Type 2 immunity—classically evolved to expel helminths and to repair large-scale tissue injury—centres on the cytokines interleukin (IL)-4, IL-5, IL-9 and IL-13 and on a cellular consortium composed of T-helper-2 (TH2) lymphocytes, group-2 innate lymphoid cells (ILC2s), eosinophils, basophils, mast cells and IgE-class-switched B cells.  These mediators induce alternative (M2) macrophage activation, mucus and antimicrobial peptide secretion, fibroblast proliferation and extracellular-matrix (ECM) deposition, thereby sealing breaches in barrier tissues [1, 2].  Tumours, long portrayed as ‘wounds that do not heal’, frequently express the alarmins IL-33, IL-25 and thymic stromal lymphopoietin (TSLP) downstream of oncogenic RAS-MAPK, β-catenin or hypoxia-inducible pathways, and thus recruit the same type 2 circuits that are indispensable for metazoan repair [3, 4].

I.  Contextual parallels between wound repair and tumour biology
Epithelial stress or necrosis elicits IL-33/IL-25/TSLP release, which activates tissue-resident ILC2s and conditions dendritic cells to polarise TH2 cells.  The downstream effector molecules amphiregulin, arginase-1 and type I/III collagens remodel stroma and restore homeostasis.  In tumours this programme can, depending on spatial and temporal cues, either constrain malignant foci within a fibrotic capsule or generate permissive desmoplasia and aberrant angiogenesis [5, 6].

II.  Tumour-promoting activities of type 2 immunity
1.  ILC2–IL-13–MDSC axis.  Adoptive transfer of pulmonary ILC2s accelerates triple-negative breast-cancer (TNBC) lung metastasis via IL-13–dependent expansion of myeloid-derived suppressor cells (MDSCs); neutralising IL-13 abrogates this effect [7].  A similar IL-25/ILC2 pathway drives immune-suppression in non-small-cell lung cancer (NSCLC) [8] and in cervical carcinoma where IL-33-stimulated ILC2s amplify monocytic MDSCs [9].
2.  Mast-cell orchestration.  In gastric cancer, tumour-derived IL-33 activates ST2+ mast cells that secrete CSF2, CCL3 and IL-6, recruit macrophages and enhance angiogenesis, thereby increasing tumour burden [10].  Mast-cell histamine, tryptase and chymase further liberate pro-angiogenic VEGF and ECM fragments [11].
3.  Fibroblast-driven desmoplasia.  IL-4/IL-13-STAT6 signalling in cancer-associated fibroblasts up-regulates VEGF, CCL2 and CXCL5, fostering vascular sprouting and MDSC infiltration (Naldini et al., 2003).  Excessive collagen cross-linking can create invasion ‘highways’ unless counter-regulated by TGF-β3 (Chang et al., 2014).

III.  Tumour-restraining activities
1.  Eosinophil cytotoxicity and vessel normalisation.  IL-5- or IL-33-expanded eosinophils form CD11b/CD18-dependent immune synapses with tumour cells, release granzyme-B, eosinophil cationic protein and major basic protein, and normalise aberrant vasculature, thereby enhancing CD8+ T-cell infiltration [12, 13].  Extracellular-vesicle cargo from IL-33-activated eosinophils re-programmes tumour cells towards cell-cycle arrest and an epithelial phenotype [14].
2.  ILC2 cross-presentation and adoptive therapy.  Murine and human ILC2s can internalise exogenous antigen, present it on MHC-I and license cytotoxic CD8+ T cells [15].  Adoptive transfer of one IL-33-expanded ILC2 per 60 tumour cells is sufficient to curb metastasis and outperforms CAR-T cells on a per-cell basis [16].  
3.  TH2-IL-5-eosinophil circuit.  Transfer of ex vivo–polarised TH2 cells or recombinant IL-5 inhibits colorectal and pancreatic tumours by recruiting eosinophils and repolarising macrophages [17].
4.  Conditional mast-cell immunity.  When ligated by tumour-specific IgE, FcεRI+ mast cells release TNF-α and leukotrienes that enhance antigen uptake by dendritic cells and promote CD8 activation [18].  IgE antibodies against melanoma-associated antigens have shown superior antibody-dependent cytotoxicity relative to IgG [19].

