DISCRIMINATION BETWEEN IMMUNOACCESSORY AND PHAGOCYTIC MONOCYTES MACROPHAGES OF THE SKIN IN PARAFFIN-EMBEDDED TISSUE BY THE MONOCLONAL-ANTIBODY KI-M1P

The variety of functions performed by monocytes and macrophages is ref lected in their phenotypic diversity. Investigation of this complex sy stem is facilitated by Ki-M1P, a new monoclonal antibody which recogni zes a differentiation antigen on monocytes/macrophages in paraffin-emb edded tissues. To test its usefulness as a pan-macrophage marker in th e skin, we immunohistochemically analysed paraffin-embedded biopsy mat erial from seven healthy individuals and 190 patients with a variety o f dermatoses. Immunoreactivity was compared with results obtained with the antibodies KP-1, MAC-387, UCHL-1 and S-100. In normal skin, epide rmal Langerhans cells were Ki-M1P-. Strong expression of this marker w as detected on spindle-shaped as well as dendritic perivascular and in tervascular macrophages. Pathological reaction forms such as giant cel ls and epithelioid cells in granulomatous dermatoses were also Ki-M1P. The high specificity of Ki-M1P is reflected in the lack of reactivit y with tumour cells in non-monocytic neoplasms and Langerhans cell his tiocytosis. Thus, Ki-M1P is a useful marker for skin macrophages, disc riminating between the immunoaccessory and the phagocytic compartments .