These procedures were carried out as described previously (22 (link), 23 (link)). Antibodies used for staining: purified rat anti-mouse CD35 (8c12; BD Biosciences), biotin-anti-CD45.2 (104; BD Biosciences), Alexa Fluor 555-conjugated goat polyclonal anti-rat (Invitrogen), Alexa Fluor 488-Streptavidin (Invitrogen), Alexa Fluor 647-conjugated rat Ab to mouse IgD (11–26C.2a; Biolegend). Mounted sections were imaged with 10 × and 20 × objective on a Nikon Eclipse Ti-S microscope.