Sn is expressed specifically on resident macrophages in various human tissues.

Cryostat sections measuring 6 μm from bone marrow (A), spleen (B), reactive lymph node (C), liver (D), colon (E), and lung (F) were stained immunocytochemically with HSN1 mAb. Macrophage populations were stained specifically in all tissues. In bone marrow (A), the stellate processes of resident bone marrow macrophages (arrows) are evident. In the spleen (B), strong staining is present on perifollicular macrophages with weaker staining in the red pulp (RP). Tingible body macrophages within the follicle (F) are not labeled. In reactive lymph node (C), sinusoidal perifollicular macrophages are intensely stained, but no labeling is seen in the follicles (F). In the liver (D), the sinus lining Kupffer cells are labeled. In the colon (E), macrophages in the lamina propria are intensely labeled. In the lung (F), alveolar and interstitial macrophages are positive for Sn. Bars correspond to 50 μm (A) or 100 μm (B-F).