PATIENTS WITH CHRONIC LGL-PROLIFERATIVE DISEASE EXPRESS HIGH MITOGEN-INDUCED CELLULAR CYTOTOXICITY WHICH MAY BE PARTIALLY MEDIATED BY SOLUBLE CYTOLYTIC MOLECULES

Natural killer cell activity (NKa) and mitogen-induced cellular cytoto xicity (MICC) of peripheral blood mononuclear cells (PBMC) were studie d in five patients with chronic LGL-proliferative disease (LGL-PD) of the CD3+, CD8+, CD57+ phenotype. Both assays were performed under the same experimental conditions except that cultures for MICC contained p hytohemagglutinin (PHA) at varying concentrations. Cytotoxicity was as sessed against K562 cell targets using the 18 hours 51-chromium releas e assay. We found that LGL-PD lymphocytes of the aforementioned phenot ype express low NKa but high MICC. Furthermore, supernatants derived f rom patients' PMBC cultures stimulated with PHA, displayed cytolytic p roperties comparable to those of normal lymphocytes. The findings indi cate that MICC may be mediated, at least partially, by humoral cytolyt ic molecules. We concluded that LGL-PD lymphocytes are unable to expre ss natural cytotoxicity but they have not lost the cytolytic machinery necessary for the destruction of sensitive target cells.