CTLA4 and melanoma: In the blood of non-progressing patients with different forms of metastatic cancers (melanoma, lung adenocarcinoma, non-small cell lung carcinoma and renal cell carcinoma) treated with immune checkpoint blockade immunotherapy (anti-CTLA4, anti-PD-1) or by chemotherapy, an active humoral immune response could be detected, characterized by somatic hypermutation, IgG class switch and clonal expansion of plasmablast (CD20− CD19+ CD38hi CD27+ CD3− CD14− IgA− IgM−).