Search for Gamma-Ray Spectral Lines from Dark Matter Annihilation up to 100 TeV toward the Galactic Center with MAGIC

Linelike features in TeV γ rays constitute a "smoking gun" for TeV-scale particle dark matter and new physics. Probing the Galactic Center region with ground-based Cherenkov telescopes enables the search for TeV spectral features in immediate association with a dense dark matter reservoir at a sensitivity out of reach for satellite γ-ray detectors, and direct detection and collider experiments. We report on 223 hours of observations of the Galactic Center region with the MAGIC stereoscopic telescope system reaching γ-ray energies up to 100 TeV. We improved the sensitivity to spectral lines at high energies using large-zenith-angle observations and a novel background modeling method within a maximum-likelihood analysis in the energy domain. No linelike spectral feature is found in our analysis. Therefore, we constrain the cross section for dark matter annihilation into two photons to ⟨σv⟩≲5×10^{-28}  cm^{3} s^{-1} at 1 TeV and ⟨σv⟩≲1×10^{-25}  cm^{3} s^{-1} at 100 TeV, achieving the best limits to date for a dark matter mass above 20 TeV and a cuspy dark matter profile at the Galactic Center. Finally, we use the derived limits for both cuspy and cored dark matter profiles to constrain supersymmetric wino models.

Bounds on Lorentz Invariance Violation from MAGIC Observation of GRB 190114C

On January 14, 2019, the Major Atmospheric Gamma Imaging Cherenkov telescopes detected GRB 190114C above 0.2 TeV, recording the most energetic photons ever observed from a gamma-ray burst. We use this unique observation to probe an energy dependence of the speed of light in vacuo for photons as predicted by several quantum gravity models. Based on a set of assumptions on the possible intrinsic spectral and temporal evolution, we obtain competitive lower limits on the quadratic leading order of speed of light modification.

Fludarabine as a cost-effective adjuvant to enhance engraftment of human normal and malignant hematopoiesis in immunodeficient mice

There is still an unmet need for xenotransplantation models that efficiently recapitulate normal and malignant human hematopoiesis. Indeed, there are a number of strategies to generate humanized mice and specific protocols, including techniques to optimize the cytokine environment of recipient mice and drug alternatives or complementary to the standard conditioning regimens, that can be significantly modulated. Unfortunately, the high costs related to the use of sophisticated mouse models may limit the application of these models to studies that require an extensive experimental design. Here, using an affordable and convenient method, we demonstrate that the administration of fludarabine (Fludara^TM) promotes the extensive and rapid engraftment of human normal hematopoiesis in immunodeficient mice. Quantification of human CD45⁺ cells in bone marrow revealed approximately a 10²-fold increase in mice conditioned with irradiation plus fludarabine. Engrafted cells in the bone marrow included hematopoietic stem cells, as well as myeloid and lymphoid cells. Moreover, this model proved to be sufficient for robust reconstitution of malignant myeloid hematopoiesis, permitting primary acute myeloid leukemia cells to engraft as early as 8 weeks after the transplant. Overall, these results present a novel and affordable model for engraftment of human normal and malignant hematopoiesis in immunodeficient mice.

Monomeric, porous type II collagen scaffolds promote chondrogenic differentiation of human bone marrow mesenchymal stem cells in vitro

Osteoarthritis (OA) is a common cause of pain and disability and is often associated with the degeneration of articular cartilage. Lesions to the articular surface, which are thought to progress to OA, have the potential to be repaired using tissue engineering strategies; however, it remains challenging to instruct cell differentiation within a scaffold to produce tissue with appropriate structural, chemical and mechanical properties. We aimed to address this by driving progenitor cells to adopt a chondrogenic phenotype through the tailoring of scaffold composition and physical properties. Monomeric type-I and type-II collagen scaffolds, which avoid potential immunogenicity associated with fibrillar collagens, were fabricated with and without chondroitin sulfate (CS) and their ability to stimulate the chondrogenic differentiation of human bone marrow-derived mesenchymal stem cells was assessed. Immunohistochemical analyses showed that cells produced abundant collagen type-II on type-II scaffolds and collagen type-I on type-I scaffolds. Gene expression analyses indicated that the addition of CS - which was released from scaffolds quickly - significantly upregulated expression of type II collagen, compared to type-I and pure type-II scaffolds. We conclude that collagen type-II and CS can be used to promote a more chondrogenic phenotype in the absence of growth factors, potentially providing an eventual therapy to prevent OA.

The diagnostic classification of eating disorders: current situation, possible alternatives and future perspectives

The current nosography of eating disorders (ED) has various limitations in terms of validity and accuracy. The changes adopted in the DSM-5 limit some of the current problems, such as excessive prevalence of ED not otherwise specified (EDNOS) and the lack of longitudinal stability, but are unlikely to adequately capture the clinical complexity of ED. Many authors suggest the need for a thorough review of the current nosography to support evidence-based classification. In this paper, we discuss the validity of the current diagnostic categories and their possible reorganization. Furthermore, we review the main empirical models of classification and the diagnostic approach from a personality perspective, with particular attention to research and to the prognostic and therapeutic implications.

Prolonged duodenal paralysis after PEG placement in a patient with traumatic brain injury: a case report

Percutaneous endoscopic gastrostomy (PEG) has recently become a usual procedure for patients with prolonged disorders of consciousness after brain injuries. Despite a high rate of success and a very low procedure-related mortality, morbidity associated to PEG placement reaches 9.4% in a recent large meta-analysis. This case report describes an uncommon complication of PEG placement in a patient with vegetative state after traumatic brain injury: the development of prolonged duodenal paralysis. This patient was treated by placement of a transient jejunostomy until recovery of duodenal functional activity, to permit adequate nutrition. This procedure-related complication is previously unreported in scientific literature.

