Reactivity of patient plasma with DBY peptides. Plasma samples from 27 male patients with female donors were found to have developed antibodies to DBY peptides after allogeneic HSCT. The left axis (red bars) plots the frequency of recognition for each DBY peptide as a percentage of the 27 DBY peptide–positive samples. The right axis (blue bars) indicates the number of disparate amino acids comparing DBY and DBX for each peptide.