Peptides (12-mers) with single or multiple amino acid substitutions compared
with HPA-1a peptide, and extended with a biotinylated linker peptide, were
incubated with STEINLIN cells at 5 μM and 10 μM peptide in the presence of
2.5 μM AdEtOH. The efficiency of binding to APCs was assessed by flow
cytometry with streptavidin-conjugated R-PE. Binding was measured as percent
specific binding (L33 peptide defined as 100%). Each peptide that bound
efficiently to STEINLIN was also examined for binding to MHC-matched cell
lines DUCAF, EMJ, and EK such that binding to any other MHC class II
molecule on STEINLIN could be ruled out. Data points from independent
experiments are presented as dots, with bars representing mean ± SEM of at
least 3 experiments. Raw data values were median R-PE fluorescence intensity
on B-LCLs (gated by light scatter cytogram). Background intensity (cells
only, no peptide) was subtracted before calculating the specific binding
within each experiment. AdEtOH, adamantane ethanol; APC, antigen-presenting
cell; R-PE, R-phycoerythrin; B-LCL, B-lymphoblastoid cell lines