ILC2

Scope

This entity page defines group 2 innate lymphoid cells (ILC2s) as they are used in the ILC-in-lung wiki. It is the canonical ILC2 hub for this wiki.

Use this page when the question is "what is the current source-aware ILC2 model in lung biology?" Then move to disease or regulation topics when you need a narrower branch.

Evidence tags

#entity/cell_type #cell/ILC2 #tissue/lung #topic/pulmonary_disease #topic/regulation #status/working

At a glance

Lens	Current take
Canonical role	Lung ILC2s are tissue-positioned type 2-biased innate lymphocytes that can drive allergic airway inflammation, but they also support repair and niche remodeling after respiratory injury.
Strongest pulmonary branches	Allergic amplification, viral AHR versus repair, macrophage-niche instruction, COPD-associated ILC1-like conversion, and IL-17-producing boundary states.
Strongest regulatory layers	Epithelial alarmins, lipid mediators, neuroimmune signals, stromal niches, interorgan trafficking, adaptive costimulation, interferon brakes, and metabolic/checkpoint programs.
Main caution	ILC2 activation is too broad to be a reusable claim; interpretation should preserve tissue compartment, upstream cue, dominant output, and disease readout.

How to use this page

• Start with Integrated working model and Review map for the fastest orientation.
• Use Major biological branches when the question is disease- or context-specific.
• Use Regulatory architecture when the question is mechanistic.
• Use Interpretation guardrails and Claim-level confidence boundaries before lifting claims into figures, digests, or manuscripts.

Integrated working model

Lung and airway ILC2s are best modeled as tissue-positioned response modules rather than as one fixed type 2 effector population. In one setting they amplify allergic airway disease through IL-5, IL-13, lipid mediators, epithelial alarmins, and memory-like amplification. In another they support epithelial repair, macrophage-niche reprogramming, or tissue homeostasis after respiratory viral injury. Their output is shaped by stromal niches, neuroimmune inputs, metabolism, checkpoint pathways, interferon-mediated brakes, and inflammatory plasticity.

The practical implication is that "ILC2 activation" is not a sufficient biological description. The reusable unit in this wiki is an ILC2 state defined by tissue compartment, upstream cue, dominant output, and disease readout. Selective mouse ILC2-deficiency systems further support the idea that ILC2s can have non-redundant immune functions rather than simply duplicating adaptive Th2 activity, but those findings should still be interpreted within their genetic and tissue-model boundaries (Non-redundant functions of group 2 innate lymphoid cells).

Review map

flowchart TD
    accTitle: ILC2 Review Map
    accDescr: Review-style map of the main pulmonary ILC2 branches in this wiki.

    baseline["Human lung baseline"] --> allergy["Allergic amplification"]
    baseline --> viral["Viral AHR versus repair"]
    baseline --> plasticity["Plasticity / boundary states"]
    allergy --> regulators["Regulatory architecture"]
    viral --> regulators
    plasticity --> regulators
    regulators --> guardrails["Interpretation guardrails"]

    classDef entry fill:#e8f3ff,stroke:#3b6ea8,stroke-width:2px,color:#17324d
    classDef branch fill:#eef7ed,stroke:#4d8a50,stroke-width:2px,color:#173d1d
    classDef mech fill:#fff4de,stroke:#b47a1f,stroke-width:2px,color:#4a3108
    classDef caution fill:#f6eefc,stroke:#7a55a3,stroke-width:2px,color:#2d1645

    class baseline entry
    class allergy,viral,plasticity branch
    class regulators mech
    class guardrails caution

Major biological branches

Human lung baseline

• Human lung baseline: ILC2s are directly detected in human lung tissue using CD45+ Lin- CD127+ CRTH2+ flow-cytometric gating, supporting ILC2 as a true pulmonary entity rather than only a mouse-model construct (Characterization and Quantification of Innate Lymphoid Cell Subsets in Human Lung).

• Epigenetic memory branch: repetitive Alternaria exposure can generate memory-like mouse ILC2s that amplify later subthreshold recall responses, with ATAC-seq and single-cell data supporting distinct repression and preparedness programs rather than simple acute activation (The molecular and epigenetic mechanisms of innate lymphoid cell (ILC) memory and its relevance for asthma).

