T-zone histiocytes in granulomatous skin diseases.

We investigated the distribution of T-zone histiocytes by immunohistochemical demonstration of S-100 protein in granulomatous skin diseases (granuloma annulare, 8 cases; necrobiosis lipoidica, rheumatoid nodule, sarcoidosis, lupus vulgaris, and foreign-body granuloma; 5 cases each). T-zone histiocytes were regularly found in the lymphohistiocytic mantle, but also occasionally between epitheloid cells. Our results show that, besides the monocyte-macrophage system, T-zone histiocytes consistently contribute to the formation of cutaneous granulomas. These findings may indicate a role of delayed-type hypersensitivity.