CD137-mediated depletion of HLA-B*0702 mismatch-reactive T cells. CD8 T cells of naive donor 203 were weekly stimulated with haploidentical MZ1257-RCC cells in allo-MLTC (for HLA types see Table 1). (A) IFN-γ ELISPOT results of day 18 MLTC responders tested against MZ1257-RCC and against K562 transfectants expressing the MZ1257-RCC–encoded HLA mismatch alleles A*0301, B*0702, or Cw*0702. (B) After 24 hours of incubation with K562-B*0702 transfectant cells, day 22 MLTC responders were depleted of allo-B*0702–reactive T cells using either the CD137/CD65 or the CD137 approach (latter not shown). Flow cytometry results indicate percentages of CD137^pos CD8 T cells. Residual CD137 expression in the CD137/CD65^neg subset (ie, 0.7%) was equivalent to day 22 background isotype control (0.7%, not shown). (C) Immediately (day 22) after separation, the CD137^neg and CD137/CD65^neg fractions (white bars), the CD137^pos and CD137/CD65^pos fractions (gray bars), and the MLTC control-stimulated exclusively with MZ1257-RCC (black bars) were analyzed for reactivity in IFN-γ ELISPOT assay. (D) The CD137^neg, respectively. CD137/CD65^neg fractions (white bars) and the MLTC control (black bars) were retested in IFN-γ spot assay on day 33 after simultaneous stimulations with MZ1257-RCC on day 22 and day 29.