Hemopoietic progenitor cells are not directly stimulated by CD44 variant–specific antibodies.

CD44 v4- and/or v6-positive or negative bone marrow cells were examined for the presence of hematopoietic progenitor cells. (A) Bone marrow cells were sorted with CD44 variant–specific antibodies by MACS, and the sorted cells were cultivated in semisolid methylcellulose cultures with lineage-specific cytokines. GM-CSF was used to assay for granulocyte-macrophage progenitors (CFU-GM); IL-7 was used to assay for B-cell progenitors (CFU-B); and IL-3 + Epo was added to determine early erythroid progenitors (erythroid burst-forming units; BFU-e). Data shown are means (± SD) of the colony numbers obtained with 4 different wells, representing 1 of 5 independent experiments, when cells were separated by panning or FACS. (B) Bone marrow cells were sorted by MACS. The sorted cells were injected into 10 lethally irradiated mice at a concentration of 10⁴ cells per mouse. After 8 days, the numbers of colonies formed on spleens (CFUs-8) were counted and expressed as means ± SD. Similar results were obtained with cells separated by panning or FACS. (C) Bone marrow cells were used unsorted or sorted with CD44 variant–specific antibodies by MACS. The CD44 variant–positive and –negative cell populations were injected into 10 lethally irradiated mice. The control group with antibody represents mice reconstituted with unseparated bone marrow cells together with anti-CD44 v4 and v6 monoclonal antibodies. The data are the result of one experiment. A second independent experiment gave similar results. (D) Nonadherent cells from intact myeloid LTBMCs were harvested and cultured in methylcellulose as described in Figure 1B and D, except that CD44 variant antibodies (10 μg/mL) were added as indicated.