Elongated peptides comprising the TEL-AML1 epitope cannot evoke CD8+ T-cell responses. ABabDII mice were immunized subcutaneously in the tail base with 30-mer peptides, comprising either (A) the native TEL-AML1 sequence, (B) the anchor-modified TEL-AML1-9V sequence, or (C) the anchor-modified gp100, mixed with CpG oligodeoxynucleotides, PBS, and IFA. In the cases of the TEL-AML1 native and anchor-modified peptide, some of the mice were additionally boosted after 2 weeks with the corresponding peptides. Spleen and draining LNs were isolated 10 days after the immunization, or boosting. The cells were in vitro restimulated overnight either with 10−6M corresponding nonamer peptide (TEL-AML1, TEL-AML1-9V, or gp100), an irrelevant peptide (NY-BR-1) or with anti-CD3/CD28 antibodies. The cells were stained for CD8, as well as for CD3 and IFN-γ intracellularly and analyzed by flow cytometry. Events shown are gated on CD3+CD8+ lymphocytes; numbers indicate percentages of cells in the respective quadrants. In the case of gp100 one representative of 3 analyzed mice is shown, and in the cases of the TEL-AML1 anchor-modified, as well as the native peptide, 1 representative of 6 analyzed mice is shown.
