"SARS-CoV-2 infects human CD4+ T helper cells, but not CD8+ T cells... in blood and bronchoalveolar lavage T helper cells of severe COVID-19 patients"
"spike glycoprotein (S) directly binds to the CD4 molecule, which... also requires ACE2 and TMPRSS2"
Impairs adaptive immunity.
Note TMPRSS13 expression as well.
SARS-CoV-2 can use TMPRSS13 to cleave Spike and deploy FP with approximately equal efficiency to TMPRSS2.
It can also use certain TMPRSS11 subtypes, albeit more slowly.
Severe COVID-19, much like SARS, heavily damages the spleen and lymph nodes.
Meanwhile:
Results on SARS-CoV-2 infection of the lymphatic system and lymphocytes have been widely replicated (no pun intended):
However, the differentially greater susceptibility of CD4+ T cells has major implications for the nature of the inflammatory state.
Immunomodulatory treatments like thymosin α1 might help improve the CD4/CD8 ratio:
oatext.com/pdf/MRI-3-157.…
Conversely, CD4/CD8 ratios also fall in e.g. HIV/AIDS:
urmc.rochester.edu/encyclopedia/c…
And SARS:
academic.oup.com/cid/article/37…
Note elevated 5-HT levels also promote inflammatory hypersensitivity reactions from T lymphocytes.
jni-journal.com/article/S0165-…
5-HT specifically suppresses activation of CD4+ lymphocytes, further exacerbating the effects of their selective viral depletion.
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