Ex vivo expansion of peripheral blood progenitor cells with recombinant cytokines.

Peripheral blood mononuclear cells were isolated and cultured in the presence of Steel factor and/or PIXY321, a GM-CSF/IL-3 fusion protein. We compared the number of colony forming cells (CFC) per culture on day zero to the number of CFC after liquid culture in the presence of these cytokines. After a four day incubation with PIXY321 and Steel factor the number of CFU-GM increased 5.6-fold and the number of BFU-E increased 2.2-fold in four separate experiments. The expansion on day 8 post incubation was 16.1-fold for myeloid colony formation and 9.7-fold for erythroid colony formation. These studies demonstrate the potential to expand CFC from peripheral blood with a simple ex vivo culture procedure.

The effects of interleukin 7 (IL-7) on human bone marrow in vitro.

Interleukin 7 (IL-7) stimulates the proliferation of pre-B cells from long-term murine lymphoid cultures and normal bone marrow. In addition, IL-7 stimulates the proliferation of murine T cells, including fetal and adult thymocytes as well as peripheral T cells. Flow cytometry and cell enumeration analyses were carried out on light-density human bone marrow cells incubated in the presence or absence of IL-7. The data showed no evidence for a proliferative effect of IL-7 on B-lineage cells expressing CD24 or on myeloid cells expressing CD15; however, IL-7 did stimulate the growth of T cells expressing CD3. After 16 days of stimulation the number of CD3+ cells in marrow cultures increased 350% in the presence of IL-7. In contrast, cultures incubated in the absence of IL-7 showed a 50% decrease in the number of T cells, with a preponderance of myeloid lineage cells. Flow cytometry indicated that cells from IL-7-stimulated cultures were mature T cells because they also expressed cell surface antigens for either CD4 or CD8. These studies show that in contrast to the murine system, IL-7 does not appear to stimulate the growth of human pre-B cells from adult human bone marrow. This is consistent with other experiments that suggest that human pro-B cells and not human pre-B cells respond to IL-7. It appears that IL-7 preferentially promotes the growth of T cells from human marrow.