Characterization of candidate endogenous peptides that stimulate Be-specific T cell hybridomas. (A) Dose–response curves to stimulatory peptides identified from the biometric analysis of T cell hybridoma AV22 are shown. Equal numbers of AV22 cells and DP2.21 antigen-presenting cells were mixed with 75 µM BeSO4 and highly purified peptides. IL-2 secretion was measured by ELISA after 22 h of culture, and data are plotted as the percentage of maximum IL-2 secretion against concentration of peptide in the presence of BeSO4. EC50 values (mean ± SEM nM) for mimotope-4 and each human peptide from four independent experiments are shown. Note that error bars have been left out for viewing clarity. (B) AV22 response to antigen-presenting cells expressing HLA-DP2 with spectrin and plexin peptides covalently attached to the N terminus of the β-chain. Percentage of maximum IL-2 secretion versus the number of antigen-presenting cells added per well is shown. Results are representative of three independent experiments. (C) IL-2 response (mean ± SD pg/ml) of AV22 and dengue virus–specific hybridoma DV-13 to plexin proteins presented by an EBV-transformed B cell line derived from CBD patient 1332 is shown. Plexin proteins (A1, A2, A4, and C1, all at 100 µg/ml) were added in the presence and absence of 75 µM BeSO4. Control peptides, mimotope-4 and dengue viral peptide, were added at 100 nM and 20 µM, respectively. Representative results from three independent experiments are shown. (D) Dose–response curves of AV22 to plexin A1, A2, and A4 proteins presented by EBV-transformed B cells in the presence of 75 µM BeSO4 are shown. Representative results from three independent experiments (mean IL-2 ± SD pg/ml) performed in triplicate are shown.
