PECAM1 and B-cell chronic lymphocytic leukemia: Regarding protein content, Belov et al. [29] showed that CD19+ EVs from the plasma of CLL patients express a subset (~40%) of proteins detected on CLL cells from the same patients: moderate or high levels of CD5, CD19, CD31, CD44, CD55, CD62L, CD82, HLA-A, B, C, HLA-DR; low levels of CD21, CD49c, CD63.