Targets expressing host type MHC are lysed by activated T cells derived from deletion-deficient chimeras. (A) Thymocytes or splenocytes of indicated origin were stimulated in vitro with approximately the same number of irradiated DBA/2-derived (top panels) or C57BL/6-derived (bottom panels) T-cell–depleted splenocytes in the presence of exogenous IL-2. After 6 days of stimulation, lysis of indicated targets was assessed. (B) As in (A), but in vitro stimulation of splenocytes was performed with or without added IL-2, as indicated. E/T ratios were corrected for anti-CD3ɛ antibody redirected lysis of P815 targets as described in Materials and Methods.