The immune system is a complex orchestra with many cell types, each having its own part to play. When an injury occurs, the very first cells to arrive at the site are neutrophils. Historically, researchers thought of these cells as a simple clean-up crew that just clears away debris from the injury site. However, the Becker team discovered that a specific subgroup of these neutrophils has a crucial job: like a conductor in an orchestra, these cells signal the rest of the immune system to dial down their response back into a harmonious rhythm of regeneration. Their secret? A signaling molecule called Il-4.
The Becker group worked with larval zebrafish to understand the role of neutrophils and the Il-4 signaling molecule at the injury site. When this specific cell group was inactivated in the experiment, the situation spiraled completely out of balance. Other immune cells began overproducing highly inflammatory proteins, leading to an uncontrolled overreaction. This effectively stalled the fish's ability to regrow nerve fibers and recover their movement. However, when the researchers artificially added the Il-4 signaling molecule to the injury sites, the inflammation calmed down and the spinal cords regenerated perfectly – even without the physical presence of neutrophils.
"For the first time, we have shown that neutrophils play a massive, active role in successfully repairing a spinal cord," says Prof. Thomas Becker, who led the study. "They aren't just there to clear away debris; they act like conductors that tell other immune cells to return to a harmonious rhythm. Without them, the immune system locks into a destructive cycle and prevents healing. By using the Il-4 molecule, the neutrophils smooth out the inflammation, allowing the delicate nerve fibers to grow right through the injury zone."
The stark contrast between how zebrafish and humans respond to spinal cord injuries is a major puzzle in regenerative medicine. While a human's immune response to injury often causes permanent damage to the central nervous system, the zebrafish provides a roadmap for unrealized medical potential. The study not only cements the finding that the fine regulation of inflammation is crucial for healing but also shows exactly how unleashing the right signals at the right time can reactivate nerve regeneration.
“Of course, the question is to what extent our results apply to humans. It remains to be seen if Il-4 plays a similar role in humans and whether it can finely balance the inflammation, allowing for better healing at the injury site,” says Xiaobo Tian, who conducted the study. “It is definitely a very promising avenue for future studies in humans.”
The study was led by Xiaobo Tian and an international team of scientists at the Center for Regenerative Therapies Dresden (CRTD) at TU Dresden, the Cluster of Excellence Physics of Life , and the Centre for Discovery Brain Sciences at the University of Edinburgh. It was funded by the Chinese Scholarship Council and the Alexander-von-Humboldt Foundation.
Xiaobo Tian, Alberto Docampo-Seara, Kim Heilemann, Friederike Kessel, Daniela Zöller, Anja Bretschneider, Thomas Becker & Catherina G. Becker: A reparative neutrophil subpopulation accelerates spinal cord regeneration in zebrafish by controlling macrophage inflammation via Il-4. Journal of Neuroinflammation (June 2026).
Link to the study: https://doi.org/10.1186/s12974-026-03878-0
Animal research still plays an essential role in scientific research. Animal research is also carried out in medicine and life sciences at TUD only if they are indispensable for specific scientific questions and for the welfare of humans. Scientists who conduct research on animals are invariably caught between the conflicting ethical priorities of animal welfare and important scientific findings that could, for example, form the basis for the development of new life-saving drugs and therapies. All animal research is subject to legal regulations and high ethical standards such as the 3R principles. Further information on this topic is available on the following website: https://tud.link/tfbwcc
The Center for Regenerative Therapies Dresden (CRTD) of TUD Dresden University of Technology is an academic home for scientists from around 25 nations. Their mission is to discover the principles of cell and tissue regeneration and leverage this for the recognition, treatment, and reversal of diseases. The CRTD links the bench to the clinic, scientists to clinicians to pool expertise in stem cells, developmental biology, gene-editing, and regeneration towards innovative therapies for neurodegenerative diseases such as Alzheimer's and Parkinson's disease, hematological diseases such as leukemia, metabolic diseases such as diabetes, bone and retina diseases.
The CRTD was founded in 2006 as a research center of the German Research Foundation (DFG) and funded until 2018 as a DFG Research Center, as well as a Cluster of Excellence. Since 2019, the CRTD is funded by the TU Dresden and the Free State of Saxony. The CRTD is one of three institutes of the central scientific unit Center for Molecular and Cellular Bioengineering (CMCB) of the TU Dresden.
Dr. Magdalena Gonciarz
PR Officer
Center for Molecular and Cellular Bioengineering
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E-Mail: cmcb_press@tu-dresden.de
Journal of Neuroinflammation
A reparative neutrophil subpopulation accelerates spinal cord regeneration in zebrafish by controlling macrophage inflammation via Il-4
26-May-2026