IV.  Modular mechanisms within the tumour micro-environment
•  Cytolytic effector function: native eosinophil degranulation, IgE-armed mast cells and CAR-engineered ILC2s targeting IL-13Rα2 exhibit direct lysis of glioblastoma [20].
•  Stromal containment versus permissive fibrosis: early IL-4/IL-13 signalling can entrap indolent lesions in collagenous cages, whereas persistent activation, together with galectin-mediated ECM cross-linking, facilitates invasion [21].
•  Angiogenesis versus normalisation: TH2 cytokines and mast-cell VEGF promote sprouting (Naldini et al., 2003), while activated eosinophils secrete chemokines (CXCL9/10) that attract type 1 effectors and induce pericyte coverage, restoring perfusion (Carretero et al., 2015).
•  Immune regulation: IL-4/IL-13 up-regulate PD-L2, whereas IL-33 induces PD-1 on ILC2s; blockade of PD-1 restores ILC2 activity [22, 23].

V.  Crosstalk with immune-checkpoint blockade (ICB)
Baseline peripheral eosinophil counts of 100–500 cells µL⁻¹ predict longer overall survival in ICI-treated NSCLC [24].  Dynamic increases in relative eosinophil counts within four to six weeks correlate with disease control and, paradoxically, with immune-related adverse events [25, 26].  Conversely, elevated soluble PD-1/PD-L1—inducible by IL-4/IL-13—marks primary resistance [27].  Dual blockade of IL-33 and PD-L1 re-programmes the micro-environment, depletes suppressive ILC2 subsets and restores CD8 effector function [28].  Exogenous IL-33 synergises with anti-PD-1 to awaken quiescent nILC2s and enhance cytotoxic immunity [29].

VI.  Parasitic helminths: carcinogenic risks and immunological paradoxes
Schistosoma haematobium and Opisthorchis viverrini chronically drive IL-13-mediated fibrosis and nitrosamine production, predisposing to bladder and cholangiocarcinoma [30, 31].  Yet, helminth-induced systemic TH2/regulatory bias can dampen chronic TH1 inflammation, yielding reduced incidence of colorectal and breast cancer in endemic regions [32].  The Taenia-derived peptide GK-1 diminishes PD-1/PD-L1 expression and potentiates anti-melanoma CD8 responses in mice [33].  Vigilance is required when deploying IL-5 agonists or ILC2-based therapies in helminth-endemic settings to avoid eosinophil-driven pathology.

VII.  Translational strategies and combination approaches
•  Cytokine and receptor blockade: Dupilumab (anti-IL-4Rα) and IL-13Rα1/2 antibodies are entering oncology trials; IL-4Rα-lytic hybrid peptides eradicate IL-4Rα-high pancreatic xenografts [34].  IL-4 neutralisation augments CpG or anti-OX40 immunotherapies in murine models [35].
•  Targeting IL-13Rα2: next-generation immunotoxins, vaccines and CAR-T cells against IL-13Rα2 show activity in glioblastoma; bispecific IL-13Rα2/TGF-β CAR-T cells overcome TGF-β-mediated suppression (Hou et al., 2024).  Humanised IL-13Rα2 CAR-T cells gain further potency when combined with CTLA-4 blockade [36].
•  ILC2 adoptive therapy: IL-33-expanded or CAR-engineered ILC2s provide high per-cell efficacy and can be paired with PD-1 blockade to forestall exhaustion.
•  Eosinophil-mobilising adjuvants: pegylated IL-5 or DPP4 inhibitors (which elevate CCL11) synergise with ICB by recruiting cytotoxic eosinophils [37].

