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Mount Sinai study finds autoimmunity drives long COVID symptoms in some patients

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New Study Links Long COVID to Autoimmunity, Opening Door for Targeted Treatments

"The findings may allow clinicians to identify which long COVID patients have autoantibodies and could benefit from existing autoimmune therapies."

A groundbreaking study published in Cell on May 28 provides strong evidence that autoimmunity—where the immune system mistakenly attacks the body's own tissues—is a key driver of long COVID symptoms in a subset of patients.

The Research: Transferring Symptoms to Mice

Led by researchers at Mount Sinai, the study took a direct approach to proving the link. Scientists collected and purified antibodies from the blood of 87 long COVID participants and then infused these antibodies into healthy mice. The result was striking: the mice developed symptoms mirroring those of human long COVID patients.

Clinical Implications: Identifying Who Can Be Treated

This breakthrough offers immediate practical value for clinicians. Previously, treating long COVID with autoimmune therapies like intravenous immunoglobulin (IVIG) or FcRn inhibitors has produced inconsistent results.

Now, the study provides a clear biomarker—circulating autoantibodies in the blood—that can predict which patients will respond to these treatments. Other potential therapies under investigation include CAR-T cell therapy and plasmapheresis.

A Public Health Warning on Blood Donation

Co-senior author David Putrino raised an important safety concern. He noted that in the United Kingdom, long COVID is an exclusion criterion for blood donation, while in the United States it is not.

"U.S. donation policies should be reconsidered due to potential risks from plasma of individuals with long COVID."
— Co-senior author David Putrino

The Scope of the Problem

Long COVID remains a widespread and poorly understood condition. Studies estimate that 4-20% of all COVID-19 patients experience persistent symptoms, which can include:

  • Profound fatigue
  • Cognitive impairment ("brain fog")
  • Heart palpitations
  • Chronic pain

Proposed mechanisms for the condition have included viral persistence, reactivation of latent viruses, and immune dysregulation. This new study adds conclusive evidence for autoimmunity as a major factor in a significant subset of patients.