Biomedical subjects
A J Barrett
Publications and source records attributed to A J Barrett.
Cellular and cytokine-mediated effects of CD4-positive lymphocyte lines generated in vitro against chronic myelogenous leukemia.
Leukemia cells from a patient with chronic myelogenous leukemia (CML) in accelerated phase were used to generate CD4+, CD8- T lymphocyte lines from an unrelated normal subject sharing HLA-A2 and DR4 with the patient. In chromium release cytotoxicity assays, lines showed specificity for patient cells and were unreactive against third-party CML and K562 cells. Cytotoxicity was blocked by anti HLA-DR on target cells. Some lines showed preferential cytotoxicity to PHA-induced lymphoblasts and some to CML cells. There was a broad correlation between cytotoxicity to CML cells by 51Cr release and CFU-CM inhibition. However, even weakly cytotoxic lines were inhibitory to CML CFU-GM. This effect was partly mediated by the T cell line supernatant: four of five supernatants tested inhibited the growth of CFU-GM. Antibody neutralization studies demonstrated the presence of gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) in these supernatants. There was a greater suppression of CML CFU-GM when compared with CFU-GM from normal individuals. One supernatant from a noncytotoxic T cell line stimulated CFU-GM and was demonstrated by antibody neutralization studies to contain interleukin-3 (IL-3) and GM-CSF. These data indicate that alloreacting CD4 cells exert both cytotoxic and cytokine-mediated antileukemia effects which may relate to the graft-vs.-leukemia (GVL) effect in CML following bone marrow transplantation.
Proteinases 1: lysosomal cysteine proteinases.
Explore the source record for details and available documents.
Comparison of helper and cytotoxic antirecipient T cell frequencies in unrelated bone marrow transplantation.
Donor/recipient histocompatibility antigen differences initiate acute graft-versus-host disease (GVHD) after bone marrow transplantation. Frequency analysis, using limiting dilution techniques, of functionally defined (helper or cytotoxic) antirecipient T lymphocyte precursors in the peripheral blood of the donor has been shown to be an accurate predictor for the development of moderate-to-severe acute GVHD. Here, we describe a sensitive assay for measuring alloreactive helper (IL-2-producing) T lymphocyte precursor (HTLp) frequencies, and compare the ability of this assay and the cytotoxic T lymphocyte precursor (CTLp) assay to detect HLA- class II and class I differences and to predict clinical outcome in a cohort of unrelated donor/recipient BMT pairs. Twenty-two pairs underwent unrelated donor BMT. Patients with high (> 1:100 x 10(3)) HTLp or CTLp frequencies had a higher incidence of moderate-to-severe (grades II-IV) acute GVHD (80% and 100%, respectively) than pairs with low (< 1:100 x 10(3)) frequencies (40% and 57%, respectively). Ten (45%) patients have died, but all patients with both a low HTLp and low CTLp frequency remain alive. The HTLp and CTLp assays provided similar predictive information for outcome. Given that the HTLp assay is more rapid and less labor intensive, it offers an additional or alternative functional method for donor selection in unrelated donor BMT.
Bone marrow transplants from HLA-identical siblings as compared with chemotherapy for children with acute lymphoblastic leukemia in a second remission.
BACKGROUND: It is unclear how best to treat children with acute lymphoblastic leukemia who are in a second remission after a bone marrow relapse. For those with HLA-identical siblings, the question of whether to perform a bone marrow transplantation or to continue chemotherapy has not been answered. METHODS: We compared the results of treatment with marrow transplants from HLA-identical siblings in 376 children, as reported to the International Bone Marrow Transplant Registry, with the results of chemotherapy in 540 children treated by the Pediatric Oncology Group. A preliminary analysis identified variables associated with treatment failure in both groups. We selected cohorts by matching these variables. A possible bias associated with differences in the interval between remission and treatment was controlled for by choosing matched pairs in which the duration of the second remission in the chemotherapy recipient was at least as long as the time between the second remission and transplantation in the transplant recipient. A total of 255 matched pairs were studied. RESULTS: The mean (+/- SE) probability of a relapse at five years was significantly lower among the transplant recipients than among the chemotherapy recipients (45 +/- 4 percent vs. 80 +/- 3 percent, P < 0.001). At five years the probability of leukemia-free survival was higher after transplantation than after chemotherapy (40 +/- 3 percent vs. 17 +/- 3 percent, P < 0.001). The relative benefit of transplantation as compared with chemotherapy was similar in children with prognostic factors indicating a high or low risk of relapse (the duration of the first remission, age, leukocyte count at the time of the diagnosis, and phenotype of the leukemic cells). CONCLUSIONS: For children with acute lymphoblastic leukemia in a second remission, bone marrow transplants from HLA-identical siblings result in fewer relapses and longer leukemia-free survival than does chemotherapy.
