Spontaneous lysis and HLA-class I expression of NHL B-cell lines by polyclonal Vγ9Vδ2 T lymphocytes. Cytotoxic activity of two independent polyclonal Vγ9Vδ2 T cell lines (cell line 1, dark bars; cell line 2, clear bars) toward 15 NHL B-cell lines and one Hodgkin’s lymphoma cell line were tested in vitro. The data represent the average of at least three independent experiments. Polyclonal cytotoxic cell lines were obtained by stimulation of PBMC from healthy donors with mycobacterial phosphoantigen (3fbPP) in the presence of IL-2. After 15 to 20 days, Vγ9Vδ2 T cells account for 90–99% of the cells. Target cell lines are arbitrarily presented in decreasing order of global (sum of lysis by the two Vγ9Vδ2 cell lines) sensitivity to Vγ9Vδ2 CTL. (E/T = 20/1). Evaluation of the expression of HLA-class I molecules at the surface of each target is given by the mean fluorescence intensity (MFI) of the whole cell population previously stained with W6/32 and GAM-FITC mAbs. MFI values were obtained by subtracting MFI of the cell population stained with isotypic control IgG2a antibody and GAM-FITC. EBV status is presented according to cell lines referenced in Table 2.