FIG. 1.

TAg-specific cytotoxicity mediated by freshly prepared CD8⁺ cells or by spleen cell bulk cultures prepared from mice immunized with different protocols. TAL or spleen cells were recovered from mice pretreated as follows: twice immunized with TAg, challenged with mKSA cells, CD8⁺ TAL prepared from the peritoneal cavity 8 days after challenge (filled diamonds; the reduced effector/target ratio is due to the poor yield of CD8⁺ TAL from this group of five mice); TAg immunized, challenged with mKSA cells, CD8⁺ spleen cells prepared on day 8 (open diamonds); TAg immunized, challenged with mKSA cells, restimulated in the presence of TAg-expressing cells 4 weeks after challenge (filled circles); SV40 immunized (once), restimulated in the presence of TAg-expressing cells 2 weeks after immunization (filled squares); TAg immunized, restimulated 4 weeks after immunization for three weekly cycles (inverted filled triangles); TAg immunized, restimulated once 4 weeks after immunization (filled triangles); and naive, stimulated once in the presence of TAg-expressing cells (open circles). Lytic activity against MHC-matched, non-TAg-expressing MethA cells or against MHC-mismatched, TAg-expressing SV40-transformed C57BL/6 fibroblasts was below 7% (data not shown).