Trogocytosis of B-cell membrane proteins in SLE patients. (A) PBMCs were isolated from blood specimens of 3 treatment-naïve SLE patients and incubated overnight with 10 µg/mL epratuzumab or labetuzumab. The relative levels of CD19, CD22, CD21, and CD79b on B cells posttreatment were measured by flow cytometry. Bars represent mean values. (B) B cells were gated further into CD27⁺ and CD27^– populations before analysis. (C) The levels of CD22, CD19, CD21, and CD79b were measured by flow cytometry on B cells gated from PBMCs that were isolated from 4 SLE patients who had yet to receive any treatment (naïve), 5 patients on active immunotherapy with epratuzumab, and 2 patients on immunotherapy with belimumab. Bars represent mean values. Each sample was evaluated in triplicate.