Allergic amplification and memory-like states

• Allergic amplification: ILC2s respond to IL-33/IL-25, CXCL16, cysteinyl leukotrienes, and allergen experience; allergen-experienced ILC2s can persist as memory-like cells that amplify later allergic lung inflammation (Kinetics of the accumulation of group 2 innate lymphoid cells in IL-33-induced and IL-25-induced murine models of asthma a potential role for the chemokine CXCL16; Lung type 2 innate lymphoid cells express cysteinyl leukotriene receptor 1 which regulates TH2 cytokine production; Allergen-Experienced Group 2 Innate Lymphoid Cells Acquire Memory-like Properties and Enhance Allergic Lung Inflammation).
• Human translational amplification branch: human ILC2s respond strongly to LTE4 and PGD2-linked lipid signaling, while airway eosinophilic asthma can recruit a TL1A/DR3 activation axis and DP2 antagonism can block PGD2-driven migration, aggregation, and cytokine production ex vivo (Cysteinyl leukotriene E4 activates human group 2 innate lymphoid cells and enhances the effect of prostaglandin D2 and epithelial cytokines; The Role of the TL1A/DR3 Axis in the Activation of Group 2 Innate Lymphoid Cells in Subjects with Eosinophilic Asthma; Fevipiprant, a selective prostaglandin D2 receptor 2 antagonist, inhibits human group 2 innate lymphoid cell aggregation and function).

Viral AHR, repair, and macrophage niche effects

• Viral disease bifurcation: influenza can trigger an innate lymphoid IL-33/IL-13 AHR branch, while lung ILCs can also support amphiregulin-mediated epithelial repair after influenza injury. BATF further sharpens the protective wound-healing branch, gammaherpesvirus conditioning shows that ILC2s can reduce type 2 output while instructing monocyte-derived alveolar macrophage identity through GM-CSF, and allergen or IL-33 type 2 inflammation can use ILC2-derived IL-13 to reprogram tissue-resident alveolar macrophages from a PPARgamma-centered homeostatic state toward an IRF4-driven inflammatory niche program (Innate lymphoid cells mediate influenza-induced airway hyper-reactivity independently of adaptive immunity; Innate lymphoid cells promote lung-tissue homeostasis after infection with influenza virus; BATF promotes group 2 innate lymphoid cell-mediated lung tissue protection during acute respiratory virus infection; Dampening type 2 properties of group 2 innate lymphoid cells by a gammaherpesvirus infection reprograms alveolar macrophages; Innate type 2 lymphocytes trigger an inflammatory switch in alveolar macrophages).

Plasticity and noncanonical disease branches

• Plasticity branches: COPD-associated infectious or noxious triggers can convert ILC2s toward an IL-12/IL-18-regulated T-bet+ IFN-gamma+ ILC1-like state; papain/IL-33 plus leukotrienes can drive pathogenic IL-17-producing ST2+ ILC2s; human nasal inflammation shows IL-1beta/IL-23/TGF-beta-driven ILC2-to-IL-17-producing plasticity (Inflammatory triggers associated with exacerbations of COPD orchestrate plasticity of group 2 innate lymphoid cells in the lungs; IL-17-producing ST2(+) group 2 innate lymphoid cells play a pathogenic role in lung inflammation; IL-1beta, IL-23, and TGF-beta drive plasticity of human ILC2s towards IL-17-producing ILCs in nasal inflammation).

• Human severe-asthma sputum boundary state: c-kit+ IL-17A+ intermediate ILC2s are enriched in mixed granulocytic airway inflammation, correlate with neutrophilia, and can be modeled in vitro by IL-1beta plus IL-18 stimulation of sort-purified human ILC2s (A population of c-kit+ IL-17A+ ILC2s in sputum from individuals with severe asthma supports ILC2 to ILC3 trans-differentiation).

• Adaptive costimulation and feedback: IL-33/ST2-activated pulmonary ILC2s can use PD-L1 to promote CD4 T-cell GATA3/IL-13 in mouse helminth-associated type 2 immunity, and ILC2 OX40L can license local Th2/Treg expansion while also supporting a Gata3high Treg feedback circuit that limits effector-memory Th2 expansion. ILC2-derived LIF adds a separate pulmonary lymphatic CCL21/CCR7+ immune-cell egress branch (ILC2s regulate adaptive Th2 cell functions via PD-L1 checkpoint control; Tissue-Restricted Adaptive Type 2 Immunity Is Orchestrated by Expression of the Costimulatory Molecule OX40L on Group 2 Innate Lymphoid Cells; Cross-talk between ILC2 and Gata3high Tregs locally constrains adaptive type 2 immunity; ILC2-derived LIF licences progress from tissue to systemic immunity).

