In vivo efficacy of IgA2 antibodies against CD20. (A) Schematic experimental overview of the short intraperitoneal (IP) model. (B) Absolute quantification of EL4-CD20 cells after intraperitoneal injection of the indicated CD20 IgA2 antibodies (100 µg per mouse). (C) Absolute quantification of intraperitoneal Ly6G⁺ granulocytes after treatment with the indicated CD20 IgA2 antibodies. (D) Schematic overview of the adoptive transfer model. (E) Ratio of labeled CD20-Tg/NTg splenic B cells after treatment of pegylated–granulocyte colony-stimulating factor–primed CD89-Tg or NTg mice with the indicated CD20 IgA antibodies (250 µg per mouse). (F) Ratio of labeled CD20-Tg/NTg B cells using CD89-Tg or NTg mice that did (CVF⁺) or did not (CVF⁻) receive intraperitoneal cobra venom factor (CVF) to deplete complement. Mice were treated with an unmodified (IgA2) or a PCD-impaired variant (IgA2 V11L) of OBI-IgA. (G) Schematic experimental overview of a syngeneic human CD20 Tg B-cell depletion model. (H) Quantification of remaining B cells after repeated treatment with OBI-IgA2, as indicated in (G), using CD89-Tg mice (left panel) or NTg mice (right panel). Results are presented as scatter dot blots (A-D) and as mean ± SEM of 6 mice per group (E). Statistical analyses were performed using 1-way ANOVA. *Significant difference vs PBS, unless indicated otherwise. ^#Significant difference OBI treatment NTg vs OBl treatment Tg. ^§Significant difference between different IgA2 antibodies. Horizontal line indicates the median. Ab, antibody; G-CSF, granulocyte colony-stimulating factor; h, human; n.s., not significant; Wt, wild-type.