UCSF Study Identifies Lung Fibroblasts as Primary Drivers of Life-Threatening Inflammaging During Flu and COVID-19 Infections

UCSF researchers find that aging lung fibroblasts trigger a damaging immune cycle in COVID and flu. Learn how "inflammaging" leads to severe ARDS in 2026.

By: AXL Media

Published: Mar 28, 2026, 4:53 AM EDT

Source: Information for this report was sourced from University of California - San Francisco

The Role of Structural Cells in Age-Related Inflammation

In older adults, a minor respiratory infection can frequently escalate into a life-threatening hospital stay due to a phenomenon known as inflammaging. According to a new study led by Dr. Tien Peng at UCSF, the structural cells of the lung, known as fibroblasts, are not just passive scaffolding but active participants in this inflammatory spiral. While fibroblasts are primarily responsible for maintaining the airtight chambers of the lungs, they can also emit age-related distress signals that disrupt healthy tissue. This research shifts the focus from the immune system alone to the aging lung tissue itself as a primary driver of severe disease outcomes.

Activation of the NF-kB Pathological Circuit

The study highlights a specific signaling pathway called NF-kB, which is frequently associated with the diseases of aging. When researchers engineered young mice to activate this pathway within their lung fibroblasts, the animals' lungs began to mimic the environment of an elderly person. This signal prompted the lung's resident macrophages to rally an unnecessary immune response, creating clusters of inflamed cells. According to the findings published in Immunity, this circuit of dysfunction suggests that the lung tissue essentially "primes" itself for an overreaction before a virus even enters the system.

The Emergence of Pro-Inflammatory GZMK Cells

A critical component of this inflammatory cluster is a specific type of immune cell marked by the GZMK gene. These cells, which were first observed in high concentrations in severe COVID-19 patients, rush into the lungs from the bloodstream in response to fibroblast signals. Although these GZMK cells proved to be impotent against actual viral pathogens, they remained highly capable of damaging healthy lung tissue. The UCSF team found that the presence of these cells alone was enough to make young lungs experience the severe symptoms typically reserved for the elderly, regardless of the actual viral load.