The possible role of neutrophil proteinases in damage to articular cartilage. 1978.
Explore the source record for details and available documents.
Classification of peptidases.
Explore the source record for details and available documents.
Families of serine peptidases.
Explore the source record for details and available documents.
Families of cysteine peptidases.
Explore the source record for details and available documents.
Bone marrow transplantation for acute lymphoblastic leukaemia.
Allogeneic bone marrow transplantation (BMT) has been used in the treatment of poor risk acute lymphoblastic leukaemia (ALL) for over 20 years. Over this period results have improved and indications for treatment have become more clearly defined. Over 60% of adults and over 70% of children with poor risk ALL in first remission, and 30-40% of patients in second remissions can be expected to achieve long term leukaemia-free survival. Factors implicated in the cure of ALL by BMT are the myeloablative preparative regimen, a graft-versus-leukaemia effect, and post transplant chemotherapy. Improved results of chemotherapy have changed the perceived indications for BMT in ALL and have led to controversy over the best treatment approach. However there is good evidence to show that BMT offers a better chance of leukaemia free survival in certain very poor risk categories. These include Philadelphia chromosome positive ALL, remission induction failures, and children in second remission who relapse after adequate chemotherapy. Particular issues in the use of BMT in ALL are the prevention and management of extramedullary leukaemia, the treatment of relapse following BMT, and the prevention and monitoring of late effects. In the future the use of unrelated donors, and a continuing fall in transplant related morbidity and mortality will extend the use of BMT in poor risk ALL.
Distinct T cell populations distinguish chronic myeloid leukaemia cells from lymphocytes in the same individual: a model for separating GVHD from GVL reactions.
Donor lymphocyte responses to minor histocompatibility antigen (mHA) differences are involved in allo-responses between HLA matched pairs causing GVHD and graft-versus-leukaemia (GVL). Since some mHA are tissue-restricted, GVHD and GVL responses may be separable. We studied donor lymphocyte responses to patients with CML in a series of 10 HLA-matched sibling and 10 unrelated donor-recipient pairs comparing proliferation to recipient PHA blasts and CML cells and attempting to selectively deplete responses to PHA blasts in vitro. Responses in counts per min (c.p.m) to CML cells and PHA blasts were, respectively, 2809 +/- 2205 (SD) and 7376 +/- 1877 in related and 12,107 +/- 7191 and 26,136 +/- 22,479 in unrelated pairs. Autologous responses to PHA blasts were significantly lower (mean 779 +/- 735) (p < 0.001). Results correlated with clinical outcome: higher responses to recipient cells correlated with transplant-related death (p = 0.02 for CML and p = 0.06 for PHA blasts). Higher responses to CML correlated with GVHD grade > or = II (p = 0.025). Donor lymphocytes exposed to recipient PHA blasts for 5 days and treated with a ricin-conjugated anti-CD25 antibody retained over 75% of their response to CML but < 10% to PHA blasts. Similarly, depletion of response to CML but not to PHA blasts occurred when CML was the primary challenge. These results indicate that distinct populations of donor T cells respond to recipient leukaemic and non-leukaemic cells, and provide the basis for a clinically applicable technique to selectively deplete donor GVHD reacting cells while conserving GVL.
Minimal residual disease after bone marrow transplantation for chronic myelogenous leukemia and implications for graft-versus-leukemia effect: a review of recent results.
Cure of leukemia by allogeneic BMT is achieved by the combined effect of the myeloablative preparative regimen and an allo-immune response of donor cells to residual leukemia termed the graft-versus-leukemia (GVL) effect. In the first year following BMT for CML, PCR used to detect the leukemia-specific BCR/ABL message frequently reveals subclinical levels of persisting leukemia. In a meta-analysis of reports on qualitative PCR findings after BMT for CML in 12 recently published series, we found that for unmanipulated BMT in chronic phase, PCR detection was not associated with a higher relapse risk and that most patients became PCR negative within 2 years post-BMT. In contrast, PCR detection of BCR/ABL transcripts was a more reliable predictor in recipients of T cell-depleted BMT and in those transplanted in accelerated or blastic phase of their disease. For accurate prediction of relapse, serial quantitative PCR is necessary. It could also be used to monitor efficacy of experimental treatments of relapse with interferon or donor lymphocyte transfusions. Furthermore, studies of the association of GVHD with PCR detection of BCR/ABL message may shed light on the relationship of GVL with minimal residual disease in CML.
