Long COVID Immune Dysfunction Linked to NK Cells

A study published in Frontiers in Immunology found that long COVID is associated with significant dysfunction of Natural Killer (NK) cells, key components of the innate immune system that identify and eliminate infected or abnormal cells.

Researchers observed that individuals with long COVID had both reduced NK cell numbers and signs of functional exhaustion, suggesting these cells may be less effective at carrying out their normal immune roles. Despite this, patients showed elevated antibody levels alongside reduced cytokine signaling, indicating a mismatch in immune activity rather than a fully resolved response.

The study also identified gene expression changes linked to neurological symptoms, including pathways associated with smell, taste, and cognitive function. These findings suggest that immune dysfunction may contribute not only to systemic symptoms like fatigue but also to the neurological effects commonly reported in long COVID.

Overall, the findings support a state of persistent immune dysregulation, in which the immune system remains altered long after the initial infection has resolved.

Citation

Ray U, Schulze Selting A, Perera RP, Yang Z, Lysenkov V, Göpel S, Bitzer M, Salker MS, Ossowski S, Riess O, Casadei N and Singh Y (2026) Dysregulated NK-cell gene expression defines the enduring symptoms of long COVID-19. Front. Immunol. 17:1720551. doi: 10.3389/fimmu.2026.1720551