Sn is expressed on inflammatory macrophages in rheumatoid synovial membrane.

Cryostat sections of rheumatoid synovial membrane measuring 8 μm were stained immunocytochemically with the mAb HSN1 (A-C) or with the antimacrophage marker CD68 (D). Most cells expressing Sn are located in the intima (inset to panel B), which contain a large proportion of CD68⁺ macrophage-like synoviocytes. In contrast, little if any Sn staining is seen within the T- and B-cell–rich extralymphoid follicles, despite the presence of large numbers of CD68⁺macrophages pervading the tissue (D). Bars correspond to 100 μm.