CD81 and brain neoplasm: The characteristics of the extracellular vesicles derived from a patient with brain tumor were determined by measuring the size by dynamic light scattering using the Zeta sizer (Figure 4C), the binding affinity (Figure 4D) of Hsp70 carrying exosomes to cmHsp70.1 mAb, and typical exosomal surface markers (Figure 4E) such as the tetraspanins CD9, CD81, and mHsp70 by flow cytometry.