Dual targeting with proteasome inhibitor and CoB (belatacept and anti-CD40 mAb [2C10]) successfully promoted desensitization. (A) Timing and dosing of bortezomib, belatacept, and anti-CD40 mAb’s for desensitization and biopsy scheme for treated animals. (B) DSA from T-cell flow-cytometric cross-matching of sensitized animals before and after dual targeting treatment. DSA levels are expressed as mean channel fluorescent intensity (MFI) ratio. Serum DSA level was significantly reduced after CoB treatment (pre- vs posttreatment). (C) Visualization of BM PCs. Dual targeting treatment significantly affected CD19⁺CD20⁻CD38⁺ cells in the BM biopsy after dual targeting treatment. Representative flow plot and percentages of the CD19⁺CD38⁺ PC population in the BM at the indicated time points (pre- vs posttreatment). (D) Tfh cells were traced with PD-1 and inducible T-cell costimulator (ICOS) from the LN biopsies. LN-Tfh cells showed a significant reduction after dual targeting treatment. Representative flow plot (CD4 gated) and percentage of the ICOS⁺PD-1^high cell population in the LN. (E) A strong trend of reduction of CXCR5⁺BCL-6⁺ B cells in the LN biopsy after CoB treatment. Representative flow plot (CD20 gated) and percentage of the CXCR5⁺BCL-6⁺ GC B-cell population in the LN. (F) Proliferated isotype switched B cells before and after CoB treatment. Ki67⁺IgG⁺IgD^loCD20⁺ B cells in the LNs were greatly reduced after CoB treatment. (G) Immunofluorescent analysis of LN including B-cell follicles and GC staining for Ki67 (green), CD20 (red), and CD3 (blue). Original magnification ×200. Quantification of positive fluorescence signal of CD20 for B-cell follicle, and Ki67/CD20 for proliferating GC. Data represent the mean ± standard deviation (SD) of 4 monkeys per group. NS, nonsignificant.