T-cell recognition of gluten peptides #19 and #25.
The identified TG2 peptide substrates VPVPQLQPQNPSQQQPQEQVPL (peptide #9), PHQPQQQVPQPQQPQQPF (peptide #19), SHQQQPFPQQPYPQQPYPS (peptide #25) and SFPQPQPQQPQQPS (peptide #30) were tested together with a panel of synthetic epitope peptides for recognition by three T-cell lines, TCL.BW.CD-E (A), TCL.497.C.1.3 (B), and TCL.422.02.2.4 (C), generated from biopsies of HLA-DQ2.5-positive celiac disease patients. The sequences of the other synthetic peptides tested were|: DQ2-α-I, QLQPFPQPELPY; DQ2-α-II, PQPELPYPQPQLPY; α33mer, LQLQPFPQPELPYPQPELPYPQPELPYPQPQPF; DQ2-γ-I, pyroglutamic acid-PQQPQQSFPEQQRP (in A), pyroglutamic acid-PEQPQQSFPEQERP (in B and C); DQ2-γ-II, GIIQPEQPAQL; DQ2-γ-III, FPEQPEQPYPEQ (in A), FPQQPEQPYPQQ (in B and C); DQ2-γ-IV, FSQPEQEFPQPQ; DQ2-γ-VI, PEQPFPEQPEQ; DQ2-γ-VIIa, TEQPEQPFPQP; DQ2-γ-VIIb, FPQPEQEFPQPQ; DQ2-γ-III/DQ2-γ-VI, LQPEQPFPEQPEQPYPEQPQ; γ23mer, EQPFPEQPEQPYPEQPEQPFPQP; ω17mer, QPQQPFPQPEQPFPWQP. Note that peptides #25 and #19 were tested at different concentrations. The α33mer peptide was tested at 2 µM while the other peptides were tested at 10 µM. Responses were measured in a proliferation assay by the incorporation of 3H-thymidine (counts per minute (CPM)×103). The dashed line indicates two-fold background proliferation observed with medium only. Peptides #25 and #19 were tested in triplicates; other antigens were tested in duplicates. Error bars indicate the standard error of mean. The experiment was repeated twice. The HLA-restriction of the T-cell line TCL.422.02.2.4 was assessed by blocking recognition of peptide #25 using anti-DR, anti-DQ and anti-DP specific monoclonal antibodies (D). Similar results were obtained for T-cell line TCL.497.C.1.3.
