Similar Ag levels for Tet-TagLuc and 16.113p cells, and similar pMHC affinity for pI and pIV. (A) Histogram shows T-Ag expression measured in T-Ag–negative cells (MCA-205), Tet-TagLuc, and 16.113p tumor cells by intracellular T-Ag staining. One representative of two experiments is shown. (B) The concentration of pI and pIV necessary for yielding 50% binding inhibition (IC₅₀) of the indicator peptides to MHC-I (pI/H2-D^b, pIV/H2-K^b). One representative of three experiments is shown. (C) IFN-γ values obtained by 24-h co-culturing of 10⁵ TCR-I or TCR-IV T cells with indicated numbers of Tet-TagLuc or 16.113p tumor cells. The target cells were incubated with 100 ng/48 h IFN-γ before co-culture. The values are given as percentage of maximum, which was calculated by taking the T cell response to the highest tumor cell number as 100% (maximal value), and then calculating the percentage of for each value as percentage of maximum. One representative of two experiments is shown.