Influence of T-lymphocytes and lactoferrin on the survival-promoting effects of IL-1 and IL-6 on human bone marrow granulocyte-macrophage and erythroid progenitor cells.

Purified recombinant human (rhu) interleukin (IL)-1 alpha, rhuIL-6, iron saturated lactoferrin (LF), and T-lymphocytes were assessed for their effects on the survival of granulocyte-macrophage (granulocyte-macrophage colony-forming units, CFU-GM) and erythroid (erythroid burst-forming units, BFU-E) progenitor cells from human low-density (LD) and nonadherent LD T-lymphocyte-depleted (NALT-) bone marrow (BM) cells. Colony-stimulating factor (CSF) deprivation studies showed that 10 ng/ml IL-1 alpha could promote the survival of CFU-GM and BFU-E from NALT- BM cells. Concentrations of 1 ng/ml IL-1 alpha and 1-100 ng/ml IL-6 alone could not promote progenitor cell survival from NALT- BM cells; however, concentrations of 1 ng/ml each of IL-1 alpha and IL-6 could synergize to promote the survival of CFU-GM but not of BFU-E. The combination of these low concentrations of IL-1 alpha and IL-6 could, however, support the survival of BFU-E in the presence of purified T-lymphocytes. LF could decrease the survival of CFU-GM and BFU-E from LD but not from NALT- BM cells, apparently due to the inhibition of IL-1 release from monocytes in this cell population. The suppressive effect of LF on the survival of those progenitor cells was abolished by concentrations of 10 ng/ml IL-1 alpha or 1 ng/ml each of IL-1 alpha and IL-6. These results demonstrate that the survival of human marrow CFU-GM and BFU-E can be influenced by IL-1, IL-6, LF, and T-lymphocytes.