Rival immune messengers turn out to be secret partners in healing

For decades, immunologists have framed the conversation between inflammatory and anti-inflammatory cytokines as a tug-of-war. Proinflammatory signals such as tumor necrosis factor, or TNF, drive the fiery, tissue-destroying side of immunity, while interleukin-4, or IL-4, is celebrated as a calming influence that steers immune cells toward repair and resolution. A new study published in Nature Communications by Ruoxi Yuan, Chao Yang, Bikash Mishra, David Oliver, Richard D. Bell, Lionel B. Ivashkiv and colleagues at the Hospital for Special Surgery and Weill Cornell Medicine upends that tidy narrative. Working in primary human monocytes and in a skin wound-healing model, the researchers found that TNF does not simply oppose IL-4. Instead, it acts mainly as a costimulator that amplifies the IL-4-driven gene expression program, while IL-4, in turn, selectively suppresses only one arm of the TNF response.

The central surprise of the study lies in the asymmetry of this crosstalk. When the team exposed human monocytes and macrophages to TNF and IL-4 together, they expected the classic pattern of mutual cross-inhibition that has dominated the literature on antagonistic cytokine pairs. What they observed instead was cooperation. TNF functioned predominantly as a partner that expanded and intensified the set of genes switched on by IL-4, rather than as a brake. The interleukin’s own signature was not blunted by the presence of the inflammatory signal; it was broadened by it. This finding suggests that the anti-inflammatory cytokine does not merely survive contact with its proinflammatory counterpart but actively exploits TNF signaling to shape the scope of its own transcriptional output.

The selectivity of the reverse direction is equally striking. IL-4 did not shut down TNF signaling wholesale. Instead, it targeted a specific component of the TNF-induced program: the interferon response. Genes driven by interferon regulatory pathways, which form an important antimicrobial and immune-activating arm of TNF signaling, were selectively inhibited by IL-4. The broader inflammatory gene expression elicited by TNF, however, remained largely intact. In other words, IL-4 pruned the interferon branch of the TNF response while leaving the rest of the inflammatory tree standing. This level of precision implies that the two cytokines negotiate at the level of individual gene programs rather than through a simple global on-off switch.

Among the genes that responded synergistically to the combined cytokines were sets with well-recognized roles in regulating inflammation and promoting tissue repair. When TNF and IL-4 were present together, these gene sets were induced to levels far exceeding what either cytokine achieved alone. The synergy was not a minor quantitative effect confined to a handful of transcripts; it encompassed coordinated gene programs that shape how macrophages behave in damaged tissue. Because macrophages are central orchestrators of the transition from inflammation to repair, the identity of the genes governed by this combined signal carries weight for understanding how wounds progress from the inflammatory phase to the rebuilding phase.

To test whether this laboratory-scale crosstalk mattered in a living tissue context, the investigators turned to a skin wound-healing model. Their analysis revealed that the synergistically induced gene sets were highly expressed during precisely the phase of wound repair when TNF and IL-4 are co-expressed in the healing tissue. This temporal overlap is biologically meaningful. It suggests that the cooperative program observed in cultured human monocytes is not an artifact of the dish but reflects a naturally occurring transcriptional state in which the two cytokines act together in time and space. During the window when inflammation and repair must be balanced, the combined TNF and IL-4 signal appears to help define the macrophage phenotype that supports that balance.

Mechanistically, the study traced the crosstalk to epigenetic chromatin-mediated mechanisms rather than to changes in signaling alone. Transcription factors are the proteins that bind DNA and switch genes on, but whether they can reach their targets depends on the state of the chromatin, the packaged form of DNA in the cell. The researchers found that cooperation between NF-κB, the canonical transcription factor activated by TNF, and STAT6, the transcription factor activated downstream of the IL-4 receptor, underpinned the synergistic gene expression. Rather than acting through separate gene sets, these two pathways converged on shared regulatory elements, allowing a proinflammatory signal and an anti-inflammatory signal to jointly open and activate the same loci.

A second epigenetic mechanism involved the erasure of a repressive histone mark. Histone H3 lysine 27 trimethylation, abbreviated H3K27me3, is a chemical modification of chromatin that is generally associated with silenced or po genes held in a inactive state. In the presence of the combined cytokine signal, this negative mark was removed from relevant genomic regions, lifting a layer of repression and permitting transcriptional activation. The removal of H3K27me3 provides a plausible explanation for how the synergy produces gene induction that neither cytokine can accomplish alone: TNF signaling through NF-κB helps remodel the chromatin landscape in a way that makes IL-4-driven, STAT6-dependent transcription possible at genes that would otherwise remain closed.

The third mechanistic pillar was the selective inhibition of IRF1, a transcription factor that mediates interferon responses and contributes to the interferon arm of TNF signaling. By suppressing IRF1, IL-4 was able to disassemble the interferon component of the TNF program without dismantling TNF-driven inflammatory gene expression more broadly. This selective targeting helps explain the otherwise paradoxical combination of results: cooperation at repair-related and inflammation-regulating genes on one hand, and selective antagonism at interferon-responsive genes on the other. The crosstalk is therefore not a single mechanism but a coordinated set of chromatin-level events that produce different outcomes at different classes of target genes.

The authors frame these results as identifying a mechanism for the expansion of the IL-4 response, and the implications extend beyond basic cytokine biology. If TNF signaling is required for the full breadth of the IL-4 program in monocytes and macrophages, then broadly suppressing TNF, as many anti-TNF therapies do in conditions such as rheumatoid arthritis and inflammatory bowel disease, may have consequences that reach into the tissue-repair arm of immunity, not only the inflammatory arm. The study also highlights the complexity of crosstalk between antagonistic cytokines more generally, showing that pairs of signals long assumed to cancel each other out can instead cooperate on select gene responses that are important for immune function and tissue repair. Cross-inhibition, the traditional focus of the field, turns out to be only part of the story.

As with any study, the findings come with scope conditions worth keeping in view. The human cell work was performed in primary monocytes and macrophages, and the in vivo evidence comes from a skin wound-healing model, so extending the conclusions to other tissues, other disease settings, and other cytokine combinations will require further investigation. Nevertheless, the work offers a concrete and testable framework: antagonistic cytokines negotiate through transcription factor cooperation, targeted histone modification, and selective inhibition of intermediary factors such as IRF1. For a field that has long organized itself around the idea that inflammatory and anti-inflammatory signals are opponents, the demonstration that TNF can serve as a costimulator of the IL-4 program, and that the two jointly govern genes central to repair, is a reminder that the immune system’s wiring is built less on simple opposition than on context-dependent partnership.

Subject of Research: Crosstalk between the cytokines TNF and IL-4 in regulating gene expression in human monocytes and macrophages

Article Title: IL-4 exploits TNF signaling to shape its gene expression signature in monocytes and macrophages

Article References: Yuan, R., Yang, C., Mishra, B., Oliver, D., Bell, R. D., & Ivashkiv, L. B. (2026). IL-4 exploits TNF signaling to shape its gene expression signature in monocytes and macrophages. Nature Communications. https://doi.org/10.1038/s41467-026-78528-3

Image Credits: AI Generated

DOI: 10.1038/s41467-026-78528-3

Keywords: IL-4, TNF, monocytes, macrophages, cytokine crosstalk, NF-kB, STAT6, H3K27me3, IRF1, gene expression, wound healing, immunology