Figure 1.

Peptide binding to K^d. RMA/S K^d cells incubated overnight at 26°C were incubated for an additional hour with the indicated concentration of peptide and BFA (5 μg/ml), and then at 37°C for 2 h (left). Alternatively, cells were incubated with 10 μM peptide and BFA, extensively washed, and then incubated at 37°C for the indicated time in the absence of peptide (right). The amount of cell-surface K^d was determined using the fluorescein-conjugated mAb SF1.1.1 (PharMingen, San Diego, CA). The concentration of peptide required for protection of one half of the K^d molecules was determined by linear extrapolation of the mean channel fluorescence values.