Cytotoxicity mediated by PE-9 cells against LSA and other targets. PE-9 cells were tested for lytic activity against various ⁵¹Cr-labeled targets. PE-9 CTLs were activated with MoAbs against the TCR before cytotoxicity assay, or the MoAbs against the TCR were added while performing cytotoxicity assays to facilitate activation of T cells and redirected lysis. The MoAbs used were against αβTCR in A, C, and E and against CD3 in B, D, and F. In A and B, LSA wild-type (wt) and a clone expressing higher levels of Fas (LSA Fas⁺) were used as targets. In C and D, LPS blasts from the spleens of +/+ and lpr/lpr mice were used. In E and F, L1210 Fas⁺ and Fas⁻ transfectants were used as targets.