FIG 1.

Hospitalized COVID-19 is associated with differential antibody Fc-mediated innate immune functions. (a and b) The ability of anti-S1 (a) and anti-RBD (b) antibodies to elicit antibody-dependent complement deposition (ADCD) was measured as the ability of 1 mg/ml of IgG to fix complement on target cells. The Kruskal-Wallis test was used for statistical analysis. Horizontal dotted lines indicate the maximum values from the SARS-CoV-2 negative-control group. (c and d) The ability of anti-S1 (c) and anti-RBD (d) antibodies to elicit antibody-dependent cellular phagocytosis (ADCP) was measured as the ability of 1 mg/ml of IgG to mediate phagocytosis of S1 and RBD antigen-coated beads. The Kruskal-Wallis test was used for statistical analysis. Horizontal dotted lines indicate the maximum values from the SARS-CoV-2 negative-control group. (e) Comparison between the fraction of nonhospitalized and hospitalized COVID-19 patients whose antibodies elicit anti-RBD-specific ADCP with values higher than background (maximum value from the SARS-CoV-2 negative-control group). The chi-square test was used for statistical analysis. (f to i) The ability of anti-S1 (f and g) and anti-RBD (h and i) antibodies to elicit antibody-dependent cell-mediated cytotoxicity (ADCC) was estimated by NK cell degranulation and intracellular cytokine (TNF-α [f and h] or IFN-γ [g and i]) production after exposure of 100 μg/ml of IgG to S1- and RBD-pulsed target cells. The Kruskal-Wallis test was used for statistical analysis. Horizontal dotted lines indicate the maximum values from the SARS-CoV-2 negative-control group. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, not significant.