Fig. 3. Detection of ADCC-mediating antibodies by measuring NK92.05 degranulation.

(A) Gating strategy for detection of degranulating NK cells: (i) NK92.05-CD16 cells are selected on the basis of size and granularity, (ii) exclusion of doublets, and (iii) selection of LIVE and CD56⁺ cells. Degranulation is measured as percentage CD107a⁺ cells within the NK fraction; PBS coating is included as background control. (B and C) ADCC-mediating antibodies were detected in COVID-19–naive (yellow) and –recovered (blue) donors at the acute, convalescent, post-vaccination 1, and post-vaccination 2 stage (T0, T3, Vx¹3, and Vx²3) against the WT N (B) and S (C) protein. (D) ADCC-mediating antibody reactivity with WT SARS-CoV-2 and VOC B.1.1.7 and B.1.351. These analyses were performed on 25 participants. Time points in (B) and (C) were compared by performing a nonparametric repeated measures Friedman test. Differences between variants were assessed by mixed-effect models. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001. Symbol shapes indicate individual donors and are consistent throughout the figures. Lines indicate mean responses.