The purpose of this study was to evaluate human umbilical cord blood as an alternative to bone marrow in the provision of transplantable stem/progenitor cells for hematopoietic reconstitution. Although no direct quantitative assay for human hematopoietic repopulating cells is at present available, the granulocyte-macrophage progenitor cell (CFU-GM) assay has been used with success as a valid indicator of engrafting capability. We examined greater than 100 collections of human umbilical cord blood for their content of nucleated cells and granulocyte-macrophage, erythroid (BFU-E), and multipotential (CFU-GEMM) progenitor cells, in many cases both before and after cryopreservation. First it was determined that granulocyte-macrophage, erythroid, and multipotential progenitor cells remained functionally viable in cord blood untreated except for addition of anticoagulant for at least 3 days at 4 degrees C or 25 degrees C (room temperature), though not at 37 degrees C, implying that these cells could be satisfactorily studied and used or cryopreserved for therapy after transport of cord blood by overnight air freight carriage from a remote obstetrical service. Granulocyte-macrophage progenitor cells from cord blood so received responded normally to stimulation by purified recombinant preparations of granulocyte-macrophage, granulocyte, and macrophage colony-stimulating factors and interleukin 3. The salient finding, based on analysis of 101 cord blood collections, is that the numbers of progenitor cells present in the low-density (less than 1.077 gm/ml) fraction after Ficoll/Hypaque separation typically fell within the range that has been reported for successful engraftment by bone marrow cells. Another observation of practical importance is that procedures to remove erythrocytes or granulocytes prior to freezing, and washing of thawed cells before plating, entailed large losses of progenitor cells, the yield of unwashed progenitor cells from unfractionated cord blood being many times greater. The provisional inference is that human umbilical cord blood from a single individual is typically a sufficient source of cells for autologous (syngeneic) and for major histocompatibility complex-matched allogeneic hematopoietic reconstitution.

Stromal cell-derived factor 1 (SDF1/ CXCL12) and its cognate receptor, CXCR4, play key regulatory roles in CD34 ؉ cell trafficking. We investigated whether AMD3100, a selective CXCR4 antagonist, could mobilize hematopoietic progenitor cells from marrow to peripheral blood in healthy human volunteers. Initially, 10 persons each received a single dose of AMD3100 (80 g/kg subcutaneously), which induced rapid, generalized leukocytosis associated with an increase in peripheral blood CD34 ؉ cells, representing pluripotent hematopoietic progenitors by in vitro colony-forming unit assays, from 3.8 ؎ 0.5/L to 20.7 ؎ 3.5/L at 6 hours. Subsequent dose-response studies showed a maximum increase in circulating CD34 ؉ cells from 2.6 ؎ 0.3/L to 40.4 ؎ 3.4/L at 9 hours after 240 g/kg AMD3100. Serial administration of AMD3100 (80 g/kg/d for 3 days) resulted in consistent, reversible increases in peripheral blood CD34 ؉ cells. AMD3100 was well tolerated and caused only mild, transient toxicity. These findings suggest potential clinical application of AMD3100 for CD34 ؉ cell mobilization and collection for hematopoietic stem cell transplantation.

CC chemokine receptor 1 (CCR1) is expressed in neutrophils, monocytes, lymphocytes, and eosinophils, and binds the leukocyte chemoattractant and hematopoiesis regulator macrophage inflammatory protein (MIP)-1α, as well as several related CC chemokines. Four other CCR subtypes are known; their leukocyte and chemokine specificities overlap with, but are not identical to, CCR1, suggesting that CCR1 has both redundant and specific biologic roles. To test this, we have developed CCR1-deficient mice (−/−) by targeted gene disruption. Although the distribution of mature leukocytes was normal, steady state and induced trafficking and proliferation of myeloid progenitor cells were disordered in −/− mice. Moreover, mature neutrophils from −/− mice failed to chemotax in vitro and failed to mobilize into peripheral blood in vivo in response to MIP-1α. Consistent with this, −/− mice had accelerated mortality when challenged with Aspergillus fumigatus, a fungus controlled principally by neutrophils. To test the role of CCR1 in granuloma formation, we injected Schistosoma mansoni eggs intravenously, and observed a 40% reduction in the size of lung granulomas in −/− mice compared to +/+ littermates. This was associated with increased interferon-γ and decreased interleukin-4 production in −/− versus +/+ lung lymph node cells stimulated with egg-specific antigen, suggesting that CCR1 influences the inflammatory response not only through direct effects on leukocyte chemotaxis, but also through effects on the type 1–type 2 cytokine balance. Thus CCR1 has nonredundant functions in hematopoiesis, host defense, and inflammation.