Fig. 3: Humoral and B cell immunity during Omicron and Delta breakthrough infection.

a Identification of B cells that bind Spike but not RBD (Spike⁺RBD⁻ B cells) or bind both Spike and RBD (Spike⁺RBD⁺ B cells) in total B cells from three individuals: Healthy Donor (HD), Omicron BTI and Delta BTI. b Quantification of Spike-binding and RBD-binding B cells. Left: Absolute frequency of Spike-binding and RBD-binding B cells. Middle: serum levels of anti-RBD IgG (BAU/ml). Right: Relative frequency of anti-RBD to spike-specific B cells. Ratio of RBD-binding B cells (see top region in a.)/total Spike-binding B cells is shown. c Biplot showing ex vivo profile of Spike⁺RBD⁻ and Spike⁺RBD⁺ B cells during BTI. Top: frequency of CD38 expression in Spike⁺RBD⁻ vs Spike⁺RBD⁺ B cells. Bottom: frequency of CD38^HiCD71⁺ plasmablasts in Spike⁺RBD^- vs Spike⁺RBD⁺ B cells. HD (blue), Omicron BTI (green) and Delta BTI (red) are shown. d Phenotype of Spike-binding B cells. Visualization by tSNE-plot of selected markers as indicated (bottom two rows) in total B cells and location of Spike-binding (Spike⁺) B cells (top row) in HD, Omicron BTI, Delta BTI and aggregated donors (20 000 cells from two individuals per group, total = 120 000 cells). Each marker is visualized by a cold to hot heatmap. e Quantification of anti-Spike antibody secreting cells (ASC). The frequency of specific markers for ASC among B cells (CD38, IRF4, CD71, BLIMP-1) are shown for Total B cells (blue) and Spike-binding B cells. f Characterization of Spike-binding B cells. A heat-plot shows the phenotype of Spike-specific B cells in the three groups. The normalized frequency of each marker is displayed and automatic hierarchical clustering of Spike-binding B cells for each patient is shown. Mann–Whitney test P values are shown for (b) and (e). See also Supplementary Fig. 7.