Binding of BCR/ABL junctional peptides to major histocompatibility complex (MHC) class I molecules: studies in antigen-processing defective cell lines.
Leukaemia-specific proteins may be recognized by T-lymphocytes as neoantigens if peptides corresponding to mutated sequences bind to major histocompatibility complex (MHC) molecules on leukaemic cells. We studied the ability of a series of synthetic peptides corresponding to the junctional sequences of BCR/ABL proteins to bind to class I molecules in two human cell lines, LBL 721.174 (T2) (HLA-A2, B5) and BM36.1 (HLA-A1, B35), and one murine cell line RMA-S (H-2Kb, Db). These cell lines are defective in intracellular peptide loading of class I molecules, resulting in markedly reduced cell surface class I expression: class I expression can be rescued by provision of peptides binding to the alleles expressed by the mutant cell. Eighteen peptides spanning the junctional sequences of the b2a2 and b3a2 proteins were tested for their ability to rescue expression of the class I alleles borne by these cells using flow cytometry. Allele-specific control peptides known to bind HLA-A2, HLA-B35, H-2Kb and H-2Db increased expression of these alleles 2- to 3-fold: 0/18 BCR/ABL peptides enhanced HLA-A2, HLA-B35 or H-2Kb expression, but three b2a2 peptides consistently increased H-2Db expression. These results suggest that BCR/ABL junctional peptides are unlikely to be presented to T-cells in association with HLA-A2, HLA-B35 or H-2Kb. Conversely, the finding that some b2a2 peptides bind specifically to H-2Db suggests that a murine model of graft-versus-leukaemia (GVL) could be constructed.
Thimet oligopeptidase: similarity to 'soluble angiotensin II-binding protein' and some corrections to the published amino acid sequence of the rat testis enzyme.
The deduced amino acid sequence of pig liver soluble angiotensin II-binding protein [Sugiura, Hagiwara and Hirose (1992) J. Biol. Chem. 267, 18067-18072] is similar over most of its length to that reported for rat testis thimet oligopeptidase (EC 3.4.24.15) by Pierotti, Dong, Glucksman, Orlowski and Roberts [(1990) (Biochemistry 29, 10323-10329]. We have found that homogeneous rat testis thimet oligopeptidase binds angiotensin II with the same distinctive characteristics as the pig liver protein. Analysis of the nucleotide sequences reported for the two proteins pointed to the likelihood that sequencing errors had caused two segments of the amino acid sequence of the rat protein to be translated out of frame, and re-sequencing of selected parts of the clone (kindly provided by the previous authors) confirmed this. The revised deduced amino acid sequence of rat thimet oligopeptidase contains 687 residues, representing a protein of 78,308 Da, and is more closely related to those of the pig liver protein and other known homologues of thimet oligopeptidase than that described previously.
Human thimet oligopeptidase.
We have purified human thimet oligopeptidase to homogeneity from erythrocytes, and compared it with the enzyme from rat testis and chicken liver. An antiserum raised against rat thimet oligopeptidase also recognized the human and chicken enzymes, suggesting that the structure of the enzyme has been strongly conserved in evolution. Consistent with this, the properties of the human enzyme were very similar to those for the other species. Thus human thimet oligopeptidase also is a thiol-dependent metallo-oligopeptidase with M(r) about 75,000. Specificity for cleavage of a number of peptides was indistinguishable from that of the rat enzyme, but Ki values for the four potent reversible inhibitors tested were lower. In discussing the results, we consider the determinants of the complex substrate specificity of thimet oligopeptidase. We question whether substrates containing more than 17 amino acid residues are cleaved, as has been suggested. We also point out that the favourable location of a proline residue and a free C-terminus in the substrate may be as important as the hydrophobic residues in the P2, P1 and P3' positions that have been emphasized in the past.
Allogeneic bone marrow transplantation for chronic myeloid leukemia using sibling and volunteer unrelated donors. A comparison of complications in the first 2 years.