Stromal and airway immune crosstalk

• Stromal/growth-factor regulation: SCF/c-Kit can regulate ILC2 activation and chronic allergic airway disease severity in mouse models, while the separate ILC3 SCF/KIT source should be kept as a neutrophilic asthma branch rather than merged into one universal SCF mechanism (Group 2 innate lymphoid cells (ILC2) are regulated by stem cell factor during chronic asthmatic disease; Pulmonary fibroblast-derived stem cell factor promotes neutrophilic asthma by augmenting IL-17A production from ILC3s).
• Spatial guidance branch: during airway inflammation, activated pulmonary ILC2s aggregate in peribronchial and perivascular regions and use CCR8-CCL8 and matrix cues such as collagen-I to navigate inflamed lung tissue (Pulmonary environmental cues drive group 2 innate lymphoid cell dynamics in mice and humans).
• Human airway crosstalk: induced-sputum asthma data link ILC2s with M2-like macrophage polarization, whereas ILC1/ILC3s align with M1-like macrophage polarization in noneosinophilic asthma contexts (Innate immune crosstalk in asthmatic airways Innate lymphoid cells coordinate polarization of lung macrophages).

Regulatory architecture

Activation and amplification layer

• High confidence: ILC2 allergic lung inflammation is regulated by neuroimmune pathways, including NMU/NMUR1 amplification in mouse allergic inflammation and human allergen-challenge airway ILC2 activation, plus mTORC1-dependent coordination of neuroimmune crosstalk (The neuropeptide NMU amplifies ILC2-driven allergic lung inflammation; Neuromedin-U Mediates Rapid Activation of Airway Group 2 Innate Lymphoid Cells in Mild Asthma; mTORC1 signaling in group 2 innate lymphoid cells coordinates neuro-immune crosstalk in allergic lung inflammation).
• High confidence: lipid-mediator signaling forms a human-relevant activation and inhibition axis in ILC2s, with LTE4 amplifying PGD2 and epithelial-cytokine responses, and fevipiprant blocking PGD2/DP2-driven migration, aggregation, and cytokine production in human ILC2s (Cysteinyl leukotriene E4 activates human group 2 innate lymphoid cells and enhances the effect of prostaglandin D2 and epithelial cytokines; Fevipiprant, a selective prostaglandin D2 receptor 2 antagonist, inhibits human group 2 innate lymphoid cell aggregation and function).

• Medium-high confidence: human airway eosinophilic asthma includes a TL1A/DR3 activation branch, ILC2s also use ICOS:ICOSL costimulatory support for homeostasis and AHR, and activated ILC2s can be positively tuned by CB2 signaling in mouse and humanized systems (ICOS-ligand interaction is required for type 2 innate lymphoid cell function, homeostasis, and induction of airway hyperreactivity; The Role of the TL1A/DR3 Axis in the Activation of Group 2 Innate Lymphoid Cells in Subjects with Eosinophilic Asthma; Cannabinoid receptor 2 engagement promotes group 2 innate lymphoid cell expansion and enhances airway hyperreactivity).

• High confidence: IL-25- or helminth-induced inflammatory ILC2s can move from intestinal tissue to lung through S1P-dependent lymphatic entry and blood circulation in mouse models, adding an interorgan trafficking layer distinct from steady-state tissue residency (S1P-dependent interorgan trafficking of group 2 innate lymphoid cells supports host defense).

Spatial niche and positioning layer

• High confidence: lung ILC2s are spatially organized in adventitial/peribronchovascular niches where fibroblast-like ASCs provide IL-33 and TSLP, and ILC2-derived IL-13 can reciprocally expand or activate the stromal niche (Adventitial Stromal Cells Define Group 2 Innate Lymphoid Cell Tissue Niches).
• High confidence: activated pulmonary ILC2s are dynamically guided within inflamed lung by CCR8-CCL8 localization and extracellular-matrix cues, especially collagen-I-dependent motility programs (Pulmonary environmental cues drive group 2 innate lymphoid cell dynamics in mice and humans).
• Medium-high confidence: airway and alveolar niche consequences are not limited to stromal positioning; in a recent pulmonary type 2 inflammation source, IL-33-activated ILC2-derived IL-13 reprogrammed tissue-resident alveolar macrophages toward an IRF4-driven inflammatory state, linking ILC2 activation to downstream niche restructuring (Innate type 2 lymphocytes trigger an inflammatory switch in alveolar macrophages).

