Peptide counts of MHC II–bound peptides in ADAMTS13-treated and PBS-treated DCs. Cells were treated with either 100 nM ADAMTS13 or PBS. All samples were immunoprecipitated using anti–MHC II antibody L243. Eluted peptides were analyzed by mass spectrometry and identified using Proteome Discoverer version 1.2. (A-B) Total amount of peptides (A) or ADAMTS13-derived peptides (B) was calculated in both samples. Peptides that did not fulfill our requirements based on rank and charge cross-correlation were excluded.