Figure 2.

COVID-19 patient serum induces C5b-9 and C3c deposition on the cell surface. COVID-19 patient serum led to increased cell surface C5b-9 deposition in all complement pathway buffer (A) and alternative pathway specific buffer (B). C3c deposition was increased compared to control normal human serum (NHS) in all complement pathway buffer (C) and alternative pathway specific buffer (D). Statistical significance was calculated between each disease group and the NHS control group. EDTA: ethylenediaminetetraacetic (used as a negative control); Sia: sialidase (used as a positive control for alternative pathway of complement [APC] activation); stx1: Shiga toxin subunit 1 (used as a positive control for all complement pathways activation). Vent: ventilation.