Where does the antigen of cutaneous sarcoidosis come from?

The antigen pathway of cutaneous sarcoidosis remains obscure. We have investigated topographic involvement of inflammatory cells and lymphatic vessels.

Eleven cutaneous biopsies from eight patients were studied, along with controls from other granulomatous disorders and various skin lesions. Markers for lymphocytes, dendritic cells (DCs), and lymphatic vessel endothelial cells were detected using immunohistochemistry.

S100(+) and CD1a(+) immature DCs (Langerhans cells) occurred more frequently within the epidermis, whereas S100(+), fascin(+), or CD83(+) maturing DCs occurred more frequently beneath the epithelium in cutaneous sarcoidosis cases than in controls (e.g. CD83, cutaneous sarcoidosis vs. other granulomatous disorders: r = 0.557, p = 0.011). Fascin(+) and CD83(+) mature DCs were often closely attached to CD3(+) T-lymphocytes around dermal granulomas. D2-40(+) lymphatic vessels were often found surrounding dermal granulomas, especially those located in the deeper dermis, in contrast to fascin(+) blood vessels.

Antigen-capturing by immature DCs seems to take place initially in the epidermis, followed by maturation of DCs. These mature DCs may present the processed antigen to T-lymphocytes that cause dermal granulomas either in the interstitium of the upper dermis, or in or around lymphatic vessels of the lower dermis. Environmental antigen could be verified by skin test.