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ILC2s regulate adaptive Th2 cell functions via PD-L1 checkpoint control

Citation

  • Verified title: ILC2s regulate adaptive Th2 cell functions via PD-L1 checkpoint control
  • Authors: Christian Schwartz, Adnan R. Khan, Achilleas Floudas, Sean P. Saunders, Emily Hams, Hans-Reimer Rodewald, Andrew N. J. McKenzie, and Padraic G. Fallon
  • Journal/article marker: Journal of Experimental Medicine 214(9):2507-2521
  • Publication year: 2017
  • DOI: 10.1084/jem.20170051
  • Metadata source: source PDF first page and DOI line in extracted text

Ingest Mode

  • Mode: focused manual crystallization mode
  • Meaning: this note is a source-reviewed evidence note. It may support topic/entity/digest synthesis when species, tissue, perturbation, and assay context are preserved.

Source Type

  • primary mouse mechanistic study with lung ILC2, CD4 T-cell, helminth-infection, papain-inflammation, in vitro coculture, adoptive-transfer, and conditional-deletion evidence
  • Main cell focus: pulmonary ILC2s and CD4 Th2 cells
  • Main context: mouse lung type 2 immunity during Nippostrongylus brasiliensis infection, with papain lung-inflammation support for PD-L1 induction
  • Knowledge note status: source-reviewed evidence note suitable for ILC2-adaptive-immunity and ILC2 checkpoint/costimulation framing.

Evidence Profile

  • Overall confidence: high for source-specific mouse evidence that activated pulmonary ILC2s upregulate PD-L1 and use PD-L1:PD-1 signaling to promote GATA3 and type 2 cytokine programs in CD4 T cells.
  • Evidence tags: #source/primary #species/mouse #tissue/lung #tissue/gut #cell/ILC2 #cell/T_cell #assay/flow #assay/in_vivo #assay/in_vitro #assay/KO #outcome/infection #outcome/inflammation #axis/adaptive_immunity #axis/ILC_regulation #axis/checkpoint #status/focused_crystallization
  • Primary biological axis: IL-33/ST2-activated lung ILC2s upregulate PD-L1, engage PD-1 on CD4 T cells, and promote early Th2 polarization during primary helminth-associated type 2 immunity.

Why It Matters Here

This source adds a direct lung ILC2-to-CD4 T-cell checkpoint mechanism. It is especially useful because PD-L1 behaves as an activating costimulatory signal for Th2 polarization in this type 2 context, rather than as a simple inhibitory immune-checkpoint label.

Key Findings

  • Lung ILC2s upregulated PD-L1, but not PD-L2, after N. brasiliensis infection; PD-L1 expression peaked around the early lung ILC2 response and was also observed after papain-induced lung inflammation.
  • PD-L1 induction on ILC2s was driven by IL-33/ST2-linked activation and did not require T cells or MHCII-dependent adaptive contact.
  • Global PD-L1 deficiency delayed worm expulsion and reduced intestinal goblet-cell/mucus responses, but did not impair ILC2 expansion or intrinsic ILC2 IL-4/IL-5/IL-13 production.
  • In ILC2-CD4 T-cell coculture, PD-L1-expressing ILC2s promoted CD4 T-cell GATA3 expression and IL-13 production; this required PD-1 on CD4 T cells and direct cell contact.
  • Recombinant PD-L1-Fc increased GATA3 in naive CD4 T cells in a PD-1-dependent and IL-4Ralpha-independent manner, supporting a direct checkpoint signal toward Th2 polarization.
  • Adoptive transfer and conditional Cd274 deletion in ILC-lineage systems showed that ILC2 PD-L1 was required for optimal lung CD4 T-cell GATA3, IL-5/IL-13 output, eosinophil recruitment, and worm expulsion during primary infection.

Claim-Level Confidence

  • High confidence: in the reported mouse helminth model, activated pulmonary ILC2s use PD-L1:PD-1 signaling to promote adaptive Th2 polarization.
  • High confidence: PD-L1 in this source should be interpreted as a context-dependent costimulatory checkpoint for Th2 differentiation, not as a universal inhibitory checkpoint.
  • Medium-high confidence: papain data support PD-L1 induction on ILC2s during allergic-type lung inflammation, but the strongest functional evidence is in the N. brasiliensis infection system.
  • Low confidence: this source should not be used as direct proof of the same pathway in human asthma, checkpoint-inhibitor pneumonitis, or chronic allergic disease without matched human or disease-specific evidence.

Methods and Context

  • Species/context: mouse C57BL/6-centered models with N. brasiliensis primary infection, papain lung inflammation, IL-33/IL-25 cytokine administration, and conditional genetic perturbation.
  • Main compartments: lung for ILC2 and CD4 T-cell interaction; small intestine for worm-burden and mucus/goblet-cell outcome after helminth migration.
  • Main assays: flow cytometry, intracellular cytokine staining, ILC2 and CD4 T-cell sorting, coculture, Transwell testing, recombinant PD-L1-Fc stimulation, adoptive transfer into Rag2-/- Il2rg-/- mice, and Cd274 conditional deletion using IL7Ralpha-Cre and inducible Id2-CreERT2.
  • Best wiki use: lung ILC2 regulation of adaptive Th2 immunity, PD-L1:PD-1 costimulatory checkpoint, and species/model-labeled type 2 immunity.

Caveats

  • The main in vivo functional model is primary helminth infection, not human asthma.
  • Lung ILC2-PD-L1 effects on Th2 polarization were linked to intestinal worm expulsion, but the authors note that how pulmonary interactions translate into intestinal clearance remains incompletely resolved.
  • IL7Ralpha-Cre can affect more than mature ILC2s; the inducible Id2-CreERT2 experiment helps narrow attribution to the ILC lineage.
  • PD-1 also has ILC2-intrinsic inhibitory roles in other sources, so PD-1/PD-L1 biology should be described by cellular direction: ILC2 PD-L1 acting on T-cell PD-1 is not the same as PD-1 signaling inside ILC2s.

Contradiction and Supersession

  • Contradiction status: this source explains why PD-L1 can promote rather than suppress adaptive type 2 immunity in a type 2 cytokine context.
  • Supersession status: complements OX40L and ICOS/ICOSL ILC2 costimulation sources; it does not replace them because the adaptive target and outcome are distinct.

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