Human T cells are effectively targeted in vivo and in vitro. (A) Flow plots showing levels of human T cells in the PB of UCB-CD34⁺ humanized NSGS mice before and 3 days after injection of control (CNTL), ATG, or OKT3 antibodies. Three separate mice are shown for each group. SSC, side scatter. (B) The spleens of each of the mice from A were analyzed 7 days after antibody injection. Both CD45⁺CD3⁺ T cells and CD45⁺CD3⁻ non-T cells are gated. (C) Antibody-labeled UCB was co-cultured for 4 days on OP9-DL1 stroma to promote T-cell expansion with or without peritoneal macrophages from NSG mice. IVIG, intravenous immunoglobulin. (D) The decrease in T cells in the presence of macrophages relative to the same antibody labeled culture without macrophages is shown. *P < .05. (E) Representative flow plots after 4 days of coculture to highlight OKT3 blockage of CD3 and the decreased CD8⁺ T-cell percentages after macrophage exposure.