Interferon and checkpoint brakes

• High confidence: IFN-gamma is a direct negative regulator of IL-33-driven ILC2 activation and can restrict ILC2 cytokine output, proliferation, survival, and parenchymal trafficking depending on the model (Interleukin-33 and Interferon-gamma Counter-Regulate Group 2 Innate Lymphoid Cell Activation during Immune Perturbation; Interferon gamma constrains type 2 lymphocyte niche boundaries during mixed inflammation).
• High confidence: during H1N1 influenza in the reported mouse model, IFN-gamma suppresses protective ILC2 IL-5/amphiregulin output without changing viral load, supporting a distinction between ILC2 number and ILC2 function (IFN-gamma increases susceptibility to influenza A infection through suppression of group II innate lymphoid cells).
• High confidence: in allergic airway models, a TLR9-type I IFN-NK cell-IFN-gamma-STAT1 cascade can suppress ILC2-driven AHR, placing microbial sensing upstream of an ILC2 inhibitory checkpoint (Toll-like receptor 9-dependent interferon production prevents group 2 innate lymphoid cell-driven airway hyperreactivity).

Metabolic and state-control layer

• High confidence: ILC2 metabolic and checkpoint programs can either promote or restrain airway inflammation; autophagy preserves activated ILC2 survival and fatty-acid-linked fitness, HIF-1alpha/glycolysis supports ILC2 function, whereas PD-1, dopamine/DRD1, and butyrate constrain ILC2 activation or cytokine output in reported models (Autophagy is critical for group 2 innate lymphoid cell metabolic homeostasis and effector function; Blocking the HIF-1alpha glycolysis axis inhibits allergic airway inflammation by reducing ILC2 metabolism and function; PD-1 pathway regulates ILC2 metabolism and PD-1 agonist treatment ameliorates airway hyperreactivity; Dopamine inhibits group 2 innate lymphoid cell-driven allergic lung inflammation by dampening mitochondrial activity; Regulation of type 2 innate lymphoid cell-dependent airway hyperreactivity by butyrate).
• High confidence: pathogenic airway ILC2 states can also depend on lipid-droplet metabolism, whereas circulating human ILC2s show a distinct OXPHOS-dominant baseline program with glycolysis/mTOR engaged during IL-33-driven activation (Lipid-Droplet Formation Drives Pathogenic Group 2 Innate Lymphoid Cells in Airway Inflammation; Dichotomous metabolic networks govern human ILC2 proliferation and function).
• Medium-high confidence: cholinergic and therapeutic modulation can reshape ILC2-dependent airway inflammation indirectly, as tiotropium reduced papain-driven ILC2/eosinophilic inflammation through a basophil-linked M3R pathway rather than by directly blocking IL-33-stimulated ILC2 cytokine production (Long-acting muscarinic antagonist regulates group 2 innate lymphoid cell-dependent airway eosinophilic inflammation).
• Medium-high confidence: neuroimmune and tissue-maturation axes further diversify ILC2 function; NMU/NMUR1 can induce non-redundant ILC2-derived amphiregulin at barrier surfaces, PAC1/CGRP and beta2-adrenergic signaling can inhibit type 2 inflammation, basophils can prime ILC2s for NMB-mediated inhibition, and mouse lung-gut studies support CCR2/CCR4-linked tissue specialization (beta(2)-adrenergic receptor-mediated negative regulation of group 2 innate lymphoid cell responses; Basophils prime group 2 innate lymphoid cells for neuropeptide-mediated inhibition; Neuropeptide regulation of non-redundant ILC2 responses at barrier surfaces; PAC1 constrains type 2 inflammation through promotion of CGRP signaling in ILC2s; Maturation and specialization of group 2 innate lymphoid cells through the lung-gut axis).
• Medium-high confidence: ILC2s also sit in a broader type 2 tissue circuit that includes epithelial alarmins, stromal border niches, neuroimmune inputs, and adaptive Th2 reinforcement; this framework is useful for interpretation but primary claims should remain source anchored (The ins and outs of innate and adaptive type 2 immunity).
• Medium confidence: extrapulmonary ILC2 regulation includes gut aryl-hydrocarbon-receptor/AHR restraint, RXRgamma lipid-metabolic activation-threshold control, thymic RORalpha lineage commitment, enteric ADM2 tissue-protective neuroimmune signaling, and tuft-cell IL-17RB control of IL-25 bioavailability; these sharpen ILC2 vocabulary but are not direct lung claims (Aryl Hydrocarbon Receptor Signaling Cell Intrinsically Inhibits Intestinal Group 2 Innate Lymphoid Cell Function; Retinoid X receptor gamma dictates the activation threshold of group 2 innate lymphoid cells and limits type 2 inflammation in the small intestine; RORalpha is a critical checkpoint for T cell and ILC2 commitment in the embryonic thymus; CGRP-related neuropeptide adrenomedullin 2 promotes tissue-protective ILC2 responses and limits intestinal inflammation; Tuft cell IL-17RB restrains IL-25 bioavailability and reveals context-dependent ILC2 hypoproliferation).
• High confidence: IL-9/Blimp-1 supports a direct mouse lung allergic-asthma ILC2 identity-fidelity axis, while fungal-infection work adds a pulmonary infection plasticity context in which ILC2s can shift toward ILC3-like states under defined cytokine pressure (IL-9 and Blimp-1 protect the transcriptional identity of group 2 innate lymphocytes in allergic asthma; Innate lymphoid cells integrate sensing and plasticity to control fungal infections).

