Histological analysis of T and B cells in PLN, PP, and spleen in +/+ and plt/plt. PLN (a-d), PP (e-h) and spleens (i-l) were from DDD/1-+/+ and DDD/1-plt/plt. Spleens from BALB/c-+/+ (m,n) and BALB/c-plt/plt (o, p) were also examined. Cryostat section was treated sequentially with 30H12 (anti-Thy1.2) or RA3-3A1/6.1 (anti-B220) MoAb, biotinylated rabbit antirat IgG (Vector) polyclonal Ab, and horse radish peroxidase-conjugated streptavidin (Zymed), and visualized with 3, 3'-diaminobenzidine tetrahydrochloride (Dojindo). The sections were counterstained with Gill's hematoxylin (Polysciences) and photographed under a microscope. Bar indicates 400 μm.