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Five patients with adult-onset metachromatic leukodystrophy (MLD) underwent allo-SCT. Conditioning was reduced in intensity and grafts were obtained from voluntary unrelated donors. All but one graft were depleted of T-lymphocytes. Patient age at transplantation varied from 18 to 29 (median, 27) years. Two patients rejected their graft and MLD progressed. The recipient of the unmanipulated graft converted to complete donor chimerism with normalization of arylsulphatase A (ARSA) levels. Despite ARSA normalization, he deteriorated. Another patient was a mixed chimera. Following escalated doses of donor lymphocyte infusions he converted to complete donor chimerism. His levels of ARSA correlated positively with the percentage of donor cells and MLD was not progressive. The fifth patient died after 35 days from complications associated with GVHD. We conclude that results of allo-SCT in symptomatic MLD patients are poor. However, allo-SCT may stop progression of MLD in selected patients. [ABSTRACT FROM AUTHOR]

Background Immunomagnetic selection of CD34+ hematopoietic progenitor cells (HPC) using CliniMACS CD34 selection technology is widely used to provide high-purity HPC grafts. However, the number of nucleated cells and CD34+ cells recommended by the manufacturer for processing in a single procedure or with 1 vial of CD34 reagent is limited. Methods In this retrospective evaluation of 643 CliniMACS CD34-selection procedures, we validated the capacity of CliniMACS tubing sets and CD34 reagent. Endpoints of this study were the recovery and purity of CD34+ cells, T-cell depletion efficiency and recovery of colony-forming units-granulocyte-macrophage (CFU-GM). Results Overloading normal or large-scale tubing sets with excess numbers of total nucleated cells, without exceeding the maximum number of CD34+ cells, had no significant effect on the recovery and purity of CD34+ cells. In contrast, overloading normal or large-scale tubing sets with excess numbers of CD34+ cells resulted in a significantly lower recovery of CD34+ cells. Furthermore, the separation capacity of 1 vial of CD34 reagent could be increased safely from 600×106 CD34+ cells to 1000×106 CD34+ cells with similar recovery of CD34+ cells. Finally, T-cell depletion efficiency and the fraction of CD34+ cells that formed CFU-GM colonies were not affected by out-of-specification procedures. Discussion Our validated increase of the capacity of CliniMACS tubing sets and CD34 reagent will reduce the number of selection procedures and thereby processing time for large HPC products. In addition, it results in a significant cost reduction for these procedures. [ABSTRACT FROM AUTHOR]

Using red cell phenotyping (RCP) and/or cytogenetics (CYT) we identified 19 patients with persisting mixed chimerism (MC) among 231 patients transplanted with partially T cell-depleted stem cell grafts from HLA-identical siblings. Persisting MC is defined as MC for more than 2 years in patients without any evidence of relapse. Median leukemia-free survival in these patients was 150 (range, 50-218) months. Diagnoses were ALL (n = 10); AML (n = 2); CML (n = 2); NHL (n = 2); MDS (n = 1); MM (n = 1) and SAA (n = 1). Purpose of this study was the longterm follow-up of MC and definition of patterns of chimerism in the various subsets of PBMCs and granulocytes. Using a PCRSTR technique CD3[sup +]/CD4[sup +] (T4 lymphocytes), CD3[sup +]/CD8[sup +] (T8 lymphocytes), CD45[sup +]/CD19[sup +] (B lymphocytes), CD45[sup +]/CD14[sup +] (monocytes), CD45[sup +]/CD15[sup +] (granulocytes) and CD3[sup -]/CD56[sup +] (NKcells) were analyzed. The majority of patients with persisting MC were conditioned with a less intensive conditioning regimen and had little GVHD. Sequential monitoring of the chimerism resulted in a group of patients (n = 7) with very slow transient mixed chimerism that resulted in complete DC after median 7 years. Another nine patients had a relatively high percentage of persisting autologous cells for a median of 12 years and in three patients we observed a stable low percentage of autologous cells. Only two out of 19 patients (AML-CR1, CML-CP1) relapsed during follow-up. Both patients had a relatively high percentage of autologous cells. Chimerism in granulocytes and PBMC subsets was analyzed at a median of 8 years after SCT in nine patients. In five patients mixed chimerism simultaneously detected by RCP and CYT was associated with MC in all subsets. Within each individual patient the percentages of donor and recipient cells were very different between the different subsets. Two CML-CP1 patients were mixed chimera in only two subsets and in one patient these... [ABSTRACT FROM AUTHOR]

