Researchers have identified an unexpectedly persistent population of monocyte-derived immune cells in mouse lungs that helps sustain local memory T cells after influenza infection. The study, published on August 31 in Nature Immunology, found that these cells produce galectin-1, a protein that strengthened lung immune memory when tested as an additive to an experimental nasal flu vaccine in mice. The finding suggests a possible route toward vaccines that build stronger defenses where respiratory viruses first enter, but it has not yet been demonstrated in people.
The University of Rochester Medical Center team focused on tissue-resident memory T cells, which remain in organs after infection and can respond rapidly to a returning pathogen. Such cells in the airways are an important target for next-generation influenza vaccines because they act at the initial site of infection. Conventional injected flu vaccines are effective at reducing disease but do not consistently establish strong tissue-resident memory in the respiratory tract, according to the university's account of the research.
Monocytes are generally regarded as short-lived members of the innate immune system. By tracking immune cells after influenza infection, however, the researchers found a distinct monocyte-derived subset that persisted in mouse lungs for months. The cells supported the survival and function of resident memory T cells, indicating that durable immune memory does not depend only on adaptive T and B cells. The paper describes the population as having high expression of galectin-1.
The experiments indicated that galectin-1 helps activate and maintain the lung memory T cells. Researchers added the protein to an experimental intranasal influenza vaccine and observed a significantly stronger immune response in the lungs of mice. The result identifies a biological mechanism and a potential vaccine-adjuvant candidate rather than a finished product. The study did not establish that the approach prevents influenza in humans, determine a human dose or resolve the safety questions required before clinical use.
The work matters because influenza continues to cause substantial illness and death, while vaccines delivered into muscle do not always prevent the virus from first taking hold in the nose and lungs. A vaccine that reliably enhances mucosal immunity could, in principle, attack infection earlier and complement antibody-based protection. The researchers said the same strategy might eventually be relevant to other respiratory viruses, although that broader possibility also remains untested.
The team is now working on more stable forms of galectin-1 that might be suitable as vaccine additives. Further studies must confirm the mechanism, assess toxicity and durability, and determine whether the mouse findings translate to human immune systems before trials can establish clinical value. For now, the research expands the scientific picture of immune memory by showing that a long-lasting innate-cell population can help maintain localized T-cell protection in the lung.
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