It is part of the innate immune system and normally helps to fight infections and eliminate damaged and infected body cells. "In patients with long COVID, the complement system no longer returns ...

Although the very idea of 'innate' immune responses preceded the discovery of TLRs and non-TLR innate proteins (natural antibodies and complement ... the innate immune system as a potential ...

indicating inflammation of myeloid cells and activation of a family of immune system proteins called the complement system.