Tc1 and Tc2 populations mediate cytotoxicity when stimulated through the TCR. Tc1 and Tc2 populations were used as effector cells in standard 4-hour ⁵¹Cr-release assays at the stated E:T ratios with the murine leukemia/lymphoma cell line L1210 as target. Tc1 and Tc2 populations were either taken directly from culture (day 13) or restimulated with bone marrow–derived stimulator cells on day 10 of culture. The L1210 target was used either unmodified or TNBS-modified and then incubated with a bispecific antibody to TNBS and the human TCR. A, Tc1 or Tc2 cells restimulated with alloantigen and tested against the TNBS-modified target; B, Tc1 or Tc2 cells taken directly from culture and tested against the TNBS-modified target; C, Tc1 or Tc2 cells restimulated with alloantigen and tested against the unmodified target; D, Tc1 or Tc2 cells taken directly from culture and tested against the unmodified target.