Scientists at the Massachusetts Institute of Technology in the USA have revealed why COVID-19 manifests itself differently in different patients and leads to severe complications, including multisystem inflammatory syndrome (MIS-C) in children. The reason has to do with certain types of antibodies that cause unwanted reactions. The researchers’ article was published in the journal Nature Medicine.
Experts have shown that children with MIS-C, which developed after COVID-19, have high levels of IgG antibodies. IgG usually helps control infection, but in the case of MIS-C, these antibodies activate immune cells. IgGs interact with macrophages, causing them to be overactive. Since macrophages are present in many tissues and organs, inflammatory processes that cover them develop.
Adults with severe COVID-19 have elevated levels of IgA antibodies that interact with a type of immune cell called neutrophils and cause them to secrete cytokines. If there are too many IgA antibodies, it can cause a cytokine storm.
The researchers hope the discovery will help develop therapies that prevent or alter the immune response while maintaining its protective functions, but reducing harmful responses.