Detailed characterization of PLNs within spleens from ITP patients. Sections from 4 spleens (3 ITP and 1 control) were examined by double immunofluorescence staining: CD20 (red) with IgD (green), CD1c (green), CD27 (green), or IgM (green). (A) PLN (ITP) and (B) GC (control). The white outline indicates the location of the structures, PLNs and GCs, determined by IgM staining. The presence of T cells in PLNs was analyzed by CD3 (green) and CD20 staining. The arrows designated a T-cell area (B). Control for nonspecific binding was performed on spleen sections using FITC-secondary antibodies and CD20 (red). The sections were analyzed by confocal microscopy using a Zeiss LSM 710 confocal or a Zeiss Axio Imager Z1 fluorescence microscope (×200 magnification; Carl Zeiss).