IGHE and neoplasm: Sequence similarity between the human and mouse CSPG4 antigen amino acid sequences is 83.55% (Supplementary Fig. 3), however CSPG4 IgE did not bind to mouse CSPG4-expressing tumor-derived mouse melanoma cell lines (Supplementary Fig. 4, mouse CSPG4 expression confirmed with an anti-mouse CSPG4 antibody by flow cytometric and Western Blot evaluations).