Researchers at Uppsala University carried out a study to understand the overreaction of the innate immune system in patients with severe Covid-19.

The authors wrote that this overreaction may underlie the formation of blood clots (thrombi) and deterioration in oxygen saturation that affect patients.

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The study, published in the journal Frontiers in Immunology, stated that blood contains numerous proteins that constitute the body’s primary barrier for the entry of various pathogens, including SARS-CoV-2. These proteins are part of the intravascular innate immune system (IIIS).

Only 5 per cent of present-day animal species have an immune system that includes T cells and B cells. The rest rely solely on the natural immune system. With its innate ability to eliminate pathogens, such as microorganisms and damaged cells, the IIIS serves as a kind of waste disposal system.

For the current study, the researchers examined 66 hospital inpatients with severe Covid-19 who were receiving care in the intensive care unit and found pronounced activation of the IIIS.

“It’s probably the tissue damage, with dead cells in the lungs, that initiates this activation. It can potentially lead to clot formation and poor oxygen saturation due to increased leakage into the blood vessels,” says lead author Bo Nilsson, Professor at the Department of Immunology, Genetics, and Pathology.

Also read: B cell responses to Covid-19 stable after 5 months but do not recognize new strains

The degree of activation is, in prognostic terms, connected with survival and lung function.

The researchers explained that in some patients with Covid-19, the cell damage is so extensive that the IIIS overreacts, and rather than helping clean out the tissue, makes matters worse.

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