Border of white pulp in spleen (mouse)

Monoaminooxidase (enzyme histochemistry on frozen section) with Nitro-BT as staining substrate resulting in a blue formazan precipitate. Despite the general activity of most cells in the spleen, the border cells or so-called metallophilic cells (1) or dendritic antigen-presenting cells (APC) show the most outstanding positive reaction for this oxidative enzyme. These metallophilic macrophages are located strategically for antigen capturing and/or phagocytosis adjacent to the B cells in the follicle. These cells can also be stained positively with anti-CD169 with the antibody ED3. At (2) the faintly negative reacting central artery. (3) indicates the PALS area (T cells) around the arteriole, while (4) points to the germinal centre of the follicle (B cells). The red pulp is marked by (5).