Host CD8⁺ T cells reactive with cord blood alloantigens are present in 9 patients rejecting double CBT. Day 26 posttransplantation PBMCs were stimulated against LCLs generated from the transplanted cord units. (A) The majority of CD3⁺ cells are CD8⁺. (B) The CD8⁺ cells express primarily effector/effector memory phenotype (CD45RO^+/−CCR7⁻). (C) Host CD8⁺CD45RO^+/−CCR7⁻ cells stain positive for intracellular IFN-γ staining after stimulation with each of the transplanted cord unit.