• High confidence: human severe-asthma induced sputum supports an airway ILC2 clinical-association branch in which GATA3+ and CRTH2+/IL-5+ ILC signatures associate with worse lung function, while anti-IL-5/5Ralpha therapy suppresses IL-5+/IL-13+ airway ILCs without depleting core ILC subset abundance (Severe asthma is characterized by a sex-specific ILC landscape and aberrant airway profile that is suppressed by anti-IL-5/5Ralpha biologics).

• Medium-high confidence: ILC2 asthma output can be restrained by broader immune-regulatory contexts, including hUC-MSC suppression of IL-5/IL-13-producing Th2 and ILC2 responses in severe-asthma model systems and vitamin D3-associated Blimp-1/IL-10 regulatory programs in human and experimental asthma (Mesenchymal Stem Cells Suppress Severe Asthma by Directly Regulating Th2 Cells and Type 2 Innate Lymphoid Cells; Vitamin D3 resolved human and experimental asthma via B lymphocyte-induced maturation protein 1 in T cells and innate lymphoid cells).

Boundary states and noncanonical contexts

• Medium-high confidence: ILC2s participate in noncanonical lung contexts including eosinophil feedback, tumor/NK antagonism, obesity-exacerbated allergic airway disease, silicosis-associated fibroblast/mechanics-driven ILC2-to-ILC1-like plasticity, and tissue-imprinted anticipatory states (Eosinophils promote effector functions of lung group 2 innate lymphoid cells in allergic airway inflammation in mice; ILC2-driven innate immune checkpoint mechanism antagonizes NK cell antimetastatic function in the lung; Innate lymphoid cells contribute to allergic airway disease exacerbation by obesity; Mechanics-activated fibroblasts promote pulmonary group 2 innate lymphoid cell plasticity propelling silicosis progression; Tissue signals imprint ILC2 identity with anticipatory function).
• Medium-high confidence: c-Kit+ CCR6+ ILC2s with ILC3-like IL-17-producing potential should be treated as a boundary-state warning when interpreting IL-17+ ILC populations (c-Kit-positive ILC2s exhibit an ILC3-like signature that may contribute to IL-17-mediated pathologies).

Claim-level confidence boundaries

• High confidence is used for ILC2 claims supported by direct lung or airway evidence linking ILC2 identity to cytokine output, repair activity, airway physiology, macrophage imprinting, or spatial niche behavior.
• Medium-high confidence is used for regulatory and plasticity mechanisms that are experimentally supported but still need tighter lower-lung, human, or disease-general mapping.
• Human nasal, sputum, blood, and lung tissue findings should remain compartment-labeled; they should not be promoted to pan-lung causal claims without matched functional evidence.

Interpretation guardrails

ILC2s should be modeled as lung and airway signal integrators rather than a single fixed type 2 effector cell. In one context they drive IL-5/IL-13 allergic pathology and AHR; in another they support epithelial repair, imprint macrophages, become memory-like, acquire ILC1-like features during COPD-associated inflammation, or enter IL-17-producing boundary states. Entity-level claims should always preserve species, tissue compartment, stimulus, timing, and outcome readout.