VIII.  Priority research questions
1.  Which molecular checkpoints dictate the switch from fibrosis-mediated containment to invasion in IL-4/IL-13-rich tumours?
2.  Can single-cell and spatial transcriptomics resolve functional heterogeneity of tumour-resident ILC2s and predict responsiveness to ICB?
3.  What are the oncological consequences of chronic IL-4Rα blockade (e.g., dupilumab) in patients with atopic disease?
4.  How do helminth co-infections modulate pharmacokinetics, toxicity and efficacy of ICB in endemic populations?
5.  Is eosinophil degranulation a driver of immune-related adverse events, and can selective Siglec-8 blockade mitigate toxicity without compromising anti-tumour efficacy?

IX.  Limitations
Much mechanistic knowledge derives from murine models featuring supra-physiologic cytokine expression or germline deletions; human tumours exhibit greater cellular and stromal complexity.  Biomarker studies linking eosinophils or serum IL-4/IL-13 to ICB outcomes remain retrospective and confounded by corticosteroid use, infection or atopy.  Prospective trials incorporating multi-omic profiling and controlled sampling intervals are required.

Conclusion
Type 2 immunity is a biological ‘double-edged sword’.  Its default remit—repairing injured tissues while containing collateral damage—can be hijacked by tumours to sculpt an immunosuppressive, desmoplastic niche.  Yet the same eosinophils, ILC2s, TH2 cells and IgE-armed mast cells harbour latent cytotoxic and vessel-normalising capabilities that can be unleashed with precision engineering.  A nuanced understanding of the spatiotemporal cues that toggle type 2 programmes will allow clinicians to convert this response from tumour ally to foe, broadening the therapeutic arsenal of combination immunotherapy.

