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J M Hows

Publications and source records attributed to J M Hows.

At least 55 records · Page 3Linked to original sources
PubMed1992

HLA-identical sibling donor bone marrow transplantation for chronic myeloid leukaemia in first chronic phase: influence of GVHD prophylaxis on outcome.

We have analysed the results of treating 140 consecutive patients with chronic myeloid leukaemia (CML) in chronic phase by bone marrow transplantation (BMT) using marrow from HLA-identical siblings performed between February 1981 and July 1991. Three different regimens were used sequentially to prevent graft-versus-host disease (GVHD): cyclosporin A (CsA) alone (n = 39), T-cell depletion of donor marrow (n = 51) and CsA with methotrexate (MTX) (n = 50). Eighty-four patients (61%) survive at a median of 49 months from BMT (range 3-120). The actuarial overall and leukaemia-free survivals at 5 years were 52% and 41% respectively. The actuarial probabilities of leukaemia-free survival and haematological relapse at 2 years for the CsA only group were 65% and 4%, for the T-cell depletion group 40% and 41% and for the CsA/MTX group 68% and 6% respectively. For the T-cell depletion group the probability of leukaemia-free survival was significantly lower (P less than 0.001) and the probability of relapse significantly higher (P less than 0.001) than for other methods of GVHD prophylaxis; differences between the other two groups were not significant. Previous reports that T-cell depletion with Campath-1M results in a high rate of relapse are confirmed. Patients in the CsA/MTX group have been monitored with cytogenetic and polymerase chain reaction studies for residual BCR/ABL transcripts. We conclude that the combination of CsA/MTX is currently the best available approach to prevention of GVHD after BMT for CML and in our hands it is not associated with a major risk of relapse.

Adolescent↗
PubMed1992

Current status of unrelated-donor bone marrow transplantation. The International Marrow Unrelated Search and Transplant (IMUST) Study.

1. The International Marrow Unrelated Search and Transplant (IMUST) Study 1 provides novel prognostic data on outcome of unrelated-donor (UD) searches for patients with well-defined clinical characteristics. Case-types analyzed by multifactorial methods reveal the importance of HLA phenotype, ethnic mismatching, and stage of disease at search request, in predicting search outcome. White patients, with common HLA types and early disease, were least likely to suffer search failure. In contrast, searches for non-White patients with unusual HLA phenotypes and advanced disease were most likely to fail. Of importance, 70% of patients had HLA phenotypes defined as uncommon. 2. Overall donor yield at the 2 UK registries between 1989 and 1991 was 7%, significantly below expectations. Reasons for this shortfall are that theoretical predictions did not consider ethnic mismatch and logistical delays incurred by outdated UD search routines and most importantly HLA-typing inaccuracies. 3. IMUST Study 2 is a prospective multicenter-controlled cohort study comparing HLA-identical sibling donor (ID) and UD-bone marrow transplantation (BMT) for factors affecting BMT outcome. Generous support was provided by 83 BMT centers worldwide. An interim analysis of 165 UD- and 368 ID-BMT, with at least 6 months follow-up after BMT, is described. Unifactorial analysis showed a probability of engraftment at day 100 of 89% after UD- compared with 98% after ID-BMT (p < 0.001). Probability of Grades II-IV acute graft-versus-host disease (AGvHD) at 100 days was 52% after UD- compared with 42% after ID-BMT (p < 0.01). Probability of overall survival at day 400 was 42% after UD- compared with 63% after ID-BMT (p < 0.001). Survival on day 400 of those patients receiving UD-BMT for early disease was encouraging at 52%. 4. Multifactorial analysis was performed on combined data from UD- and ID-BMT cohorts to identify various factors predicting engraftment, AGvHD, and overall survival. Survival after UD-BMT was increased by center experience of UD-BMT and the use of additional pretransplant immunosuppression. Survival was decreased in UD- compared with ID-BMT, by female donor to male recipient and poor-risk disease. Engraftment was improved in ID- compared with UD-BMT, and after UD-BMT at centers experienced in UD-BMT. Engraftment worsened with the use of ex-vivo T-cell depletion for GvHD prophylaxis, in chronic myeloid leukemia, and in male recipients of female marrow.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1992

Human cord blood: a source of transplantable stem cells?

In a preliminary study we have shown that optimally collected human umbilical cord (HUC) blood cells grow significantly better in long term cultures (LTC) than normal adult marrow cells (NBM) p = 0.0007. The LTC findings are supported by the observation in clonogenic assay that a similar number of GM-CFC colonies can be grown from HUC blood and NBM mononuclear cells (MNC). Also there is a trend towards a higher proportion of primitive erythroid (BFU-E) and primitive megakaryocyte colonies (MK-CFC containing greater than 20 cells) in HUC blood compared with NBM. We suggest that further work on the feasibility of a HLA typed, cryopreserved HUC blood bank as a source of unrelated haemopoietic 'stem' cells for clinical transplantation is indicated.

