We pursued a study of immune responses in COVID-19 and influenza cohorts. Compared to influenza patients, COVID-19 patients exhibited largely equivalent lymphocyte counts, fewer monocytes, and lower surface HLA-class II expression on select monocyte populations. Furthermore, decreased HLA-DR on intermediate monocytes was a significant predictor of COVID-19 disease severity.
In contrast to prevailing assumptions about COVID-19 disease immunopathology, very few (7 of 168) COVID-19 patients exhibited cytokine profiles indicative of Cytokine Storm Syndrome. After controlling for key confounding factors such as age and sample time point, COVID-19 patients exhibited lower cytokine levels than influenza patients. Up-regulation of IL-6, GCSF, IL-1RA, and MCP1 predicted death from acute respiratory failure among COVID-19 patients but were not statistically higher than influenza patients.
Single-cell transcriptional profiling was concordant with profound suppression in interferon signaling among COVID-19 patients. When considered across the spectrum of peripheral immune profiles, COVID-19 patients are less inflamed than influenza patients.