Contradiction and supersession

• Pathogenic and protective ILC2 roles are not contradictions unless they are compared in the same disease model, time point, tissue compartment, and perturbation.
• COPD-associated ILC2-to-ILC1-like conversion, allergen-experienced memory-like ILC2s, and IL-17-producing ST2+ ILC2s are distinct plasticity branches.
• Human nasal ILC2-to-IL-17 evidence should not supersede lower-lung or sputum data; keep the tissue label visible. Human sputum intermediate ILC2 evidence should likewise stay compartment-labeled and should not be treated as definitive in vivo lineage tracing.
• SCF/c-Kit effects on ILC2 should be kept separate from fibroblast SCF/KIT effects on ILC3 unless a source directly compares them.

Open questions

• Which ILC2 regulatory axes are conserved between mouse allergic airway models and human asthma phenotypes?
• When do viral infections drive protective wound-healing ILC2 states versus pathogenic type 2 inflammation?
• Are IL-17-producing ST2+ ILC2-like states stable lineages, transient activation states, or mixed-gate artifacts in some settings?
• Which ILC2 mechanisms are actionable in steroid-resistant, neutrophilic, or mixed-granulocytic asthma?

Confidence snapshot

• High confidence: human lung tissue contains identifiable ILC2s within the broader CD45+ Lin- CD127+ pulmonary ILC compartment, giving the entity page a direct human lung anchor beyond mouse models (Characterization and Quantification of Innate Lymphoid Cell Subsets in Human Lung).
• High confidence: ILC2s can drive airway type 2 pathology and AHR in lung/allergy models through IL-33/IL-13 and lipid-mediator pathways, including functional CysLT1R/LTD4 signaling (Innate lymphoid cells mediate influenza-induced airway hyper-reactivity independently of adaptive immunity; Lung type 2 innate lymphoid cells express cysteinyl leukotriene receptor 1 which regulates TH2 cytokine production).
• High confidence: ILC2s can also support lung repair or niche reprogramming after respiratory viral infection through amphiregulin, BATF-linked wound-healing identity, and gammaherpesvirus-conditioned GM-CSF effects on monocyte-derived alveolar macrophages (Innate lymphoid cells promote lung-tissue homeostasis after infection with influenza virus; BATF promotes group 2 innate lymphoid cell-mediated lung tissue protection during acute respiratory virus infection; Dampening type 2 properties of group 2 innate lymphoid cells by a gammaherpesvirus infection reprograms alveolar macrophages).
• High confidence: ILC2 identity and output are plastic in lung or airway disease contexts, including allergen-experienced memory-like ILC2s, COPD-triggered IL-12/IL-18-regulated ILC1-like conversion, and IL-17-producing ST2+ ILC2 states (Allergen-Experienced Group 2 Innate Lymphoid Cells Acquire Memory-like Properties and Enhance Allergic Lung Inflammation; Inflammatory triggers associated with exacerbations of COPD orchestrate plasticity of group 2 innate lymphoid cells in the lungs; IL-17-producing ST2(+) group 2 innate lymphoid cells play a pathogenic role in lung inflammation).
• Medium-high confidence: human nasal inflammation shows IL-1beta/IL-23/TGF-beta-driven ILC2-to-IL-17-producing plasticity, but this should remain labeled as human nasal/airway evidence rather than lower-lung proof (IL-1beta, IL-23, and TGF-beta drive plasticity of human ILC2s towards IL-17-producing ILCs in nasal inflammation).
• Medium-high confidence: SCF/c-Kit regulates ILC2 activation and chronic allergic airway disease severity in mouse models, but SCF/c-Kit also affects other c-Kit+ cell types and should not be framed as ILC2-exclusive without context (Group 2 innate lymphoid cells (ILC2) are regulated by stem cell factor during chronic asthmatic disease).
• Medium-high confidence: activated pulmonary ILC2s are not only niche-positioned but dynamically guided by airway environmental cues, including CCR8-CCL8 localization and collagen-I-dependent motility programs in inflamed lung (Pulmonary environmental cues drive group 2 innate lymphoid cell dynamics in mice and humans).

