NASAL T NK CELL LYMPHOMAS COMMONLY EXPRESS PERFORIN AND FAS LIGAND - IMPORTANT MEDIATORS OF TISSUE-DAMAGE/

Aims: Two molecular mechanisms of T/natural killer (NK) cell-mediated cytotoxicity, one perforin based and the other Fas based, have been de monstrated, and both systems induce cytotoxicity in the target cells, The Fas-based mechanism involves the transducing molecule Fas and its ligand (FasL). In addition, perforin and/or Fast are also expressed in the cytotoxic T/NK cells, This study was thus designed to investigate the Fas and perforin pathways of the cylotoxic T/NK lymphoma cells in the nasal cavity. Methods and results: Eight patients with nasal lymp homa were analysed using immunohistochemical staining methods. Two cas es were CD3+ CD56+ (T/NK cell) type, and six were CD3-CD56+ (NK cell) type, All cases showed Epstein-Barr virus genomes by in-situ hybridiza tion, In addition, all cases showed the expression of TIA-1 (GMP-17), which is a marker of cytotoxic T and NK cells, Fast was expressed in t he majority of the lymphoma cells and some histiocytes, while Fas was found in lymphoma cells and many non-neoplastic cells, In addition, th e expression of perforin was detected in almost all lymphoma cells, In the double stainings. lymphoma cells expressed both Fast and perforin , Based on these findings, both the perforin- and Fas-based pathway of the cytotoxic T/NK lymphoma cells are thus considered to play an impo rtant role in the clinical features, Conclusions: Tissue damage is a c ommon morphological feature in nasal T/NK cell lymphoma. The above fin dings therefore the theory that issue damage is due to the cytotoxicit y of T/NK lymphoma cells as well as to angiocentricity.