MRC1 and cancer: Consistent with previous work concerning cancer cell-targeting BiTEs [32], FRβ and CD206 BiTE-induced T cell-mediated killing of macrophages was dependent on perforin and not death receptor pathways, with a significant decline in BiTE-mediated MDM cytotoxicity upon addition of a perforin inhibitor, concanamycin A, but not inhibitors of Fas/FasL or TRAIL (Additional file 4).