OBJECTIVE: To compare the short- and medium-term complications (particularly infection) of bone marrow transplantation for chronic myeloid leukemia in patients with HLA-identical sibling donors or volunteer unrelated donors. DESIGN: Retrospective review of two cohorts of patients. SETTING: Tertiary referral center. PATIENTS: One hundred three patients with chronic myeloid leukemia in first chronic phase. INTERVENTION: Patients were treated with bone marrow transplantation using marrow from HLA-identical siblings (n = 57) and volunteer donors (n = 46). MAIN RESULTS: In total, 68 patients survived a median of 22 months from bone marrow transplant (range, 7 to 81 months). The actuarial probabilities of overall survival and leukemia-free survival at 2 years for the sibling donor group were 73% (95% CI, 60% to 86%) and 72% (CI, 60% to 84%), respectively, and for the volunteer donor group, 47% (CI, 31% to 63%) and 42% (CI, 26% to 58%) (P = 0.07 and 0.05, respectively). However, after adjustment for duration of disease, overall and disease-free survival in the two donor groups did not differ significantly. A major problem was an increased incidence of severe viral infection in the volunteer unrelated donor group (19 episodes in 16 of 46 patients compared with 7 episodes in 7 of 57 sibling donor patients, P = 0.01). The actuarial incidence of chronic graft-versus-host disease (GVHD) was higher in volunteer unrelated donor patients (77% [CI, 63% to 91%] compared with 49% [CI, 35% to 63%]; P = 0.02) but that of acute GVHD was not. The median performance status of the survivors in the volunteer donor group is similar to that in the sibling donor group. The incidence of hematologic relapse in both groups so far is low. CONCLUSION: Results appear to justify the continued use of volunteer donors in chronic-phase chronic myeloid leukemia, but infection and chronic GVHD are still major problems.
Autonomous growth of blast cells is associated with reduced survival in acute myeloblastic leukemia.
We have previously classified the in vitro growth characteristics of clonogenic blasts from patients with acute myeloblastic leukemia (AML) according to their capacity to proliferate autonomously in a blast cell colony assay. Here we have analyzed whether the presence of in vitro autonomous growth characteristics has any clinical relevance in AML. We have studied 50 patients (age 2 to 64 years), all of whom were treated with combination chemotherapy, excluding patients with a history of antecedent myelodysplasia. Leukemic cells from 34 of 50 patients (68%) exhibited either partial or totally autonomous growth in a blast cell colony assay. Cells from the remaining patients exhibited nonautonomous growth and were either totally dependent on exogenous growth factor (n = 8) or failed to proliferate at all in the culture system used (n = 8). All 50 patients were treated by intensive chemotherapy and 69% achieved complete remission (CR). Patients whose blasts exhibited autonomous growth in vitro had a significantly lower CR rate (57%) compared with the 16 patients with nonautonomous growth (94%, P = .02). White blood cell count was the only other significant factor (P = .03), but in multivariate analysis growth characteristics remains the most important predictor of CR. Actuarial relapse risk is 80% and 42% at 5 years for autonomous and nonautonomous groups respectively (P = .1). Overall disease-free survival is 21.8% and is higher in the nonautonomous growth group at 54.2% compared with 11.3% at 5 years (P = .0015) in the autonomous growth characteristics was found to be the single most important indicator of CR and disease-free survival. Our data suggests that the suppression of autocrine growth factor production may be of value in the treatment of AML.
Characterization of the bacterial metalloendopeptidase pitrilysin by use of a continuous fluorescence assay.
Pitrilysin (EC 3.4.99.44) has been purified from an over-expressing strain of Escherichia coli. A 13-residue quenched-fluorescent-peptide substrate for the enzyme has been synthesized, and found also to be cleaved by the homologous enzyme, insulinase (EC 3.4.99.45). The action of pitrilysin on peptides and proteins was studied: insulin B chain was the most rapidly degraded, small peptides down to 10 residues in length were cleaved more slowly, intact insulin was cleaved very slowly but with a very low Km, and there was no action on the larger proteins tested. Since the activity of pitrilysin is confined to substrates smaller than proteins, it can be described as an endopeptidase of the 'oligopeptidase' type, and like other such enzymes, it did not interact with alpha 2-macroglobulin. The metal-dependence of pitrilysin was confirmed, and it was found to be inhibited by bacitracin, especially in the presence of zinc.