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.