Effect of rituximab infusion on the frequencies of CD79a⁺ B cells in tissues. Panels A through F demonstrate the rituximab effect on LN CD79a⁺ B cells in a RM with complete B-cell depletion in tissues (A-C) versus a RM with incomplete B-cell depletion in tissues (D-F). LNs were collected before (day −7 pi; A,D) at 28 days pi (B,E) and at day 300 pi (C,F). Panels G through R demonstrate the rituximab effect on intestinal CD79a⁺ B cells from both lamina propria (LP; G-L) and Peyer patches (PP; M-R). Slides were examined with a Leica DMLB microscope (Leica Microsystems, Wetzlar, Germany) using the following objective lenses and numeric apertures: N PLAN 5×/0.12 (panels A-F); N PLAN 10×/0.25 (panels M-R); and N PLAN 20×/0.4 (panels G-L). Images were acquired with Spot Insight color 3.2.0 software (Diagnostic Instruments, Sterling Heights, MI) and processed with Adobe Photoshop Elements version 3.0 (Adobe Systems, San Jose, CA).