Homing of enriched human CD34⁺ progenitor cells in NOD/SCID mice that underwent transplantation is blocked by anti-CD44 mAbs, hyaluronic acid (HA), and hyaluronidase (Hase) treatment. Enriched human MPB CD34⁺ cells, either untreated (ctrl) or after blocking with antihuman CD44 mAbs (clones BU52 and F10-44-2, as indicated) or following treatment with 0.5 μM of either HA or chondroitin sulfate (CS), were injected intravenously into the NOD/SCID mice (5 × 10⁵ cells per mouse, 24 hours after sublethal irradiation). Another group of recipients was also injected intravenously with the degrading enzyme, Hase, immediately prior to cell transplantation. BM and spleen of recipient mice were analyzed for the presence of human cells using human-specific anti-CD34–FITC and CD38-PE mAbs. Results show the percentage of human CD34⁺ cells that homed to the BM (A) and spleen (B) relative to control. (mean ± SD from 3 independent experiments, 3 to 4 mice per treatment in each experiment, ^*P < .05). Data from a representative experiment showing the number of human cells per 10⁶ acquired cells in the BM (C) and spleen (D) of recipients. Homing of enriched CB CD34⁺ cells untreated (ctrl) or treated either with anti-CD44 mAbs or with the isotype control to the BM (E) and spleen (F) of the recipients (mean ± SD from 3 independent experiments, 3 mice per treatment, ^*P < .05).