References
----------
[1] Thomas A Wynn, Thirumalai R Ramalingam (2012). Mechanisms of fibrosis: therapeutic translation for fibrotic disease.. PMID: 22772564.
[2] PMID: 26885856. Reference details unavailable.
[3] Melanie Bruchard, Francois Ghiringhelli (2019). Deciphering the Roles of Innate Lymphoid Cells in Cancer.. PMID: 31024531.
[4] A Naldini, A Pucci, C Bernini, F Carraro (2003). Regulation of angiogenesis by Th1- and Th2-type cytokines.. PMID: 12570799.
[5] Kenneth M Adusei, Tran B Ngo, Kaitlyn Sadtler (2021). T lymphocytes as critical mediators in tissue regeneration, fibrosis, and the foreign body response.. PMID: 33905946.
[6] Zhen Chang, Yo Kishimoto, Ayesha Hasan, Nathan V Welham (2014). TGF-β3 modulates the inflammatory environment and reduces scar formation following vocal fold mucosal injury in rats.. PMID: 24092879.
[7] Na Zhao, Wenwen Zhu, Jia Wang, Weiwei Liu, Longdan Kang, Rui Yu, Beixing Liu (2021). Group 2 innate lymphoid cells promote TNBC lung metastasis via the IL-13-MDSC axis in a murine tumor model.. PMID: 34217145.
[8] Ilham Bahhar, Zeynep Eş, Oğuzhan Köse, Akif Turna, Mehmet Zeki Günlüoğlu, Aslı Çakır, Deniz Duralı, Fay C Magnusson (2023). The IL-25/ILC2 axis promotes lung cancer with a concomitant accumulation of immune-suppressive cells in tumors in humans and mice.. PMID: 37781372.
[9] Bihui Wang, Yuejie Zhu, Yulian Zhang, Zhenyu Ru, Liqiao Chen, Manli Zhang, Yufeng Wu, Jianbing Ding, Zhifang Chen (2025). Hyperactivity of the IL-33-ILC2s-IL-13-M-MDSCs axis promotes cervical cancer progression.. PMID: 39615114.
[10] Moritz F Eissmann, Christine Dijkstra, Andrew Jarnicki, Toby Phesse, Jamina Brunnberg, Ashleigh R Poh, Nima Etemadi, Evelyn Tsantikos, Stefan Thiem, Nicholas D Huntington, Margaret L Hibbs, Alex Boussioutas, Michele A Grimbaldeston, Michael Buchert, Robert J J O'Donoghue, Frederick Masson, Matthias Ernst (2019). IL-33-mediated mast cell activation promotes gastric cancer through macrophage mobilization.. PMID: 31227713.
[11] Grzegorz Dyduch, Karolina Kaczmarczyk, Krzysztof Okoń (2012). Mast cells and cancer: enemies or allies?. PMID: 22535614.
[12] Rafael Carretero, Ibrahim M Sektioglu, Natalio Garbi, Oscar C Salgado, Philipp Beckhove, Günter J Hämmerling (2015). Eosinophils orchestrate cancer rejection by normalizing tumor vessels and enhancing infiltration of CD8(+) T cells.. PMID: 25915731.
[13] Sara Andreone, Francesca Spadaro, Carla Buccione, Jacopo Mancini, Antonella Tinari, Paola Sestili, Adriana Rosa Gambardella, Valeria Lucarini, Giovanna Ziccheddu, Isabella Parolini, Cristiana Zanetti, Maria Teresa D'Urso, Adele De Ninno, Luca Businaro, Claudia Afferni, Fabrizio Mattei, Giovanna Schiavoni (2019). IL-33 Promotes CD11b/CD18-Mediated Adhesion of Eosinophils to Cancer Cells and Synapse-Polarized Degranulation Leading to Tumor Cell Killing.. PMID: 31717819.
[14] Adriana Rosa Gambardella, Caterina Antonucci, Cristiana Zanetti, Francesco Noto, Sara Andreone, Davide Vacca, Valentina Pellerito, Chiara Sicignano, Giuseppe Parrottino, Valentina Tirelli, Antonella Tinari, Mario Falchi, Adele De Ninno, Luca Businaro, Stefania Loffredo, Gilda Varricchi, Claudio Tripodo, Claudia Afferni, Isabella Parolini, Fabrizio Mattei, Giovanna Schiavoni (2024). IL-33 stimulates the anticancer activities of eosinophils through extracellular vesicle-driven reprogramming of tumor cells.. PMID: 39061080.
[15] Jihyun Kim, Seung Geun Song, Suhyun Park, Young Gyun Ko, Jongho Ham, TaeSoo Kim, Sang-Jun Ha, Yong-Soo Bae, Doo Hyun Chung, Hye Young Kim (2025). Antigen Cross-Presentation by Type-2 Innate Lymphoid Cells Facilitates the Activation of Anti-Tumor CD8+ T Cells.. PMID: 40245114.
