial proteins families Table 1 Major antimicrobial protein families in skin and intestine Family α-defensins (cryptdins in mice) Representative proteins DEFA5, DEFA6 (in humans); cryptdins 1 16 (in mice) Mechanism of action Membrane disruption β-defensins BD1, BD2, BD3 Membrane disruption; lipid II binding (BD3) Calprotectin (S100A8 S100A9) Cathelicidins C-type lectins Tissue sites of expression Small intestine Large intestine, skin, respiratory tract Cellular sites of expression Paneth cells, neutrophils, macrophages Enterocytes, keratinocytes, respiratory tract epithelial cells Target organisms Gram-positive bacteria, Gram-negative bacteria, fungi, viruses, protozoa Gram-positive bacteria, Gram-negative bacteria, fungi, viruses, protozoa Refs 8 86,133 NA Metal chelation Abscesses Neutrophils Staphylococcus aureus 39 LL37 (in humans); CRAMP (in mice) HIP/PAP (in humans); REG3γ (in mice) Membrane disruption Peptidoglycan recognition; killing mechanism unknown Large intestine, skin, lung, urinary tract Small intestine Neutrophils, mast cells, epithelial cells Epithelial cells (Paneth cells, enterocytes) Galectins GAL4, GAL8 Unknown Intestine Broad expression, including by epithelial cells Lipocalin Lipocalin 2 Sequestration of iron-laden siderophores Lysozyme NA Enzymatic attack on bacterial cell wall peptidoglycan Peptidoglycan recognition proteins PGLYRP1 4 in mammals Activation of bacterial two-component systems; PGLYRP2 is an amidase that targets peptidoglycan Phospholipase A2 NA Hydrolysis of bacterial membrane phospholipids Broad expression, including intestine and lung Intestine, eye, and more; secretions, including tears, saliva Liver, intestine, skin, mammary gland Intestine; secretions, including tears, inflammatory fluids Macrophages, epithelial cells Intestinal Paneth cells Epithelial cells Paneth cells, macrophages Gram-positive bacteria, Gram-negative bacteria, viruses, fungi 36 Gram-positive bacteria 11,12, 23 Bacteria bearing blood group antigens 134 Escherichia coli 135, 136 Gram-positive bacteria; some activity against Gram-negative bacteria Gram-positive and Gram-negative bacteria Gram-positive bacteria 139 Psoriasin (S100A7) NA Unknown Skin Keratinocytes Escherichia coli 12 RNases ANG4, RNase7 Unknown Skin, intestine Epithelial cells Gram-positive and Gram-negative bacteria 26,38 Nature Reviews Immunology 504 JULY 2012 VOLUME 12 8

9 Innate immune receptors: pattern recognition -Toll-like receptors: bacterial and viral molecules -Mannose receptor: microbial surface carbohydrates -NOD receptors bacterial peptidoglycans 9

10 PRR signalling in intestinal epithelial cells A B Pathogens Commensal bacteria Commensal bacteria NOD1/2 TLR Defensins Alpi RegIIIγ Insufficient epithelial signallin Reduction of mucosal antibacte Loss of epithelial barrier integrit Impaired epithelial repair capac? RLR TLR ROS IL-17C SIGIRR A20 PPARγ IKK1/2 NEMO RelA IL15 IL-7 IEL? proil1β proil-18 Inflammasome ACUTE SITUATION Altered cell composition and tissue homeostasis Reduced nutrient and water absorption Clinical disease CX 3 CR1 + Proliferation Differentiation Cell survival CCL20 CCL28 April TSLP TGFβ IL1β IL-18 CHRONIC SITUATION Perpetuating inflammation Altered microbiota composition Progressive tissue destruction EMBO Chronic reports disorder VOL 13 NO (e.g. Inflammatory bowel disease) 10

11 quantified by Q-PCR determination of 16S rrna / gene copy number in the terminal ileum. N = 5 mice per position between Myd88 and wild-type mice did not exhibit reduced mucus p genotype. Data are from three groups of littermates. *, P < 0.05; error bars, mean TSEM; ns, not significant. (fig. S2, A and B). The increase in mucosa- or secretion (fig. S3, A and B). T associated bacteria was unlikely to result from a gest that MyD88-dependent inna Epithelial cell MyD88 is required for excluding bacteria from inner mucus layer Fig. 1. MyD88 promotes p of the microbiota and th surface. (A) Visualization of ization relative to the small surface by FISH. Sections we probe that recognizes the 1 all bacteria (green) and co 4,6-diamidino-2-phenylind sualize nuclei (blue). Scale b indicate thewith distance Fig. 2. Epithelial cell MyD88 is necessary and sufficient to limit bacterial association the from smallt DIEC Tg 11

12 Antimicrobial peptides: Constitutive & regulated Subset of α-defensins expressed independently of the microbiota Bacteria Subset of regulated α-defensins REG3γ Cathelicidin β-defensins Kerat MDP MAMP MYD88 Epithelium TCF4 NOD2 NF-κB TLR MYD88 CYP27B1 Keratino hyperpro Paneth cell Enterocyte IL-22R 1,25-OH vitamin D3 25-OH vitamin D3 Lamina propria IL-22 Endosome T H 17 mat Innate lymphoid cell TLR9 Dendritic cell Type I IFN Nature Reviews Immunology 504 JULY 2012 VOLUME 12 12

13 Innate cells: Sampling the microbiota 8 JUNE 2012 VOL 336 SCIENCE 13

14 Intestinal mononuclear phagocytes: macrophages and dendritic cells Immunol Res DOI /s

15 - Critical role in the maintenance of intestinal homeostasis - Act without antigen-specific receptors Innate lymphoid cells Precursor% Id2&dep& RORγt&dep& GATA;3&dep& T;bet&dep& LTi 4 % RORγt + &ILC& LTi 0 % IL017 + %% ILC% IL022 + %ILC% %(NKp46+% ILC)% ILC1% Thymic%NK% NK&cells&& & & cnk% %cells% ILC2,&nuocytes&& & ILC2% IL017% IL022% IFNγ% IL04,5,%13% Lymph organs formation Tissue repair after injury Colitogenic cells Extracellular bacteria Protection against microbial pathogens Extracellular parasites Wojno%Cell%host%&%microbe%2012% Spits%et%a.%Annu%Rev%Immunol%2010% 15

16 Innate immunity controls intestinal homeostasis CX3CR1 + MP TSLP Granulocytes IL 22 IL 17 IFN CD103 + DC ILC γδ TGF RA IL 18 IL 23 Macrophage siga IL 12 IL 1 IL 6 IL 10 T reg B cell TNF a T eff IL 10 TGF NK b Th1 Th17 16

17 Balanced innate immune activation maintains intestinal homeostasis Intestinal inflammation Level of innate immune activation Hyporesponsive Homeostasis Hyperresponsive IEC integrity + proliferation Anti-microbial peptide production Mucus, AMP, siga and IEC barrier PRR compartmentalization Myeloid MAMP detection Pro inflammatory cytokines + chemokines Luminal sampling Tolerogenic DCs Tolerogenic pathways Pathogen/parasite clearance PRR activation of IEC Innate regulatory cytokines Leucocyte accumulation + activation IEC proliferation 17