CD56(-KILLER-CELL LYMPHOMAS - PRODUCTION OF CYTOLYTIC EFFECTORS AND RELATED PROTEINS MEDIATING TUMOR-CELL APOPTOSIS() PUTATIVE NATURAL)

Apoptosis is a regulated form of cell death that may be triggered by n atural killer (NK) or cytotoxic T cells, which effect target cell lysi s by cytolytic effector and related proteins through complex intracell ular signals. This study was aimed to investigate whether there is sel ective expression of these cytolytic markers in the putative NK-cell l ymphomas and whether there is correlation with zonal tumor cell death in these tumors. Expression of the cytolytic effecters perforin, granz yme B9, and the granule membrane protein TIA1 were examined in 24 puta tive NK-cell lymphomas, 18 postthymic T-cell lymphomas (one case CD8() CD56(+) and three anaplastic large cell lymphomas (ALCL), three T-ly mphoblastic lymphomas, and 20 B-cell lymphomas. Nineteen (79%) putativ e NK-cell lymphomas expressed perforin, and all 24 cases expressed gra nzyme B9 and TIA1. The only CD8(+) CD56(+) postthymic T-cell lymphoma also expressed all three cytolytic markers, two CD8- ALCL expressed TI A1; other postthymic T-cell, T-lymphoblastic, and B-cell lymphomas wer e consistently negative. There was strong correlation between percenta ge perforin-positive cells and zonal tumor cell death. Angioinvasion, in contrast, was present only in a proportion (37%) of these lymphomas despite the frequent presence of zonal tumor cell death (71%). We pro pose that cytolytic effector and related proteins produced by putative NK and some CD8(+) CD56(+) postthymic T-cell lymphomas, probably in c onjunction with other mechanisms, may effect massive tumor cell apopto sis. The frequent expression of cytolytic effector markers in the CD2( +) surface CD3(-) CD56(+) putative NK-cell lymphomas lends further sup port to their probable NK cell origin. Copyright (C) 1997 by W.B. Saun ders Company .