[16] Iryna Saranchova, Clara Wenjing Xia, Stephanie Besoiu, Pablo L Finkel, Samantha L S Ellis, Suresh Kari, Lonna Munro, Cheryl G Pfeifer, Ladan Fazli, Martin E Gleave, Wilfred A Jefferies (2024). A novel type-2 innate lymphoid cell-based immunotherapy for cancer.. PMID: 38524132.
[17] Damian Jacenik, Ioannis Karagiannidis, Ellen J Beswick (2023). Th2 cells inhibit growth of colon and pancreas cancers by promoting anti-tumorigenic responses from macrophages and eosinophils.. PMID: 36376448.
[18] Barbara Platzer, Kutlu G Elpek, Viviana Cremasco, Kristi Baker, Madeleine M Stout, Cornelia Schultz, Eleonora Dehlink, Kai-Ting C Shade, Robert M Anthony, Richard S Blumberg, Shannon J Turley, Edda Fiebiger (2015). IgE/FcεRI-Mediated Antigen Cross-Presentation by Dendritic Cells Enhances Anti-Tumor Immune Responses.. PMID: 25753415.
[19] Jitesh Chauhan, Melanie Grandits, Lais C G F Palhares, Silvia Mele, Mano Nakamura, Jacobo López-Abente, Silvia Crescioli, Roman Laddach, Pablo Romero-Clavijo, Anthony Cheung, Chara Stavraka, Alicia M Chenoweth, Heng Sheng Sow, Giulia Chiaruttini, Amy E Gilbert, Tihomir Dodev, Alexander Koers, Giulia Pellizzari, Kristina M Ilieva, Francis Man, Niwa Ali, Carl Hobbs, Sara Lombardi, Daniël A Lionarons, Hannah J Gould, Andrew J Beavil, Jenny L C Geh, Alastair D MacKenzie Ross, Ciaran Healy, Eduardo Calonje, Julian Downward, Frank O Nestle, Sophia Tsoka, Debra H Josephs, Philip J Blower, Panagiotis Karagiannis, Katie E Lacy, James Spicer, Sophia N Karagiannis, Heather J Bax (2023). Anti-cancer pro-inflammatory effects of an IgE antibody targeting the melanoma-associated antigen chondroitin sulfate proteoglycan 4.. PMID: 37185332.
[20] Andrew J Hou, Ryan M Shih, Benjamin R Uy, Amanda Shafer, ZeNan L Chang, Begonya Comin-Anduix, Miriam Guemes, Zoran Galic, Su Phyu, Hideho Okada, Katie B Grausam, Joshua J Breunig, Christine E Brown, David A Nathanson, Robert M Prins, Yvonne Y Chen (2024). IL-13Rα2/TGF-β bispecific CAR-T cells counter TGF-β-mediated immune suppression and potentiate anti-tumor responses in glioblastoma.. PMID: 38982561.
[21] Dong Yu, Ming Bu, Ping Yu, Yaping Li, Yang Chong (2022). Regulation of wound healing and fibrosis by galectins.. PMID: 35589840.
[22] Chaoyun Yin, Yani Pa, Guangyu Li, Qiang Chen, Xizu Wang, Xijun He, Huangao Zhou (2024). Tumor cells inhibit the activation of ILC2s through up-regulating PD-1 expression.. PMID: 38678437.
[23] Hongshen Niu, Huasheng Zhang, Dongdi Wang, Linfeng Zhao, Youqin Zhang, Wenyong Zhou, Jingjing Zhang, Xiaohui Su, Jiping Sun, Bing Su, Ju Qiu, Lei Shen (2024). LKB1 prevents ILC2 exhaustion to enhance antitumor immunity.. PMID: 38670109.
[24] Eiji Takeuchi, Kensuke Kondo, Yoshio Okano, Seiya Ichihara, Michihiro Kunishige, Naoki Kadota, Hisanori Machida, Nobuo Hatakeyama, Keishi Naruse, Hirokazu Ogino, Hiroshi Nokihara, Tsutomu Shinohara, Yasuhiko Nishioka (2023). Pretreatment eosinophil counts as a predictive biomarker in non-small cell lung cancer patients treated with immune checkpoint inhibitors.. PMID: 37669914.
[25] Hiroyuki Ohashi, Sora Takeuchi, Tomomitsu Miyagaki, Takafumi Kadono (2020). Increase of lymphocytes and eosinophils, and decrease of neutrophils at an early stage of anti-PD-1 antibody treatment is a favorable sign for advanced malignant melanoma.. PMID: 32595179.
