The researchers found circulating antiphospholipid antibodies, which can be more common among people with autoimmune disorders, such as lupus.
However, these “autoantibodies”, which target a person’s own organs and systems, can also be activated in response to viral infections and activate other immune responses.
The team studied blood samples from 244 patients hospitalized for Covid-19.
They compared the blood samples to those from healthy controls and found the Covid-19 samples contained higher levels of the antibody IgG, which works with other immune cells, such as IgM, to respond to immune threats. Higher levels of IgG were also associated with Covid-19 disease Severity, such as in patients who required breathing assistance.
The researchers observed similar patterns, but to a lesser extent, after analyzing blood samples from 100 patients hospitalized for sepsis, which can leave the body in inflammatory shock following a bacterial or viral infection.
IgG helps bridge a gap between innate and adaptive immune responses – a process that helps the body recognize, respond to, and remember danger.
In normal cases, these features help protect the body from illness and infection.
However, in some cases, this response can become hyperextended or altered and exacerbate illness.
Further, when researchers removed IgG from the Covid-19 blood samples, they saw molecular indicators of “blood vessel stickiness” fall.
When they added these same IgG antibodies to the control samples, they saw a blood vessel inflammatory response that can lead to clotting.
Since every organ has blood vessels in it, circulating factors that lead to the “stickiness” of healthy blood vessels during Covid-19 may help explain why the virus can affect many organs, including the heart, lungs, and brain. The researchers noted future studies could explore the potential benefits of screening patients with Covid-19 or other forms of critical illness for antiphospholipids and other autoantibodies and at earlier points of infection.
This may help identify patients at risk for extreme blood clotting, vascular inflammation, and respiratory failure.
When they added the same IgG antibodies to control samples, they noticed an inflammation of blood vessels which can cause clotting.
Since all organs have blood vessels in it, the circulating factors that contribute to the “stickiness” of healthy blood vessels during Covid-19 could help explain how the virus can affect a variety of organs, such as the lungs, heart, and brain. The researchers also noted that future studies could investigate the potential advantages of checking patients with Covid-19 or other types of critical disease for antiphospholipids and other autoantibodies, and at earlier stages of infection.
This could help identify those at risk of extreme blood clotting, vascular inflammation as well as respiratory failure.