Immune System: The complement system is a part of the immune system that helps eliminate pathogens, but if it is activated in excess, it can be harmful.
Understanding how our immune system responds to infection with the Covid-19 virus is one of the keys to focus on treating the disease.
1. Complement System
Our immune system is very complex. One of its parts is the so-called complement system, which is part of innate immunity and is one of our oldest defense systems.
The complement system is a defense mechanism whose mission is to eliminate pathogens from the circulation. However, when activated in excess, it can be harmful.
2. Complement System and Covid-19
A recent study by researchers from the Irving Medical Center of Columbia University (United States), published in Nature Medicine, indicates that the complement system could influence the severity of Covid-19.
As previous studies indicate, coronaviruses can mimic proteins involved in coagulation and proteins that make up the complement system.
Coronaviruses mimic proteins of the complement system.
Complement proteins work a bit like antibodies and help kill pathogens by attaching themselves to viruses and bacteria. The complement system can also increase clotting and inflammation in the body.
“The new coronavirus, by mimicking the complement or coagulation proteins, could lead both systems to a hyperactive state.”
3. Macular Degeneration and Increased Severity of Covid-19
The researchers wanted to see if people who previously had clotting or complement system disorders were more susceptible to the Covid-19 virus.
To do this, they looked at people with Covid-19 with age-related macular degeneration (an eye disease caused by an excessive response of the complement system), as well as common bleeding disorders such as thrombosis and bleeding.
They found that people with age-related macular degeneration are at increased risk of complications or death from Covid-19.
4. Coagulation in People With Covid-19
The researchers found that people with a history of bleeding disorders also had a higher risk of dying from Covid-19 virus infection.
“The complement system is also more active in obesity and diabetes and may help explain, at least in part, why people with these conditions are also at increased risk of mortality from COVID.”
5. Activation of the Complement System
The study also revealed that in people with Covid-19, the virus induces a strong activation of the body’s complement and clotting systems.
“We found that the complement system is one of the most differential expression pathways in patients infected with SARS-CoV-2,” the authors indicate.
“As part of the immune system, you would expect to see the complement system activated, but it seems that it is beyond what you would see in other infections such as the flu.”
The COVID-19 virus induces strong activation of complement and coagulation systems.
“These results provide important information on the pathophysiology of Covid-19 and show the role of complement and clotting pathways in determining the clinical outcomes of patients infected with SARS-CoV-2.”
The studies authors suggest that drugs that inhibit the complement system could help treat severe Covid-19 patients.