[23] Phenotypic characterisation confirmed that CLL cell-derived exosomes carry classical exosomal markers such as MHC class I and II molecules, CD81, and TSG-101, as well as elements unique to CLL cells such as IgM, CD19, Lyn, and the integrin ITGA4 in a specific instance. Here, CD81 is linked to B-cell chronic lymphocytic leukemia.