Review
Copyright ©The Author(s) 2019.
World J Gastroenterol. Jul 21, 2019; 25(27): 3503-3526
Published online Jul 21, 2019. doi: 10.3748/wjg.v25.i27.3503
Table 1 Secretory substances produced by eosinophils
SubstanceCharacteristicsPre-prodiced or de novo synthesysedMain functionsRef.
Located within the core of specific (crystalloid) granules
Major basic proteins 1 and 2 (MBP1 and MBP2)Small highly cationic proteins (MBP2 is less basic)Pre-producedHighly cytotoxic to host cells, antihelminthic, antibacterial (MBP1 is more potent and associated with EETosis)[2,4,32,36]
Located within the matrix of specific (crystalloid) granules
Eosinophil cationic protein (ECP)Small highly cationic protein with a weak ribonuclease activity (ribonuclease 3)Pre-producedHighly cytotoxic to host cells, neurotoxic, antihelminthic, antibacterial, antiviral, associated with EETosis[2,4,32,36]
Eosinophil-derived neurotoxinSmall basic (less cationic than MBP1 and ECP) protein with a ribonuclease activity (ribonuclease 2)Pre-producedCytotoxic to host cells, neurotoxic, strongly antiviral, antibacterial,[2,4,32,36]
Eosinophil peroxidaseHighly cationic heme-containing haloperoxidasePre-producedGenerates ROS exerting potent antibacterial and antihelminthic effects[2,4,32,36]
Charcot-Leyden crystal protein (CLC, galectin-10)Small slightly acidic proteinProbably pre-producedUnclear, but involvement EETosis and a role in interactions between eosinophils and T-cells are suggested[31,32,36-38]
Most likely stored within specific granules, but some may be synthesised de novo in the cytoplasm
IL1β, IL2, IL3, IL4, IL5, IL6, IL10, IL11, IL13, IL16, IL18, IL25 (IL17E), IFNγ, GM-CSF, TGFα, TNFα, TNFβ, leukaemia inhibitory factorCytokinesMostly pre-produced; some may be de novo synthesisedA wide range of signaling and regulatory functions[4,5,32,39]
HB-EGF-LBP, NGF, PDGF, SCF, EGF, VEGF, APRILGrowth factorsPre-produced or de novo synthesisedSignalling functions related to cell proliferation and differentiation[4,5,32]
CCL3, CCL5, CCL6, CCL7, CCL8, CCL9, CCL11 (eotaxin-1), CCL13, CXCL1, CXCL8, CXCL10, CXCL12ChemokinesPre-produced or de novo synthesisedCell migration regulation[4,5,32,39]
Matrix metalloproteinases MMP9 and MMP17, acid phosphatase, collagenase, arylsulfatase B, histaminase, phospholipase D, catalase, non-specific esterasesEnzymesPre-produced or de novo synthesisedInflammation-related effector functions including cytotoxicity, extracellular matrix modification and phagocytosis[4,5,32]
Produced within the lipid bodies
Leukotrienes C4, D4 and E4, Thromboxane B2, Prostaglandins E1 and E2, 15-hydroxyeicosatetranoeic acid, platelet-activating factorLipid signalling factors, mostly eicosanoidsDe novo synthesisedA broad range of effects in inflammatory and allergic responses[4,5,34]
Table 2 Cell surface markers expressed by eosinophils
Group of surface markersMarkers identified for eosinophilsRef.
Cytokine and growth factor receptorsIL-2R, IL-3R, IL-4R, IL-5R, IL-9R, IL-10R, IL-13R, IL-17R, IL-23R, IL-27-R, IL-31R, IL-33R (ST2), TSLPR, GM-CSFR, KIT, IFNγR, TGFβR[5,43-45]
Chemokine and chemoattractant receptorsCCR1, CCR3, CCR4, CCR5, CCR6, CCR8, CCR9, CXCR2, CXCR3, CXCR4, FPR1, FPR2, C3aR, C5aR[5,43,44,46]
Lipid mediator receptorsPlatelet-activating factor receptor, DP1 prostaglandin receptor, DP2 prostaglandin receptor (CRTH2), EP4 prostaglandin receptor, E2 prostaglandin receptor, Leukotriene B4 receptor, Lysophosphatidylserine receptor P2Y10, S1P receptors[5,43,44,47]
Fc receptorsFcαR, FcγRII, FcγRIII, FcεRI, FcεRII[5,43,44]
Adhesion molecule receptorsIntegrin αLβ2 (LFA1), Integrin αMβ2 (CR3), Integrin αXβ2 (CR4), Integrin α4β1 (VLA4), Integrin α6β1, Integrin αDβ2, Integrin α4β7 (LPAM), cell surface adhesion receptor CD44, CD62L (L-selectin), PSGL1 (P-selectin lipoprotein ligand), CD34, CD244 (2B4)[5,43,44,48,49]
Pattern recognition receptorsTLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, TLR9, TLR10, NOD1, NOD2, RIG-1, RAGE[5,43,44]
Other receptors and surface markersPIRB, SIGLECs, SIRPα (shown for mice), LAIR1, Cannabinoid receptor CB2, Kinin B1 and B2 receptors, Histamine receptors, PAR1 or PAR2, CD80 or CD86, CD48, CD300 receptors (a and f), MHC class II[5,43,44,50-53]