TLR7: What is it, why in COVID-19? Answers in Wikipedia.

A report of severe COVID-19 cases in four young men with mutations in their TLR7 genes came out a few days ago.

That is significant because TLR7 is part of the innate immune system. It recognizes the single-stranded RNA that SARS-COV-2 uses. When the virus injects itself into a cell, it is this RNA which hijacks the cell’s processes to reproduce itself.

TLR7 starts an immune cascade that results in the production of large amounts of type 1 interferons and other responses that have not yet been fully characterized (TLR proteins were only discovered recently and TLR7 specifically in 2004.)

You can find all the details in the Wikipedia articles about “toll-like receptors” and “TLR7”. There are also some scientific articles of interest, like this one: “Toll-like receptor signalling pathways” from 2014 in the journal “Frontiers in Medicine.”

The Wikipedia article on TLR7 mentions the study on the four young men with severe COVID-19, so they are up to date as well.