• Medium-high confidence: ILC2 state is also shaped by costimulatory and metabolic infrastructure, including ICOS:ICOSL support of homeostasis and AHR, autophagy-dependent fatty-acid-linked fitness, and inhibitory neuroimmune branches such as beta2-adrenergic signaling and basophil-primed NMB responsiveness (ICOS-ligand interaction is required for type 2 innate lymphoid cell function, homeostasis, and induction of airway hyperreactivity; Autophagy is critical for group 2 innate lymphoid cell metabolic homeostasis and effector function; beta(2)-adrenergic receptor-mediated negative regulation of group 2 innate lymphoid cell responses; Basophils prime group 2 innate lymphoid cells for neuropeptide-mediated inhibition).

• Medium-high confidence: human severe-asthma sputum provides direct airway evidence for a c-kit+ IL-17A+ intermediate ILC2 state enriched in mixed granulocytic inflammation and associated with IL-1beta/IL-18, but this should be framed as a sputum/airway boundary-state observation rather than in vivo lineage tracing (A population of c-kit+ IL-17A+ ILC2s in sputum from individuals with severe asthma supports ILC2 to ILC3 trans-differentiation).

• Medium-high confidence: ILC2 regulation also includes interorgan trafficking, adaptive costimulation, immune-cell egress control, and epigenetic memory-like preparedness. Mouse sources support S1P-dependent inflammatory ILC2 trafficking to lung, IL-33-induced ILC2 OX40L licensing of local Th2/Treg responses, ILC2-derived LIF control of pulmonary lymphatic egress, and Alternaria-driven memory-like ILC2 programs with distinct chromatin accessibility (S1P-dependent interorgan trafficking of group 2 innate lymphoid cells supports host defense; Tissue-Restricted Adaptive Type 2 Immunity Is Orchestrated by Expression of the Costimulatory Molecule OX40L on Group 2 Innate Lymphoid Cells; ILC2-derived LIF licences progress from tissue to systemic immunity; The molecular and epigenetic mechanisms of innate lymphoid cell (ILC) memory and its relevance for asthma).
• High confidence for the source-specific mouse lung branch: IL-33-induced ILC2 OX40L can license local Th2 and Treg expansion, making ILC2-to-adaptive-immunity costimulation a direct pulmonary mechanism in the current wiki (Tissue-Restricted Adaptive Type 2 Immunity Is Orchestrated by Expression of the Costimulatory Molecule OX40L on Group 2 Innate Lymphoid Cells; ILC Regulation Of Adaptive Immunity).

• High confidence for source-specific mouse lung branches: ILC2 PD-L1 can promote Th2 polarization through T-cell PD-1 in primary helminth-associated type 2 immunity, and ILC2-OX40L can also support Gata3high Treg-mediated restraint of effector-memory Th2 expansion in allergen-driven lung inflammation (ILC2s regulate adaptive Th2 cell functions via PD-L1 checkpoint control; Cross-talk between ILC2 and Gata3high Tregs locally constrains adaptive type 2 immunity).

• Medium confidence: intestinal ILC2s can occupy an IL-10-producing regulatory state, but this is gut-labeled context and should not be treated as default lung ILC2 behavior (ILC2s are the predominant source of intestinal ILC-derived IL-10).

Reading routes

• For disease-first reading, go next to ILC2 roles in pulmonary disease.
• For mechanism-first reading, go next to ILC2 functional regulation mechanisms.

• For adaptive-immunity crosstalk, go next to ILC Regulation Of Adaptive Immunity.

• For cross-subset synthesis, go next to Lung ILC Core Evidence Synthesis.

Related pages

• ILC2 roles in pulmonary disease
• ILC2 functional regulation mechanisms

• ILC Regulation Of Adaptive Immunity

• Lung ILC Disease Roles Companion

• Lung ILC Core Evidence Synthesis
• Reference coverage notes

Future Expansion Directions

This short appendix highlights future literature directions rather than part of the current evidence summary. Literature that would most strengthen this entity page includes:

• Human BAL, bronchial biopsy, sputum, and lung scRNA-seq studies that distinguish resident ILC2s from circulating or nasal ILC2s.
• COPD and smoke-exposure studies that test whether ILC2-to-ILC1-like plasticity occurs in human lung tissue, not only blood or mouse models.
• Perturbation studies separating ILC2 repair, pathogenic type 2 output, memory-like amplification, and IL-17-producing boundary states in the same disease time course.