A new study shows that at least 1 in 5 hospitalized COVID-19 patients develops antibodies that attack their own tissue within a week of admission.

Autoantibodies are antibodies directed at their own tissues or at substances immune cells secrete into the blood. Autoantibodies can be early harbingers of full-blown autoimmune disease.

“If you get sick enough from COVID-19 to end up in the hospital, you may not be out of the woods even after you recover,” says PJ Utz, professor of immunology and rheumatology at Stanford Medicine.

As reported in Nature Communications, researchers looked for autoantibodies in blood samples drawn during March and April of 2020 from 147 COVID-19 patients at three university-affiliated hospitals: Philipps University Marburg in Germany, the University of Pennsylvania, and Stanford, and from a cohort of 48 patients at Kaiser Permanente in California. They used blood samples drawn from other donors prior to the COVID-19 pandemic as controls.

The researchers identified and measured levels of antibodies targeting the virus; autoantibodies; and antibodies directed against cytokines, proteins that immune cells secrete to communicate with one another and coordinate their overall strategy.

Upward of 60% of all hospitalized COVID-19 patients, compared with about 15% of healthy controls, carried anti-cytokine antibodies, the researchers found. This could be the result of immune-system overdrive triggered by a virulent, lingering infection. In the fog of war, the abundance of cytokines may trip off the erroneous production of antibodies targeting them, Utz says.

If any of these antibodies block a cytokine’s ability to bind to its appropriate receptor, the intended recipient immune cell may not get activated. That, in turn, might buy the virus more time to replicate and lead to a much worse outcome.

For about 50 patients, blood samples drawn on different days, including the day they were first admitted, were available. This allowed the researchers to track the development of the autoantibodies.

Read the full article about self-attacking antibodies by Bruce Goldman at Futurity.