Monoclonal antibodies distinguish macrophages and epithelioid cells in sarcoidosis and leprosy.

Existing anti-macrophage monoclonal antibodies are unable to differentiate between macrophages and epithelioid cells. In search of more precise reagents, we have applied recently developed antibodies to lesions of sarcoidosis and leprosy. UCHM1 and Leu-M3 stained both granulomas and surrounding histiocytes. However, in lesions with epithelioid granulomas there was a clear distinction between cells identified by RFD9 (epithelioid and giant cells) and RFD7 (macrophages in the surrounding mantle and normal tissue), whereas macrophages in the non-hypersensitivity granulomas of lepromatous leprosy were labelled by both the latter antibodies. In lung biopsies, alveolar macrophages were also labelled by both RFD7 and RFD9. These reagents may be useful for studying pathogenic mechanisms in granuloma formation.