One hundred and thirty-one patients were transplanted for AML-CR1, ALL-CR1 or CML-CP1 after conditioning with 120 mg/kg body weight cyclophosphamide and 2 × 4.5 Gy TBI. Conditioning was intensified with the addition of 42 mg/m2 idarubicin. Grafts were T cell-depleted using counterflow centrifugation. Donors were HLA-identical siblings. We compared outcome of BMT in 109 patients aged less than 50 (median, 35) years with that of 22 patients with an age of 50 years or more (median, 53 years). For the patients aged <50 years, 2-year probabilities of treatment-related mortality, relapse, survival and leukemia-free survival were 26% (95% CI, 17% to 35%), 26% (95% CI, 17% to 35%), 64% (95% CI, 55% to 73%), and 56% (95% CI, 47% to 65%). For the patients aged 50 years, these figures were 13% (95% CI, 0% to 30%), 24% (95% CI, 6% to 42%), 66% (95% CI, 46% to 86%), and 67% (95% CI, 47% to 87%), respectively. outcome did not differ significantly between the two age groups. TRM was within the range of that reported in the literature for recipients of T cell-depleted grafts. We conclude that T cell-depleted transplantation after a conditioning regimen that was intensified with the addition of idarubicin is feasible in patients aged 50 years. For this age group of patients, results of nonmyeloablative regimens should be compared with that obtained with T cell-depleted grafts. Bone Marrow Transplantation (2000) 26, 17–22. [ABSTRACT FROM AUTHOR]

Using counterflow centrifugation elutriation (CCE) lymphocytes can be separated from CD34+ populations based on size. Immature progenitors tend to be smaller than mature cells suggesting that CCE introduces loss of stem cells. We compared the separation of 12 PBSC with 16 BM transplants. Cells were separated in 12 fractions (3000–2200 r.p.m.) and the rotor off (RO) fraction. Separation patterns of BM and PBSC were comparable. B cells were collected in the high speed fractions followed by T and NK cells. In contrast, progenitor cells were collected in lower speed fractions. By adding successively T cell-depleted fractions to the RO fraction a BM transplant could be composed containing 0.7 × 106 T cells/kg and 90%, 89% and 68% recovery of CD34+, CFU-GM and BFU-E. PBSC were separated in four CCE runs inducing higher numbers of T cells in the graft (4.4 × 106/kg) and 54% CD34+, 46% CFU-GM and 37% BFU-E recovery. Time of engraftment was not delayed and no graft failure was observed. The higher number of T cells was not associated with higher incidence of GVHD. Acute GVHD grade III occurred in 0 of 16 BM and two of 12 PBSC recipients; extensive chronic GVHD was observed in four of 15 and three of nine recipients, respectively. To study immature cells in the graft, CD34 subpopulations and cells with long-term repopulating ability, determined using cobble-stone area formation (CAFC assay), were evaluated in each fraction. The separation patterns in BM and PBSC were comparable. Cells with mature and immature phenotype were enriched in lower speed fractions (mean recovery of 74% CD34+/CD13-/DR-). The CAFC week 2, 4 and 6 were also enriched in these fractions. These data show that the used CCE procedure is a reliable method to deplete T cells from stem cell transplants without substantial loss of immature and mature progenitors. [ABSTRACT FROM AUTHOR]

