Immunohistochemical double stainings of human tonsil with the patient-1 scFv. Double stainings with the patient-1 scFv (brown) and antibodies against (A) the plasma cell–specific transcription factor IRF4 (red), (B) the immunoglobulin subclass G (red), and (C) the immunoglobulin subclass A (red). Arrows denote double-stained cells. Images were obtained with an Olympus AX70 microscope equipped with a JVC KY-F70U camera using Diskus v4.28 software. Objectives used were as follows: panels A and B, 20 ×/0.7 NA (total magnification, × 140); panel C, 40 ×/0.95 NA (total magnification, × 380).