Immune Signal IL-18 Supercharges Rare T Cells for Solid Tumor Therapy

A rare but powerful population of immune cells may finally be ready for its manufacturing breakthrough. In a study published in the Journal of Translational Medicine, researchers in China report that adding the inflammatory signaling molecule interleukin-18, or IL-18, to laboratory cultures of human Vδ1 T cells dramatically improves how many of these cells can be grown and how well they perform once inside a tumor-bearing body. The finding addresses one of the most stubborn bottlenecks in bringing gamma-delta T cell therapies to patients with solid tumors: these cells are extraordinarily scarce in the bloodstream, and the handful that can be harvested from a typical blood draw have been difficult to expand into the billions of cells required for a clinically meaningful dose.

Vδ1 T cells belong to the gamma-delta T cell family, a small subset of lymphocytes that carry an unconventional T cell receptor built from delta and gamma chains rather than the familiar alpha and beta chains found on most T cells. What makes them attractive for cancer immunotherapy is their recognition strategy. Unlike conventional T cells, which scan cells for peptide fragments presented on major histocompatibility complex molecules, Vδ1 T cells detect stress-associated ligands and other danger signals that appear on the surface of transformed and infected cells. This MHC-independent recognition means that donor-derived Vδ1 T cells can, in principle, be infused into unrelated recipients without the severe rejection risks and graft-versus-host complications that complicate other allogeneic cell therapies. Their natural tendency to home into tissues adds a further advantage for attacking solid tumors, which are notoriously difficult for circulating immune cells to infiltrate.

Yet the same rarity that makes Vδ1 T cells immunologically convenient also makes them logistically challenging. They typically account for only a small fraction of the lymphocytes circulating in peripheral blood, so isolating enough of them for manufacturing has been a persistent obstacle. The research team, led by Shuntian Chen, Lujie Zhao, Xinrui Xie, Haoyuan Wu and senior author Hongling Wu, with institutions including the Guangzhou Institute of Respiratory Health at Guangzhou Medical University and the Guangzhou Institutes of Biomedicine and Health of the Chinese Academy of Sciences, set out to determine whether IL-18, a cytokine already known to shape the behavior of conventional T cells and natural killer cells, could unlock the proliferative potential of Vδ1 T cells as well.

The experimental design was straightforward but systematic. The researchers isolated primary human Vδ1 T cells from donor blood using magnetic bead separation and cultured them with antibodies against CD3, a coreceptor that provides T cells with an activation signal, together with interleukin-15, a growth factor widely used to drive the expansion of innate-like lymphocytes. Some cultures received IL-18 in addition; others did not. The team then tracked how fast the cells divided, what surface molecules they displayed, and how long they survived, using flow cytometry to quantify each of these parameters across the culture period.

The results on proliferation were striking. IL-18 significantly accelerated cell-cycle progression, pushing the Vδ1 T cells into division more rapidly and sustaining robust clonal expansion over the course of the culture. Crucially, this growth did not come at the cost of purity: the expanded populations retained a high proportion of genuine Vδ1 T cells, an important consideration for any manufacturing process in which overgrowth of contaminating cell types can render a product unusable. For a cell type whose scarcity has been the primary barrier to clinical translation, the ability to generate large, clean batches from a modest starting population represents a substantial advance in manufacturability.

Expansion alone, however, is not enough. Cells grown in the laboratory must remain functional when they encounter the hostile environment of a tumor, where nutrient deprivation, hypoxia and immunosuppressive signals conspire to exhaust or kill infiltrating lymphocytes. Here too, IL-18 left a measurable imprint. The cytokine-treated Vδ1 T cells showed enhanced survival during prolonged exposure to tumor cells, suggesting that IL-18 conditioning confers a degree of resistance to the apoptotic pressures of the tumor microenvironment. They also produced greater quantities of inflammatory cytokines, including interferon-gamma and tumor necrosis factor alpha, which can recruit and activate other arms of the immune response, and they migrated more effectively toward tumor-derived signals in directed migration assays.

