Abnormal Immune Antibodies Targeting the Nervous System Linked to Brain Fog and Chronic Fatigue in Long COVID
Nikhil Prasad Fact checked by:Thailand Medical News Team May 06, 2026 1 hour, 9 minutes ago
Medical News: A new scientific study is shedding fresh light on why many people with Long COVID and Chronic Fatigue Syndrome continue to struggle with exhaustion, dizziness, memory issues, and “brain fog” long after their initial illness has passed. Researchers in Spain have discovered that abnormal immune antibodies may be interfering with the nervous system and even affecting cognitive performance.
New research suggests immune antibodies may disrupt the nervous system and contribute to Long COVID fatigue,
dizziness, and brain fog
The research was conducted by scientists from the Biobizkaia Health Research Institute, Cruces University Hospital, Donostia University Hospital, University of the Basque Country UPV/EHU, University of Deusto, Biogipuzkoa Health Research Institute, CIBERNED-Institute Carlos III in Madrid, and The Basque Foundation for Science IKERBASQUE in Spain.
Scientists Investigate Hidden Immune Triggers
The study focused on patients suffering from Post-COVID Condition, commonly known as Long COVID, and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Both illnesses are known for causing severe fatigue, rapid heartbeat, dizziness, concentration problems, muscle pain, and poor exercise tolerance.
Researchers analyzed blood samples from 96 Long COVID patients, 59 ME/CFS patients, and 36 healthy volunteers. They specifically looked for autoantibodies, which are antibodies that mistakenly attack the body’s own tissues instead of protecting it from infection.
The scientists examined antibodies targeting G protein-coupled receptors, important signaling receptors involved in heart rate, blood pressure, nervous system balance, memory, and brain communication.
Abnormal Antibodies Found in Many Patients
One of the most striking findings was that ME/CFS patients had significantly higher levels of beta-2 adrenergic receptor antibodies compared to healthy individuals and Long COVID patients.
Meanwhile, Long COVID patients showed a higher percentage of abnormal antibodies targeting M3 muscarinic receptors. These receptors are important for nerve signaling and automatic body functions such as digestion, sweating, circulation, and heart rhythm.
The researchers believe these antibodies may disrupt the autonomic nervous system, the system responsible for controlling involuntary body functions like breathing, blood pressure, and heartbeat.
Many patients in both illness groups showed signs of dysautonomia, a condition where the autonomic nervous system stops functioning properly. Over 35 percent of ME/CFS patients met the criteria for POTS, or Postural Orthostatic Tachycardia Syndrome, compared to nearly 15 percent of Long COVID patients.
Brain Fog and Memory Problems May Be Immune Driven
One of the more surprising discoveries involved cognitive performance. The researchers found that certain muscarinic receptor antibodies were linked to memory and working memory performance in ME/CFS patients. Higher levels of some antibodies correl
ated with better verbal and working memory scores, although the scientists warned that this does not necessarily mean the antibodies are beneficial.
Instead, the antibodies may be acting in a complicated compensatory way inside the brain, possibly altering nerve signaling in response to existing neurological dysfunction.
This
Medical News report highlights how these findings further strengthen growing evidence that Long COVID and ME/CFS are not simply psychological conditions, but complex biological illnesses involving immune and nervous system abnormalities.
The researchers explained that muscarinic receptors are heavily involved in learning, memory formation, and communication between brain cells, especially in regions like the hippocampus and prefrontal cortex.
Evidence Of Nervous System Dysfunction
The study also included extensive autonomic nervous system testing. Patients underwent tilt-table testing, deep breathing tests, heart rate variability measurements, and sudomotor testing that evaluated sweating and nerve responses.
Long COVID patients with higher beta-2 receptor antibody levels showed stronger autonomic symptoms including abnormal heart rate responses and signs of sympathetic nervous system overactivation.
Researchers also found evidence suggesting that these antibodies may contribute to imbalances between the sympathetic and parasympathetic nervous systems, which normally work together to keep the body stable.
Researchers Urge More Investigation
Although the findings are important, the scientists emphasized that the study was exploratory and does not yet prove that the antibodies directly cause symptoms. The blood tests used could only detect whether antibodies were present and could not determine exactly how they behave inside the body.
Still, the research adds to mounting international evidence suggesting that autoimmune reactions may play a major role in Long COVID and ME/CFS.
The researchers concluded that these illnesses appear to involve deep interactions between the immune system and nervous system. They said the findings may eventually help doctors develop better diagnostic biomarkers and targeted treatments aimed at calming harmful immune responses and restoring nervous system balance. They also stressed that future studies involving larger patient groups and longer follow-up periods will be necessary to fully understand how these antibodies contribute to fatigue, autonomic dysfunction, and cognitive impairment.
The study findings were published in the peer reviewed journal: Scientific Reports.
https://www.nature.com/articles/s41598-026-49131-9
For the latest on Long COVID, keep on logging to Thailand
Medical News.
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