Blood Cell Count↗
PubMed1992

HLA-DR and DQ matching by DNA restriction fragment length polymorphism methods and the outcome of mixed lymphocyte reaction tests in unrelated bone marrow donor searches. The IMUST Study.

The use of DNA restriction fragment length polymorphism (DNA-RFLP) typing for HLA-DR and DQ genes was assessed in 96 patients who were HLA-A,B and DR matched by serology with one or more potential unrelated marrow donors (UD). Two hundred recipient-donor pairs from 10 transplant centres in the UK were studied. DNA-RFLP revealed serological errors in HLA-DR typing and identified additional recipient-donor mismatches. Of the 200 allegedly serologically matched pairs, 55 (28%) were mismatched for HLA-DR and/or DQ by DNA-RFLP typing. Of the 200 pairs, 68 (34%) mixed lymphocyte reactions (MLR) were negative and 132 (66%) positive. There was a significant correlation between DNA-RFLP defined mismatch and MLR positivity. However quantitative studies revealed no trend towards increasing MLR relative response index (RRI) with cumulative RFLP defined mismatch (i.e. for DR plus DQ compared with DR or DQ alone). RFLP matching for HLA-DR and DQ failed to predict a negative MLR. The RRI in the graft-versus-host direction was greater in RFLP matched pairs who carried HLA-DR4 than in matched pairs lacking DR4, suggesting that failure of RFLP to characterize DR4 subtypes was one reason why routine prediction of a negative MLR was not possible. Despite these limitations we have shown that DNA-RFLP is a reliable method for HLA-DR, DQ typing in routine UD searches in diverse clinical centres. By reducing the number of UD tested in MLR, RFLP typing can substantially reduce the work involved in donor selection.

Bone Marrow Transplantation↗
PubMed1991

Bone marrow transplantation: effects of conditioning and cyclosporin prophylaxis on microvascular permeability to a small solute (technetium 99m diethylene triamine penta-acetic acid).

Microvascular permeability to small diffusible solutes has rarely been measured at a clinical level. We have developed a simple non-invasive technique for measuring the permeability surface area (PS) product, which is suitable for clinical use. We illustrate its potential value in six subjects who underwent bone marrow transplantation for chronic myeloid leukaemia. These patients received high-dose cyclosporin A (CyA) for prevention of graft versus host disease (GVHD) and sustained an easily measurable increase in microvascular permeability to technetium 99m diethyltriamine penta-acetic acid (99mTc-DTPA). This was measured as the PS product, which increased from 1.1 (SD 0.3) to 2.2 (0.4) ml/min per 100 ml tissue between baseline and treatment with CyA for prevention of GVHD (P less than 0.01). The increase broadly correlated with nephrotoxicity which was measured, from the plasma DTPA clearance, as global glomerular filtration rate (GFR). This decreased from 106 (11.1) to 49 (6.7) ml/min (P less than 0.001). These abnormalities, both in PS product and GFR, were sustained for several months, after which they tended to return towards baseline levels. We conclude firstly that this technique has a potential clinical role and secondly that endothelial abnormalities due to CyA deserve further study.

Adult↗
PubMed1991

Mechanisms of graft failure after human marrow transplantation: a review.

Graft failure (GF) following bone marrow transplantation (BMT) in man is usually attributed to allograft rejection; however, other mechanisms of GF exist. Exposure of the developing allograft to viruses, myelotoxic drugs, and damage to the host-derived marrow stroma during graft-versus-host disease (GVHD) may all cause GF. Later, in the posttransplant course, recurrence of the original disease may ultimately destroy or replace the graft. Overall allogeneic rejection remains the most important cause of GF and most in vivo and in vitro evidence points to a T cell mechanism. The incidence of rejection after clinical BMT is very variable and highly dependent on HLA and non HLA histocompatibility differences between donor and recipient, the level of recipient sensitisation pre-BMT and the immunosuppressive protocols used pre-transplant and for the prevention of GVHD.

Bone Marrow Transplantation↗
PubMed1991

In vitro assessment of marrow 'stem cell' and stromal cell function in aplastic anaemia.