[26] Eiji Takeuchi, Hirokazu Ogino, Kensuke Kondo, Yoshio Okano, Seiya Ichihara, Michihiro Kunishige, Naoki Kadota, Hisanori Machida, Nobuo Hatakeyama, Keishi Naruse, Hiroshi Nokihara, Tsutomu Shinohara, Yasuhiko Nishioka (2024). An increased relative eosinophil count as a predictive dynamic biomarker in non-small cell lung cancer patients treated with immune checkpoint inhibitors.. PMID: 38087769.
[27] S Ugurel, D Schadendorf, K Horny, A Sucker, S Schramm, J Utikal, C Pföhler, R Herbst, B Schilling, C Blank, J C Becker, A Paschen, L Zimmer, E Livingstone, P A Horn, V Rebmann (2020). Elevated baseline serum PD-1 or PD-L1 predicts poor outcome of PD-1 inhibition therapy in metastatic melanoma.. PMID: 31912789.
[28] Yanyang Nan, Yu Bai, Xiaozhi Hu, Kaicheng Zhou, Tao Wu, An Zhu, Mengyang Li, Zihan Dou, Zhonglian Cao, Xumeng Zhang, Shuwen Xu, Yuanzhen Zhang, Jun Lin, Xian Zeng, Jiajun Fan, Xuyao Zhang, Xuebin Wang, Dianwen Ju (2024). Targeting IL-33 reprograms the tumor microenvironment and potentiates antitumor response to anti-PD-L1 immunotherapy.. PMID: 39231544.
[29] Jiawei Yue, Hui Guo, Peng Xu, Jinhong Ma, Weifeng Shi, Yumin Wu (2024). Combination of IL-33 with PD-1 blockade augment mILC2s-mediated anti-tumor immunity.. PMID: 38430390.
[30] Naina Arora, Rimanpreet Kaur, Farhan Anjum, Shweta Tripathi, Amit Mishra, Rajiv Kumar, Amit Prasad (2019). Neglected Agent Eminent Disease: Linking Human Helminthic Infection, Inflammation, and Malignancy.. PMID: 31867284.
[31] Sidhant Jain, Meenakshi Rana (2023). From the discovery of helminths to the discovery of their carcinogenic potential.. PMID: 38095695.
[32] Katerina Oikonomopoulou, Davor Brinc, Andreas Hadjisavvas, Georgios Christofi, Kyriacos Kyriacou, Eleftherios P Diamandis (2014). The bifacial role of helminths in cancer: involvement of immune and non-immune mechanisms.. PMID: 24588712.
[33] Noé Rodríguez-Rodríguez, Iris K Madera-Salcedo, Emmanuel Bugarin-Estrada, Elizabeth Sánchez-Miranda, Diana Torres-García, Jacquelynne Cervantes-Torres, Gladis Fragoso, Florencia Rosetti, José C Crispín, Edda Sciutto (2020). The helminth-derived peptide GK-1 induces an anti-tumoral CD8 T cell response associated with downregulation of the PD-1/PD-L1 pathway.. PMID: 31299381.
[34] Liying Yang, Tomohisa Horibe, Masayuki Kohno, Mari Haramoto, Koji Ohara, Raj K Puri, Koji Kawakami (2012). Targeting interleukin-4 receptor α with hybrid peptide for effective cancer therapy.. PMID: 22084165.
[35] Shuku-Ei Ito, Hidekazu Shirota, Yuki Kasahara, Ken Saijo, Chikashi Ishioka (2017). IL-4 blockade alters the tumor microenvironment and augments the response to cancer immunotherapy in a mouse model.. PMID: 28733709.
[36] Yibo Yin, Alina C Boesteanu, Zev A Binder, Chong Xu, Reiss A Reid, Jesse L Rodriguez, Danielle R Cook, Radhika Thokala, Kristin Blouch, Bevin McGettigan-Croce, Logan Zhang, Christoph Konradt, Alexandria P Cogdill, M Kazim Panjwani, Shuguang Jiang, Denis Migliorini, Nadia Dahmane, Avery D Posey, Carl H June, Nicola J Mason, Zhiguo Lin, Donald M O'Rourke, Laura A Johnson (2018). Checkpoint Blockade Reverses Anergy in IL-13Rα2 Humanized scFv-Based CAR T Cells to Treat Murine and Canine Gliomas.. PMID: 30306125.
[37] Clémence Hollande, Jeremy Boussier, James Ziai, Tamaki Nozawa, Vincent Bondet, Wilson Phung, Binfeng Lu, Darragh Duffy, Valerie Paradis, Vincent Mallet, Gérard Eberl, Wendy Sandoval, Jill M Schartner, Stanislas Pol, Rosa Barreira da Silva, Matthew L Albert (2019). Inhibition of the dipeptidyl peptidase DPP4 (CD26) reveals IL-33-dependent eosinophil-mediated control of tumor growth.. PMID: 30778250.