We studied the outcome of BMT in 38 consecutive CML patients in CP1 who received transplants depleted of lymphocytes using counterflow centrifugation. In all patients the conditioning regimen was intensified by the addition of anthracyclines. Donors were HLA, MLC-identical siblings. Six patients (16%) died within 6 months. All 37 patients with a follow-up of more than 0.5 months engrafted and only one (3%) suffered from acute GVHD  grade 3. Chronic GVHD was evaluable in 33 patients and was extensive in six (18%). The projected 5-year probabilities of hematologic, cytogenetic and molecular relapse were 30% (95% confidence interval (CI), 10–49%), 35% (95% CI, 14–56%), and 34% (95% CI, 13–55%), respectively. The projected 5-year probability of survival was 68% (95% CI, 50–86%). Projected at 5 years, probablities of leukemia-free survival (LFS) in hematologic, cytogenetic and molecular remission were 55% (95% CI, 37–73%), 51% (95% CI, 32–69%), and 51% (95% CI, 32–70%), respectively. All patients with relapse but one who relapsed in blastic phase were treated with retransplantation (n= 1) or with the infusion of lymphocytes (n= 6). Six patients regained second hematologic remission and five entered second cytogenetic and molecular remission. Including these patients, the probability of survival in first or second hematologic remission at the end of follow-up was 68% (95% CI, 50–86%). The probabilities of survival in first or second cytogenetic and molecular remission at the end of follow-up were both 61% (95% CI, 42–80%). We advocate revaluation of T cell depletion of donor marrow for patients with CML-CP1, especially for those at high risk of developing GVHD. [ABSTRACT FROM AUTHOR]

Graft-versus-host disease (OVHD) after allogeneic bone marrow transplantation (BMT) is initialed by immunocompetent T cells present in the graft. Selective elimination of distinct T-cell subsets or a sufficient, but not complete T-cell depletion, might abolish severe GVHD without graft rejection and loss of the anti-tumour potential. In this study we analysed the efficacy of different monoclonal antibodies (MoAb) WT32 (CD3). OKT4 (CD4), T101 (CD5), WT1 (CD7), and WT82 (CD8) with respect to their cytotoxicity to T cells either as immunotoxin (IT) or in combination with complement. The cytotoxic potential was assessed by protein synthesis inhibition and clonogenic assays. The ricin A conjugated MoAb exerted only a minor effect on blood or bone marrow T cells, although they were highly inhibitory to T-cell lines. However, in the presence of 20 mM ammonium chloride. IT directed against CD3, CD5, and CD7 were highly cytotoxic. IT directed against CD4 and CDS were less effective, due to a low internalization. The complement-mediated cytotoxicity was efficient for all antigens used. The natural killer (NK) activity, as measured by cytotoxicity to K562, was hardly depressed by anti-CD3, anti-CD4, anti CD5, and anti-CD8, but was eliminated by anti-CD7. All procedures used had only a minimal effect on haematopoietic progenitors us measured by CFU-GM and BFU-E assays. We concluded that, although the T-cell population can be eliminated with the combination of anti-CD3, anti-CD5, and anti-CD7 antibodies plus complement, IT with 20 mM NH4Cl appear to kill higher amounts of T cells. Selective elimination of CD4- and CD5-positive cells is effectively obtained by MoAb with complement. [ABSTRACT FROM AUTHOR]

In the context of ex vivo T cell elimination from bone marrow, the anti-T cell cytotoxic potential of immunotoxins (IT) prepared by conjugation of the monoclonal antibodies (MoAb) WT32 (CD3). T101 (CD5), and WT1 (CD7) to ricin A chain was evaluated. The cytotoxicity of IT was based on protein synthesis inhibition in human T cell lines: CH1, CEM, HPB-ALL, and Jurkat, and appeared closely related to the antigen density and internalization rate of the IT. Normal unstimulated T cells appeared to be rather insensitive to IT not due to a low antigen density or decreased internalization. The cytotoxicity of IT to T cells could be enhanced considerably by NH4Cl. Treatment of T cells with a cocktail of IT (10-8 M) and 20 mM NH4Cl resulted in a 5000-fold cytoreduction as measured by clonogenic assays of limiting T cell dilutions, whereas the haematopoietic progenitor cells remained unaltered. Stimulation of T cells with phytohaemagglutinin (PHA) prior to incubation with IT considerably increased the sensitivity to IT treatment. Thus, normal I cells are less sensitive to anti-T cell IT than T cell lines and activated T cells. This suggests that a low protein synthesis is responsible for the resistance to IT. However, a high specific cytotoxicity of 11 to normal 1 cells can be achieved in the presence of 20 mM ammonium chloride. [ABSTRACT FROM AUTHOR]