Analysis of MHC II ligands identified in ADAMTS13-treated mDCs. ADAMTS13-treated cells isolated from donor 15 were immunoprecipitated using either an anti–MHC II antibody or an isotype control antibody. Eluted peptides were analyzed by mass spectrometry and identified by Proteome Discoverer version 1.2. The total number of ADAMTS13-derived peptides was determined by counting the specific peptides that met our exclusion criteria.