Lectin histochemistry of the spleen: A new lectin visualizes the stromal architecture of white pulp and the sinuses of red pulp

The subcompartmentalization of the white pulp in the spleen is the result o f interactions of specific resident stromal cells and migrating subtypes of lymphocytes. Because carbohydrate residues of cell membranes and extracell ular matrices are involved in cell-cell and cell-matrix interactions, they were investigated in rat spleen by a broad panel of lectins. Splenic macrop hages, which were also demonstrated by Perls' Prussian blue reaction, were labeled selectively by most mannose-specific lectins and gave the character istic distribution patterns in all splenic (sub)compartments. One recently isolated lectin, Chelidonium majus agglutinin (CMA), visualized predominant ly central arterioles, the reticular meshwork (RM) in the periarteriolar ly mphatic sheaths (PALS), the circumferential reticulum cells limiting PALS a nd follicles, and some follicular dendritic cells (FDCs) in white pulp. The endothelial cells of venous sinuses in red pulp were also labeled by CMA a nd, if frozen sections were used, CMA also labeled the macrophages of the r ed pulp. Compared to CMA, the monoclonal antibody CD11, which can be used o nly in frozen sections, stained almost solely the fibrous (extracellular) c omponent of the RM. Because CMA stains the reticulum cells in particular, i t is better suited to visualize the stromal architecture of splenic white p ulp than the monoclonal antibody. Because CMA can be applied to paraffin-em bedded material, it is a particularly useful tool to study the splenic stro mal architecture in archival material.