A group from Medical University of Innsbruck, Innsbruck, Austria, etc. has reported on T cell immunity and related humoral immune responses of COVID-19.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8237940/
It was clearly demonstrated that SARS-CoV-2 specific CD8+ T lymphocytes and higher IFNγ production was significantly induced in patients with mild compared to patients with severe or critical COVID-19. In all patients, SARS-CoV-2-specific antibodies with similar neutralizing activity were detected, In other words, no significant differences in viral neutralization could be observed between patients with mild, severe or critical COVID-19. And further, elevated anaphylatoxin C3a and C5a levels were identified in severe and critical COVID-19 patients probably caused by aberrant immune complex formation due to elevated antibody titers in these patients. Normally, complements should be protective during viral infections, but with respect to COVID-19, local complement activation might be related to tissue damages leading to severe.
This study indicates that early and polyfunctional CD8+ T cell immunity along with low anaphylatoxin expression is associated with mild.
In addition, authors proposed an idea of blocking the C5a–C5aR1 axis as therapeutic strategy to limit excessive lung inflammation and tissue damage caused by infiltrating myeloid cells.
