When the First Line of Defense Fails
Sepsis is one of the most critical medical emergencies. Even after surviving the acute phase of this condition, many patients remain at a heightened risk of developing further infections. A recent study from the Clinic for Trauma, Hand, and Reconstructive Surgery at the Medical Faculty of the University of Duisburg-Essen and Universitätsmedizin Essen has shed light on a significant mechanism that might explain this immune weakness.
The focus of this study is on natural killer (NK) cells, specialized immune cells that play a crucial role in combating pathogens. Following a sepsis event, these cells showed significantly diminished functionality for weeks. This decline in function was especially pronounced in patients who subsequently developed nosocomial (hospital-acquired) infections.
NK Cells Lose Their Ability for Effective Immune Defense
The research team, led by Prof. Stefanie Flohé, collected blood samples from patients in the Clinic for Anesthesiology and Intensive Care Medicine and the Clinic for Trauma, Hand, and Reconstructive Surgery. They discovered that the root cause of reduced NK cell function stems from disrupted metabolic adaptation. “For an effective immune response, NK cells require substantial amounts of energy and nutrients,” explains André van der Wurff, a doctoral candidate at the ELAN Graduate School. However, a crucial metabolic checkpoint— the mTORC1 protein— is not sufficiently activated during sepsis. Consequently, NK cells produce markedly less interferon-gamma, which is vital for fighting bacterial infections.
The Root Cause Lies in the Immune Cell Metabolism
“Our results indicate that the regulation of NK cell metabolism is persistently disturbed in sepsis, rendering them incapable of meeting the demands of an effective immune response,” elaborates Prof. Dr. Stefanie Flohé, the head of the Immunology/Sepsis Trauma group. The metabolic issues faced by these immune cells not only compromise their effectiveness but also leave patients vulnerable to opportunistic infections, which can worsen clinical outcomes.
New Perspectives for Future Therapies
The research team also explored whether it’s possible to restore the impaired function of NK cells. By inhibiting a broader metabolic regulator (AMPK), they successfully reactivated mTORC1, subsequently enhancing NK cell defense functions.
While these findings are still preliminary and do not yet represent a new therapy, they open up promising avenues for future treatment strategies. One potential objective could be to specifically restore the metabolic activity of NK cells, thereby reducing the risk of dangerous subsequent infections following sepsis.
Link to the Original Publication:
Disturbed metabolic adaptation drives natural killer cell dysfunction in association with nosocomial infection during human sepsis
