MHC phenotype and killing specificity of CTL reisolated from BMT recipients. C57BL/6 mice were transplanted with BM from B10.A(4R) mice and injected the following day with mdm100-specific CTL isolated from BALB/c mice. (A) After 4 weeks, mice were killed and cells from lymph nodes were stimulated in bulk cultures as described in Fig 3, resulting in mdm100-specific CTL activity similar to that seen in Fig 3C. (B) After 4 weeks, mice were killed and cells from lymphoid tissues were analyzed in LDA assays as described in Fig 5. The CTL bulk cultures (A) or the CTL expanded from positive wells of LDA assays (B) were then double-stained with PE-labeled CD8 antibodies and antibodies specific for K^b, K^k, and L^d. Staining with the anti-class I antibodies was detected with FITC-labeled secondary antibodies (see Materials and Methods). Shown is the staining of gated CD8 cells with the indicated anti-class I antibodies. Similar results were obtained in independent experiments. (C and D) CTL killing of RMA-S target cells coated with mdm100 and of RMA lymphoma cells expressing naturally processed mdm100. (C) Analysis of CTL used for injection into BMT mice and (D) analysis of CTL rescued from mice and expanded from LDA plates as in (B).