[The effect of corticosteroid on lymphokine-activated killer (LAK) activity and the change of membrane antigen phenotype on PBMC after IL2 incubation with reference to the evaluation in vitro].

In the treatment of human cancer, the efficacy of the adoptive transfer of lymphokine-activated killer (LAK) cells combined with interleukin 2 (IL2) has been emphasized. However, administration of large doses of IL2 may cause significant adverse effects, such as "capillary leak syndrome". Moreover, the administration of corticosteroid may reduce the toxicity of IL2. However the efficacy of adoptive immunotherapy is abrogated by the administration of corticosteroid. In this context, the effect of corticosteroid on LAK activity and the change of membrane antigen phenotype on PBMC (peripheral blood mononuclear cells) was studied in vitro by using methylprednisolone (M-PSL). LAK cells were induced from PBMC, which had been separated from the peripheral blood of normal donors, and incubated with IL2 for 4 days. LAK activity was measured in a 4 h chromium release assay against K-562 cell and Daudi cell. The suppression of LAK activity by M-PSL depended on both concentration and working period of M-PSL. This inhibition was recognized even at rather low densities, such as 0.5 nmol/ml M-PSL. And the proliferation of PBMC after IL2 incubation, which was measured by incorporation of [3H]TdR, was reduced dose-dependently by M-PSL. In contrast, pretreatment within 24 hours of PBMC with M-PSL resulted in no effect on LAK activity. Furthermore M-PSL had no effect when added directly to a 4 h chromium release assay. The analysis of membrane antigen phenotype on PBMC was performed by the direct immunofluorescence method using FITC-labeled monoclonal antibodies. The proportions of T cells and NK cells, which were justified as precursors of LAK cells, increased after IL2 incubation both with and without M-PSL. Therefore no effect of M-PSL was confirmed in those circumstances. The ratio of HLA-DR (+) cells increased after IL2 incubation without M-PSL, while M-PSL reduced expression of this antigen. In contrast, IL2 receptor (CD25)(+) cells, markers of T cell and NK cell activation, significantly increased after IL2 incubation with or without M-PSL. These results suggest that the inhibitory effect of M-PSL on LAK activation was caused not by preventing a triggering process of activation of precursor cells, but by a possible inhibition of proliferation, though other effects of corticosteroid remain to be elucidated. Also, it is emphasized that caution should be exercised in the administration of corticosteroid in adoptive immunotherapy because of the inhibitory effect induced by M-PSL.