Early colonization of the spleen by DCs. Paraffin sections (37°C) of spleens from neonates at days 1 (A-B), 3 (C), and 7 (D-E) and adult mice (F) as indicated were labeled for CD11c DCs (red) together with B220 B cells (purple) or CD3 T cells (blue). B cells first appear around the central arteriole (CA) with a ring of DCs (A). Rare T cells are seen at day 1 (B), but at day 3 they are much more numerous and clearly organized around the central arteriole mixed with DCs (C). At day 7, multiple T-cell zones are found and DCs are clearly visualized in the white and red pulp (D-E) as in adult spleen (F). Original magnifications, × 500 (B), × 250 (A,C-D), and × 125 (E-F).