One result complicates the otherwise rosy picture and reveals something important about how IL-18 reshapes these cells. In short-term laboratory killing assays, the IL-18-expanded Vδ1 T cells actually showed reduced contact-dependent cytotoxicity, meaning they were somewhat less efficient at directly killing tumor cells through cell-to-cell contact. This apparent deficit, however, did not translate into weaker antitumor activity in living animals. The researchers turned to RNA sequencing and quantitative PCR to probe the transcriptional shifts underlying these changes, finding alterations in gene programs associated with cell survival, inflammatory signaling and apoptosis regulation, including changes in genes such as BAX, a pro-apoptotic regulator, and death receptor pathway components. The molecular profile suggested that IL-18 redirects the cells away from a purely cytotoxic specialization and toward a more durable, inflammation-oriented and tissue-infiltrating state.

The decisive test came in an animal model. The team used mice bearing xenografts of A549 cells, a human lung carcinoma line derived from a non-small cell lung cancer, and compared the therapeutic effects of IL-18-conditioned Vδ1 T cells against control Vδ1 T cells expanded without the cytokine. Bioluminescence imaging was used to track tumor burden over time. The IL-18-expanded cells suppressed tumor growth more effectively and, most importantly, significantly prolonged the survival of the tumor-bearing mice. The in vivo superiority of the IL-18-conditioned product, despite its reduced immediate killing capacity in vitro, underscores a recurring lesson in cell therapy development: laboratory killing assays do not always predict therapeutic performance, and properties such as persistence, migration and cytokine output can matter more for solid tumor control than raw cytotoxicity measured over a few hours in a culture dish.

The translational implications are considerable. Because Vδ1 T cells can be used in an allogeneic, off-the-shelf format, an optimized expansion protocol could enable the production of standardized cell products from healthy donors, manufactured in advance and administered to many patients without the individualized engineering timelines required for autologous therapies such as CAR-T cells. The study also did not involve clinical research on human subjects; all animal work was approved by the Institutional Animal Care and Use Committee of the Guangzhou Institutes of Biomedicine and Health, and the findings remain at the preclinical stage. Moving from xenograft models to human trials will require demonstrating safety, dosing feasibility and efficacy in patients, and the authors note that the work was supported by the National Natural Science Foundation of China and the National Key Research and Development Program of China.

For the broader field of gamma-delta T cell immunotherapy, the study adds IL-18 to the toolkit of cytokines that can be deployed to tune cell products for specific therapeutic goals. Interleukin-15 has long served as the workhorse expansion factor for innate-like lymphocytes, but IL-18 appears to impart a complementary identity, one that favors longevity, inflammatory potency and tumor homing over immediate cytolytic function. As researchers continue to engineer gamma-delta T cells with chimeric antigen receptors and other enhancements, the ability to shape their baseline fitness through cytokine conditioning could prove essential. If the results hold up in clinical testing, a simple change to the culture recipe, the addition of a single signaling molecule, may help transform a scarce circulating curiosity into a scalable weapon against some of the hardest tumors to treat.

Subject of Research: IL-18-driven expansion and functional enhancement of human Vδ1 gamma-delta T cells for solid tumor immunotherapy

Article Title: IL‑18 improves the expansion and functional fitness of human Vδ1 T cells for superior solid tumor immunotherapy

Article References: IL‑18 improves the expansion and functional fitness of human Vδ1 T cells for superior solid tumor immunotherapy. (n.d.). https://doi.org/10.1186/s12967-026-09079-w

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09079-w

Keywords: Vδ1 T cells, gamma-delta T cells, IL-18, interleukin-15, immunotherapy, solid tumors, lung cancer, adoptive cell therapy, cytokines, tumor microenvironment, allogeneic cell therapy, preclinical study