Lung fibrosis has long been viewed as a one-way street: once scar tissue forms in the lungs, it remains. Medicines could slow progression, but none could reverse existing scarring. A study published in May 2026 in Science Translational Medicine by Heidelberg University Hospital now shows for the first time that this mechanism can be broken. The key lies with natural killer cells, which normally eliminate defective tissue cells but are blocked in fibrotic lungs by a molecular brake.
What Lung Fibrosis Does and Who It Affects
Lung fibrosis refers to permanent scarring of lung tissue, which destroys its elasticity and oxygen exchange capacity. In inflammatory rheumatic diseases such as systemic sclerosis (scleroderma) or rheumatoid arthritis, interstitial lung disease with fibrotic changes is one of the most common causes of death. Systemic sclerosis, for instance, leads to lung involvement in roughly 70 percent of patients, with a five-year survival rate of less than 50 percent in severe fibrosis cases.
Current therapies such as the antifibrotics nintedanib and pirfenidone slow progression but do not reverse it. Clinical trials of CAR-T cell therapies for scleroderma in 2023 and 2024 showed initial promising results but remain in early phases. The Heidelberg team is pursuing a different mechanistic approach.
The Immune Brake and How to Release It
According to a press release from Heidelberg University Hospital from May 13, 2026, the research team led by rheumatologist Dr. Wolfgang Merkt and his co-author Dr. David Lagares, formerly at Massachusetts General Hospital and Harvard Medical School, identified a specific mechanism: senescent fibroblasts (aged cells in scar tissue) express abnormally high levels of the molecule HLA-E. This binds to the inhibitory receptor NKG2A on natural killer cells, preventing them from recognising and eliminating the fibroblasts.
Monalizumab, an antibody originally developed in cancer medicine and already in clinical testing, blocks this exact NKG2A receptor. In preclinical models and human ex vivo studies, researchers observed that when NK cells are freed from this blockade by monalizumab, they can selectively eliminate senescent fibroblasts. According to a press release from the German Society for Rheumatology (DGRh), Prof. Dr. Ulf Wagner, DGRh president, called the study "potentially revolutionary for fibrotic lung diseases in rheumatic patients."
What the Finding Means and What It Does Not
The finding is a proof of concept, not a therapeutic breakthrough. The study uses laboratory models and ex vivo tissue, meaning cells outside the living body. A clinical trial in humans for this specific approach in lung fibrosis has not yet begun. While monalizumab is an approved drug for other indications, which could accelerate entry into clinical trials, this does not automatically mean it will produce the same effect in the lungs.
The CAR-T approach in scleroderma illustrates how long this pathway can take: first publications on T cell therapies for autoimmune diseases appeared around 2021, and initial Phase I trials started in 2023. Between laboratory proof and approved therapy, seven to fifteen years and multiple phases of clinical testing typically elapse, during which safety, dosage, and efficacy in patients are tested.
Broader Potential: Idiopathic Fibrosis
Beyond rheumatic fibrosis, the approach could be relevant for a second disease group: idiopathic pulmonary fibrosis (IPF). IPF is a severe lung disease of unknown cause, considerably more common than rheumatic lung involvement. Median survival time after diagnosis without transplantation is two to four years. Senescent fibroblasts also play a central role in IPF. In their study, the Heidelberg researchers note that the approach could potentially transfer to other fibrosis pathologies if the HLA-E/NKG2A mechanism is similarly active there, which requires further investigation.
For the German Center for Lung Research (DZL), under whose funding the study was conducted, the finding demonstrates that translational research—the direct bridge from basic science to clinically relevant approaches—delivers results. The DZL funds collaborative research among several German university hospitals with the goal of curing lung diseases rather than merely slowing them.
When Clinical Trials Could Begin
According to Heidelberg University Hospital, Dr. Wolfgang Merkt stated that the next steps include preparing a Phase I trial in patients with rheumatic lung fibrosis. Monalizumab's known safety profile from cancer medicine is an advantage here: regulators typically require less preclinical data for an already-tested drug than for an entirely new substance. The research team does not specify realistic timeframes for first human clinical results, which is standard in research: premature promises undermine trust if later phases fail.
What remains is the conceptual step. That lung scars are not necessarily permanent was not clear from previous scientific understanding. That the body's own immune system could accomplish scar breakdown if the right brake is released is a finding that could lay the foundation for an entirely new class of therapies, even if the path ahead remains long.