CD53 and melanoma: We developed and optimized a cell-based ELISA for specific detection oftumor-reactive antibodies in order to obtain a robust and optimized system forthe detection of anti-tumor antibodies from patients (Figure S1).We first evaluated the sensitivity and specificity of an IgG antibody against amelanoma cell surface antigen (HMW-MAA), expressed on A-375 melanoma cells usingimmunocytochemistry (cytospins) and live cell flow cytometry.