Non-lymphoid DLL1⁺ cells are located in the splenic MZ. Confocal imaging analysis of spleen sections from children stained with fluorescence-conjugated anti-DLL1 (green), anti-IgD (red), and anti-CD27 (blue; original objective lens magnification 40×). (A) One representative image (out of three splenic samples analyzed) of a GC surrounded by densely distributed IgD⁺CD27⁻ naive cells forming the corona and the MZ at the periphery, occupied by CD27⁺IgD^low B cells (lightly colored in purple; splenic section of a 4-yr-old child; bar, 150 µm). (B and C) Selected areas of splenic sections (from 2- and 4-yr-old children, respectively), illustrating the presence at various density of DLL1⁺ cells in the MZ. Note the complete absence of DLL1 staining in the corona (bars, 50 µm). The insets i and ii show, respectively, a four- and threefold magnification of DLL1-positive cells that are in close contact with IgD^high cells in the MZ (bars, 30 µm). Co, corona; RP, red pulp.