Differences in antigen recognition and cytolytic activity of CD8(+) and CD8(−) T cells that express the same antigen-specific receptor

CD8(+) and CD8(−) T cell lines expressing the same antigen-specific receptor [the 2C T cell receptor (TCR)] were compared for ability to bind soluble peptide-MHC and to lyse target cells. The 2C TCR on CD8(−) cells bound a syngeneic MHC (K(b+))-peptide complex 10–100 times less well than the same TCR on CD8(+) cells, and the CD8(−) 2C cells lysed target cells presenting this complex very poorly. Surprisingly, however, the CD8(−) cells differed little from CD8(+) cells in ability to bind an allogeneic MHC (L(d+))-peptide complex and to lyse target cells presenting this complex. The CD8(+)/CD8(−) difference provided an opportunity to estimate how long TCR engagements with peptide-MHC have to persist to initiate the cytolytic T cell response.