ABERRANT EXPRESSION OF MACROPHAGE-ASSOCIATED ANTIGENS (CD68 AND KI-M1P) BY SCHWANN-CELLS IN REACTIVE AND NEOPLASTIC NEURAL TISSUE - LIGHT-MICROSCOPIC AND ELECTRON-MICROSCOPIC FINDINGS

The monoclonal antibodies KP1 (CD68), PG-M1 (CD68), an M1P can be used to detect normal and neoplastic monocytes/macrophages in formalin-fix ed, paraffin-embedded tissue. However, systematic investigations under taken on various tissues have revealed that reactivity with these anti bodies is also found in a few cells that do not belong to the mononucl ear phagocyte system. The immunoreactivity of normal, reactively alter ed, and neoplastic Schwann cells with these antibodies was investigate d using intact peripheral myelinated nerves, nerves exhibiting Walleri an degeneration, traumatic neuromas, appendixes with neurogenic append icopathy, granular cell tumors, neurofibromas, and neurogenic sarcomas . The results obtained by light microscopy showed that Schwann cells o f nerves with Wallerian degeneration and those in traumatic neuroma, n eurofibroma, and granular cell tumor exhibit intracytoplasmic immunore activity, which is usually intense, with KP1, Ki-M1P, and PG-M1, but n ormal myelinated nerves, neurogenic sarcoma, and Schwann cells in neur ogenic appendicopathy do not react with these antibodies. No Schwann c ells were stained by MAC387 or anti-lysozyme. The site of immunoreacti vity with these antibodies was also investigated by electron microscop y. One of the granular cell tumors and macrophages in lymphoid tissue were investigated by the immunogold technique using both pre- and post embedding methods. In granular cell tumor the reaction product was loc ated in phagolysosomes; in macrophages it was found in phagosomes and/ or lysosome-like granules. Our findings therefore indicate that immuno reactivity with KP1, Ki-M1P, and PG-M1 can also be expected in cells t hat do not belong to the mononuclear phagocyte system if they exhibit phagocytosis and/or autophagy.