Relative affinities of B6^dom1 (AAPDNRETF) and H-Y (WMHHNMDLI) for D^b. T2D^b (A and B) and RMA-S cells (C and D), precultured at 26°C, were incubated in serum-free medium with various concentrations of synthetic B6^dom1 or H-Y peptide, stained for D^b surface expression, and analyzed by flow cytometry. (A) H2-D^bsurface expression of T2D^b cells incubated alone (dashed line), with 10⁻⁴ mol/L H-Y (solid black line, grey background), or with 10⁻⁴ mol/L B6^dom1 (solid black line). (B) Corrected MFI of T2D^b cells stained with anti-D^b Ab after incubation with graded concentrations of peptides. (C) H2-D^b surface expression of RMA-S cells incubated alone (dashed line), with 10^-4 mol/L H-Y (solid black line, grey background), or with 10⁻⁴ mol/L B6^dom1 (solid black line). (D) Corrected MFI of RMA-S cells stained with anti-D^b Ab after incubation with graded concentrations of peptides. One representative experiment of two is shown.