An in vitro model system is described that allows separate assessment of 'stem cell' and stromal cell function in aplastic anaemia (AA). Seven patients with non-severe AA, who had responded to immunosuppressive therapy and had haematological evidence of residual marrow function, were studied. Of these, three with otherwise typical AA had an acquired clonal cytogenetic marker. Purified bone marrow haemopoietic progenitors labelled with CD34 monoclonal antibody were positively selected using the fluorescence activated cell sorter (FACS) from both normal subjects and from patients with AA. The generative capacity of the CD34 positive cells was assessed by monitoring the output of granulocyte/macrophage colony forming cells (CFU-GM) in the non-adherent layer after inoculation onto irradiated performed long-term marrow culture (LTBMC) stromas. Stromal function in AA was assessed by inoculating CD34 positive cells from normal bone marrow onto performed irradiated stromas from patients with AA. Haemopoietic cell ('stem cell') function in AA was assessed by inoculating CD34 positive cells from AA patients onto confluent irradiated normal marrow stromas. Using these crossover/LTBMC experiments, all patients exhibited severe defects in haemopoietic cell function with normal functioning stroma. The proportion of CD34 positive cells present in bone marrow from these patients was reduced compared with controls, they comprised fewer small primitive 'blast-like' cells which in normal bone marrow are known to possess marrow repopulating ability, and demonstrated reduced clonogenic potential in short-term colony assays.

Adult↗
PubMed1991

Late onset immune pancytopenia following bone marrow transplantation.

A 17-year-old boy developed autoimmune pancytopenia in the absence of chronic graft-versus-host disease 170 d after allogeneic bone marrow transplantation (BMT) from his HLA identical brother. The anaemia and thrombocytopenia responded to conventional immunosuppressive treatment, but the neutropenia was refractory to this and to splenectomy and subsequent removal of splenic remnant. Following total lymphoid irradiation the neutrophil count rose to low normal levels but thrombocytopenia and anaemia secondary to marrow hypoplasia required transfusion support. Bone marrow function was finally normalized by an additional transfusion of donor marrow without prior immunosuppressive therapy. We conclude that late onset immune pancytopenia post BMT caused by antibodies of probable donor origin may be life threatening in the absence of chronic graft-versus-host disease.

Adolescent↗
PubMed1991

Origin and function of adherent lymphokine activated killer cells in patients with chronic myeloid leukaemia who relapse following bone marrow transplantation.

Adherent lymphokine activated killer (ALAK) cells are a subpopulation of activated natural killer (NK) cells with MHC unrestricted antitumour activity distinguished by their propensity to adhere to plastic in the presence of interleukin-2 (IL-2). We generated ALAK cells from seven patients with chronic myeloid leukaemia (CML) following Campath-1-depleted bone marrow transplantation (BMT). Five had relapsed and were in chronic phase, one had cytogenetic evidence of relapse and one had prior evidence of cytogenetic relapse but was in complete remission at time of study. Phenotypically the ALAK cells included both CD56+/CD3- NK cells and CD56-/CD3+ T cells. The CD3- subpopulation were studied cytogenetically and their functional activity tested in a 4 h 51Cr release cytotoxicity assay using the pretransplant leukaemia cells as targets. Cytogenetic studies showed that the ALAK cells from six patients were Ph negative, and where donor and recipient were sex mismatched, ALAK cells were exclusively of donor origin. In one patient ALAK cells were Ph positive and of recipient origin in eight of nine metaphases. In the 51Cr release assay the ALAK cells showed significant lysis of the pretransplant leukaemia in five of the seven patients tested. These data indicate that in CML patients who relapse post-BMT the NK cells are usually of donor origin but may be recipient-derived. In most patients these ALAK cells have antileukaemic activity in vitro.

Antigens, Neoplasm↗
PubMed1991

Cytotoxic T lymphocyte precursor (CTL-p) frequency analysis in unrelated donor bone marrow transplantation: two case studies.

HLA 'matched' unrelated donor bone marrow transplantation (BMT) is associated with an increased incidence and severity of acute graft-versus-host disease (GVHD) in comparison with HLA-identical sibling transplants. Using a limiting dilution analysis system for quantitating frequencies of alloreactive cytotoxic T lymphocyte precursors (CTL-p), we previously demonstrated a correlation between CTL-p frequency and HLA disparity between responder and stimulator, and between CTL-p frequency and the incidence of acute GVHD following HLA A, B, DR matched unrelated donor BMT. In this study we assayed CTL-p frequencies in two HLA 'matched' unrelated donor/patient pairs, with single HLA antigenic mismatches detected by allogenotyping or isoelectric focusing but not by HLA serology, and demonstrated that the CTL-ps were specifically directed at the mismatched antigen. Both class I and class II antigens were detected. These data, and our previous work, suggest that high CTL-p frequencies in HLA 'matched' unrelated pairs are indicative of HLA antigenic variants undetected by serology but recognized by molecular typing, and that these are responsible for the value of the assay in predicting acute GVHD after BMT. We propose that this assay system be used in aiding final donor selection before unrelated or mismatched related donor BMT.

Bone Marrow↗