**8. Immune capture of T cell-derived sEV from plasma**

The T cell receptor (TCR) is expressed only on T lymphocytes, and an Ab specific for CD3, a protein component of the TCR complex, decorates the surface of sEV produced exclusively by T cells. A high-affinity Ab specific for CD3 proved to be an excellent candidate for immunocapture and subsequent characterization of sEV in plasma of patients with cancer or HDs [32]. T cell-derived sEV account for a considerable proportion of total plasma exosomes in cancer patients, and their phenotypic profiles examined by on-bead flow cytometry recapitulate those expressed by various T cell subsets as we reported [32]. CD3-based immune capture allowed for isolation from plasma of CD3(−) sEV fraction enriched in TEX and CD3(+) sEV fraction that was useful for evaluations of phenotypic and functional changes induced in the cancerreprogrammed T cells [33]. Thus, this type of immune capture allowed for simultaneous analysis of molecular profiles in tumor-derived and immune cell-derived sEVs in the same plasma sample. The procedure for immune capture of CD3+ EVs from the plasma of cancer patients is described in Current Protocols in Immunology [34].
