CD8A and neoplasm: In addition, exosomes derived from domesticated bone marrow cells can also suppress immunity and thus promote metastasis, e.g. exosomes from tumor-bearing mouse bone marrow-derived cells (BMDC) carry PD-L1, and PD-L1 on these exosomes is biologically functional and can inhibit CD8 T cell proliferation and activation in vitro and in vivo (34).