Innate cell |
PRRs/activating receptors |
Products/molecules |
Innate function |
DC (general) |
TLRs, CLRs, RLRs, NLRs |
Various |
Immune sentinels; proinflammatory or anti-inflammatory effects |
LC |
Langerin/CD207 (CLR)
FcγR and FcεR
DEC205 |
Chemokines CCL2, CCL17 and CCL22 |
Attraction of other leukocytes to sites of inflammation |
Surface molecules ICOS-L |
Inhibition of T-cell responses (immune tolerance) |
Enzyme IDO |
Immunoregulatory activity |
dDC (mDC) |
TLR2, TLR4, CD206, DC-SIGN (CD209) |
CCL17, CCL22 |
Attraction of other leukocytes to sites of inflammation |
TNF and iNOS |
Proinflammatory effects |
dDC (pDC) |
TLR7, TLR9 |
Type 1 IFNs |
Immunity against viral infections and promote function of T-cells, B-cells, NK cells |
Keratinocyte |
TLR1, TLR2, TLR4, TLR5, TLR6 (cell surface) and TLR3, TLR9 (endosomes) |
AMPs: β-defensins and cathelicidin |
Anti-microbial defence |
AMP: LL37 |
Loss of immune tolerance |
IL-1, IL-6, IL-10, TNF, TGFβ |
Broad range of effects |
CXCL1, CXCL8 |
Mediate attraction of neutrophils and other immune cells to inflamed skin via CXCR2 expression |
Neutrophil |
TLRs (excluding TLR3 and TLR7) |
IL-1α, IL-1β, TNF, IL-6 |
Host defence |
Chemokine CXCR2 |
Migration towards CXCL1- and
CXCL8-expressing keratinocytes in inflamed skin |
Adhesion molecules L-selectin and LFA-1 (αLβ2) |
Promote neutrophil rolling, adhesion and diapedesis for recruitment to skin |
AMPs: cathelicidins, lysozyme, α-defensins |
Direct microbicidal activity |
Proteinases: cathepsin G, neutrphil elastase and proteinase 3/myeloblastin |
Contain acid hydrolases to degrade bacterial components |
Proteins: lactoferrin, transcobalamin II, NGAL and calpotectin |
Sequester essential nutrients to limit bacterial growth |
Classically activated macrophage |
TLRs (T-cell/NK cell-derived IFNγ and macrophage-derived TNF needed in combination with TLR ligation for macrophage activation) |
IL-12 |
Induces IFNγ production from T-cells and NK cells |
TNF |
Activates macrophage (second signal) |
IL-23 |
Promotes inflammatory immune responses |
Toxic intermediates (NO and ROI) |
Bactericidal activity |
Alternatively activated macrophage |
TLRs (CD40/CD44 signalling can occur instead of TLR ligation). FcγR ligation by IC required in combination with TLR ligation for activation |
IL-10/no IL-12/no toxic intermediates |
Potent anti-inflammatory effects |
G-CSF |
Anti-inflammatory effects via DC modulation |
Fibronectin, βIG-H3 |
Fibrogenesis promoting tissue repair and collagen formation |
Arginine |
Polyamine and proline synthesis promoting cell growth and tissue repair |
Mast cell |
TLRs (murine skin MC express TLR3, TLR7, TLR9) |
TNFα, IL-1, IL-6, IL-10, lipid mediators (PG and LT) |
Contribute to allergic and inflammatory responses |
Chemokines |
Recruitment to skin |
NK cell |
NKG2A, NKG2D (stressed/dying cells)
TLR3, TLR9 (exogenous microbes) |
IFNγ, TNFα |
Cytotoxicity and inflammation |
IL-22 (in response to IL-23) |
AMP production, host defence, constraint of inflammation |
IL-17 (in response to zymosan) |
AMP production and host defence |
Chemokines CXCR3, CCR5 and CCR6 |
Migration towards CXCL10, CCL5 and CCL20 on keratinocytes of inflamed skin |
NKT cell |
Invariant TCRα chain combined with limited set of TCRβ chains |
IFNγ, IL-4, IL-2, IL-5, IL-10, IL-13, TNFα |
Inflammatory and allergic responses |
Perforin, granzymes, FasL, TRAIL, granulysin |
Cytotoxicity |
γδ T-cell |
TLRs (microbial recognition)
Vδ1 receptor (stressed/dying cells and tumour cells)
NKG2D (stressed/dying cells and tumour cells) |
IL-2, IFNγ, TNFα |
Inflammation |
CCL3, CCL4, CCL5, XCL1 |
Chemotaxis to recruit cells to site of damage |
KGF |
Tissue repair/wound healing |
IGF-1, IL-2 |
Epidermal maintenance and development |
IL-17 |
Host defence |
