In the severe form of Covid-19, as in systemic lupus erythematosus, the immune cells do not have time to specialize, which considerably weakens their effectiveness against the disease.
- Severe forms of Covid-19 cause our immune system to work like when faced with lupus.
- B cells are produced in large numbers by our body, but are not specialized enough to fight disease effectively.
- Researchers are now trying to find out if the coronavirus would not force our body to have autoimmune reactions, which would explain the sequelae still felt by cured Covid-19 patients.
If our body has so much trouble fighting Covid-19, it’s because the virus manages not to play on equal terms with our immune system. Researchers at Emory University (USA) have discovered that the immune reaction of our cells during a severe form of Covid-19 is similar to that produced by systemic lupus erythematosus, an autoimmune disease which attacks multiple organs. Our lymphocytes reproduce in number but do not specialize to fight infection, which explains why some people with SARS-CoV-2 produce a lot of antibodies against the virus without this being effective. The results of the study were published online on October 7, 2020 in the journal Nature Immunology.
A less marked specialization of B lymphocytes
To better understand, the scientists turned to the literature already available on Covid-19. In particular, they looked at cases where the coronavirus disrupts the germinal centers of the lymph nodes, the place where our white blood cells reproduce and specialize. In the severe forms of Covid-19, the B lymphocytes, responsible for creating antibodies, leave the germinal centers by an extrafollicular route without having differentiated, which makes them almost ineffective. This disordered reaction of B lymphocytes during severe forms of the coronavirus is the same as that produced by systemic lupus erythematosus.
In people with systemic lupus erythematosus, cells activate abnormally and become auto-antibodies that attack our own body, one of the characteristics of autoimmune diseases. In the case of systemic lupus erythematosus, these repeated attacks cause fatigue, joint pain, rashes and kidney problems.
Numerous but inefficient immune cells
To confirm their predictions, the researchers compared 10 critical cases of people with a severe form of Covid-19 admitted to intensive care with seven patients treated on an outpatient basis for a mild form of Covid-19. A control group of 17 people served as a comparison.
Patients with severe forms of Covid-19 had higher than average antibody levels at the very start of their infection. However, with B cells exiting via an extrafollicular route, they performed less well than those that specialized in the germinal centers. However, despite the high concentration of B lymphocytes in their body, four of the ten patients affected by a severe form of Covid-19 died of the disease.
“It wasn’t until the third or fourth patient in the intensive care unit whose cells we analyzed that we realized we were seeing patterns strongly reminiscent of acute flare-ups of systemic lupus erythematosus.”says Ignacio Sanz, chief of the rheumatology division in the department of medicine at Emory University and author of the study.
Ignacio Sanz and his team are now trying to determine if Covid-19 has other points in common with systemic lupus erythematosus, particularly in terms of autoantibodies, in order to help people who have been able to recover from Covid-19 but which have scars. “Other researchers have observed autoantibodies in the acute phase of the disease, and it will be important to understand whether long-term autoimmune responses may be linked to fatigue, joint pain and other symptoms experienced. by some survivors.”
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