Tumor antigen-specific CTLs release cytokines and exert cytotoxic activity when incubated in vitro with autologous tumor cells. A. CTLs (1 × 104) were incubated with an equal number of 81–86 (allogeneic tumor, a negative control), 81-86-1203 tumor cells (allogeneic tumor transfected with HLA-Cw1203, a positive control), or LT-391-06 tumor cells (autologous tumor). CTLs and tumor cells were also incubated alone as controls. Cells were incubated overnight at 37°C. Supernatants were analyzed by sandwich ELISA for the presence of IFN-γ and TNF-α. B. The cytotoxic activity of CTLs was analyzed by a 51chromium release assay. Serial dilutions of CTLs (starting from 1 × 104) were incubated with either (1 × 103) LT-391-06 (●) or Daudi (▲, negative control) or K562 (■, negative control).