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We tested conditioned media from 12 patients with T lymphocyte neoplasms and four T cell lines for their ability to stimulate the in vitro growth of erythroid-burst-forming units (BFU-E) from bone marrow mononuclear cells in a methylcellulose culture system. Nine patients suffered from acute lymphocytic leukemia, two from chronic lymphocytic leukemia, and one from non-Hodgkin's lymphoma. The T lymphocytes were characterized by a series of monoclonal antibodies and their stage of development was correlated with their ability to produce burst- promoting activity (BPA). Conditioned media from cells classified as prothymocytes (three cases), common thymocytes (one case), mature thymocytes (three cases), and mature lymphocytes of the helper subtype (two cases) increased BFU-E proliferation four- to 19-fold over control values using normal bone marrow as target cells. Conditioned media from OKT8+ malignant T lymphocytes (three cases) did not enhance BFU-E proliferation. Conditioned media from cells classified as immature T cells stimulated CFU-GM proliferation in only one of seven cases even though they secreted BPA. Conditioned media from three of the four cell lines stimulated by phytohemagglutinin, enhanced BFU-E growth. Our results indicate that malignant cells that have characteristics of immature T cells are able to produce BPA. Studies using techniques to isolate homogeneous populations of normal T cell subsets are required to determine whether normal immature T lymphocytes have the same capability.

Mitogen-stimulated murine spleen cells produce humoral substances capable of supporting murine hematopoiesis and pluripotent stem cell proliferation in vitro. Thus, we evaluated conditioned media generated by human spleen cells (SCM) in the presence or absence of mitogens for factors stimulatory for human pluripotent (CFU-GEMM), erythroid (BFU- E), and myeloid (CFU-GM) precursors. Two and one half percent to 10% SCM stimulated proliferation of all three types of precursor cells from nonadherent buoyant human marrow target cells. Mitogen-stimulated SCM augmented CFU-GM (175% to 225%), whereas CFU-GEMM and BFU-E growth was essentially unchanged. Cell separation procedures used to determine which cells provided these microenvironmental stimuli indicated that nonadherent mononuclear spleen cells provided the bulk of the CSF-GM, whereas adherent cells (95% nonspecific esterase + monocyte- macrophages) and nonadherent cells provided similar proportions of CSF- mix and erythroid burst-promoting activity (BPA). The nonadherent cells generating high levels of CSF-mix, BPA, and CSF-GM were predominantly Leu-1-negative, ie, non-T, cells. In the presence or absence of mitogens, SCM was a more potent source (1.3- to 3.8-fold) than peripheral leukocyte CM of the growth factors for the three progenitor cell types. Specific in situ cytochemical stains for analyzing morphology of myeloid colonies demonstrated that SCM stimulated the proliferation of the same types and proportions of colonies as human placental CM, suggesting that these CMs may contain similar CSF-GMs. These data show the contribution of spleen cell subsets to the generation of hematopoietic growth factors and the responsiveness of these cells to various mitogenic stimuli.

The phenomenon of marrow rejection following supralethal radiochemotherapy was explained in the past mainly by non-T-cell mechanisms known to be resistant to high-dose irradiation. In the present study a low but significant number of radiochemoresistant-clonable T cells was found in the peripheral blood and spleen of Rhesus monkeys following the cytoreductive protocol used for treatment of leukemia patients prior to bone marrow transplantation. More than 95% of the clonable cells are concentrated in the spleen 5 days after transplant. The cells possess immune memory as demonstrated by the generation of alloreactive-specific cytotoxicity. The present findings suggest that host-versus-graft activity may be mediated by alloreactive T cells. It is hoped that elimination of such cells prior to bone marrow transplantation will increase the engraftment rate of HLA-nonidentical marrow in leukemia patients.

The in vitro effect of ciprofloxacin and pefloxacin on growth of normal hematopoietic progenitor cells and on leukemic cell lines was investigated. Ciprofloxacin and pefloxacin caused dose-dependent inhibition of colony formation both from normal bone marrow cells and from the leukemic line K-562 cells. This inhibition exerted by ciprofloxacin and pefloxacin was statistically significant at concentrations of 25 micrograms/ml and above. Ciprofloxacin appeared to be the most potent inhibitor of colony formation among the antimicrobial agents tested. Although the inhibitory effect of pefloxacin on normal hematopoietic stem cells was similar to that of cefazolin and chloramphenicol, the inhibitory effect of pefloxacin on leukemic cells was more prominent than that of cefazolin and chloramphenicol. In a proliferation assay in liquid culture of the cell line HL-60, ciprofloxacin and pefloxacin caused a dose-dependent inhibition of cell proliferation. Both drugs failed to induce cellular differentiation, as assessed by the nitrogen blue tetrazolium dye reduction assay. In therapeutic concentrations no cumulative toxic effect of the combination of ciprofloxacin with cytosine-arabinoside, vincristine, actinomycin D and doxorubicin on colony formation by HL-60 cells was observed. It is concluded that ciprofloxacin does not exert in vitro inhibitory effect on human leukemic cells when assayed at concentrations of less than or equal to 5 micrograms/ml. However, at concentrations of 25 and 50 micrograms/ml of ciprofloxacin alone and in combination with several antineoplastic agents exerts an inhibitory effect on colony formation.

ABSTRACTMobilized human peripheral blood progenitor cells are potential alternatives to bone marrow cells as targets for ex vivogene transfer. We report the transduction efficiency of retroviral-mediated gene transfer into myeloid progenitors of peripheral blood progenitor cell (PBPC) harvests, mobilized by high-dose cyclophosphamide and GM-CSF, compared with nonmobilized bone marrow (BM). Eleven PBPC samples were enriched for CD34cells, preincubated with IL-3 (10 ng/ml), IL-6 (50 ng/ml), and 10% autologous plasma for 42 hr, and transduced over a 6-hr incubation with IL-3 IL-6 and a retroviral vector carrying the NeoRgene. NeoR-specific sequences were detected by polymerase chain reaction in 10 cell pellets (91%). Gene expression in CFU-GM colonies was found in nine transduced samples (82%), with a mean transduction efficiency of 5.2% (95% CI, 1.311.8%) CFU-GM per PBPC sample. In univariate analysis, a higher transduction efficiency into CFU-GM correlated significantly with a higher CFU-GM concentration in the CD34-enriched sample (p0.009), a shorter interval from diagnosis (p< 0.001), and fewer months of prior cytotoxic treatment (p0.001); correlation with younger age was of borderline statistical significance (p0.077). In multivariate analysis a shorter interval from diagnosis and, to a lesser degree, a higher CFU-GM concentration in the CD34-enriched sample were independent predictors of higher transduction efficiency. Twelve BM samples were similarly transduced; 11 pellets were PCR positive. CFU-GM NeoRgene expression was 4.2% (95% CI, 2.07.2%) CFU-GM per BM sample, which was not significantly different from the transduction efficiency into PBPC cells. No correlation was found between the transduction efficiency of CFU-GM in BM samples and CFU-GM concentration in the CD34-enriched sample, time from diagnosis, months of prior cytotoxic treatment, and/or patient age. Our data suggest that the transduction efficiency ex vivomay be influenced by time from diagnosis, CFU-GM concentration in the sample, and possibly by the extent of prior cytotoxic administration.

A neutropenic patient with acute myeloid leukemia developed nasal and perinasal infection caused by the fungus Exserohilum rostratum. Early amphotericin B treatment along with marrow recovery resulted in resolution of the infection. A review of other previously reported cases of Exserohilumand Bipolarisinfections show a favourable outcome in most patients who receive systemic antifungal treatment with amphotericin B.