Basic research and clinical applications of non-hematopoietic stem cells, 4-5 April 2008, Tubingen, Germany

From 4 to 5 April 2008, international experts met for the second time in Tubingen, Germany, to present and discuss the latest proceedings in research on non-hematopoietic stem cells (NHSC). This report presents issues of basic research including characterization, isolation, good manufacturing practice (GMP)-like production and imaging as well as clinical applications focusing on the regenerative and immunomodulatory capacities of NHSC.

Haemopoietic stem cell transplantation induces tolerance to donor antigens but not to foreign FVIII peptides

A 22-year-old male with severe haemophilia A and high responding factor VIII (FVIII) inhibitor underwent sibling haematopoietic stem cell transplantation in an attempt to eradicate the inhibitor. A reduced intensity conditioning regimen was followed by bone marrow infusion and continuous FVIII administration during immune reconstitution. Although substantial levels of FVIII:C (>100 IU dL(-1)) were maintained initially, at day +23 inhibitor titres rose, indicating boosting of recipient memory repertoire, despite complete donor chimerism. On day +46, he developed Klebsiella pneumoniae septicaemia and died. This case shows that, despite very successful transplantation tolerance, the procedure failed to control long-term memory effector immune cells.

Long-term clinical results of autologous infusion of mobilized adult bone marrow derived CD34+ cells in patients with chronic liver disease

Evidence is growing in support of the role of stem cells as an attractive alternative in treatment of liver diseases. Recently, we have demonstrated the feasibility and safety of infusing CD34(+) adult stem cells; this was performed on five patients with chronic liver disease. Here, we present the results of long-term follow-up of these patients. Between 1 x 10(6) and 2 x 10(8) CD34(+) cells were isolated and injected into the portal vein or hepatic artery. The patients were monitored for side effects, toxicity and changes in clinical, haematological and biochemical parameters; they were followed up for 12-18 months. All patients tolerated the treatment protocol well without any complications or side effects related to the procedure, also there were no side effects noted on long-term follow-up. Four patients showed an initial improvement in serum bilirubin level, which was maintained for up to 6 months. There was marginal increase in serum bilirubin in three of the patients at 12 months, while the fourth patient's serum bilirubin increased only at 18 months post-infusion. Computed tomography scan and serum alpha-foetoprotein monitoring showed absence of focal lesions. The study indicated that the stem cell product used was safe in the short and over long term, by absence of tumour formation. The investigation also illustrated that the beneficial effect seemed to last for around 12 months. This trial shows that stem cell therapy may have potential as a possible future therapeutic protocol in liver regeneration.

The highway code of T cell trafficking

Coordinated migratory events are required for the development of effective and regulated immunity. Naïve T lymphocytes are programmed to recirculate predominantly in secondary lymphoid tissue by non-specific stimuli. In contrast, primed T cells must identify specific sites of antigen location in non-lymphoid tissue to exert targeted effector responses. Following priming, T cells acquire the ability to establish molecular interactions mediated by tissue-selective integrins and chemokine receptors (homing receptors) that allow their access to specific organs, such as the skin and the gut. Recent studies have shown that an additional level of specificity is provided by the induction of specific T cell migration into the tissue following recognition of antigen displayed by the endothelium. In addition, co-stimulatory signals (such as those induced by CD28 and CTLA-4 molecules) have been shown not only to regulate T cell activation and differentiation, but also to orchestrate the anatomy of the ensuing T cell response.

Mesenchymal stem cells of cord blood origin are effective at preventing but not treating graft-versus-host disease

The immunosuppressive properties of mesenchymal stem cells (MSC) make them particularly attractive to manipulate graft-versus-host disease (GVHD). So far, the experience of using MSC to treat GVHD is limited to a few cases, controversial results come from preclinical models and several issues remain to be clarified. The present studies were designed to address these questions in a xenogenic model testing the ability of umbilical cord blood-derived MSC (UCB-MSC) to prevent and/or treat GVHD. Sublethally irradiatiated non-obese diabetic/severe combined immunodeficiency NOD/SCID mice transplanted with human peripheral blood mononuclear cells (huPBMC) showed extensive human T-cell proliferation in the peripheral blood, lymphoid and non-lymphoid tissues, which evolved in extensive GVHD (wasting, ruffled hair and hunched back). The mice treated with a single dose of UCB-MSC did not behave differently form the controls. However, when UCB-MSC were given at weekly intervals, there was a marked decrease in human T-cell proliferation and none of the mice developed GVHD. No therapeutic effect was obtained if UCB-MSC were administered at onset of GVHD. This work supports the clinical use of MSC in stem cell transplantation as a prophylaxis rather than treatment of GVHD.

Disease relapse after haematopoietic stem cell transplantation: Risk factors and treatment

Disease relapse is the commonest cause of treatment failure after allogeneic haematopoietic stem-cell transplantation. Adoptive immunotherapy based on donor lymphocyte infusions (DLI) has a prominent role in the management of disease recurrence. Although the highest remission rates are achieved in chronic myeloid leukaemia (CML), encouraging results have also been reported in chronic lymphoproliferative disorders. However, the experience of DLI in CML is not necessarily applicable to the management of lymphoproliferative diseases because of the heterogeneity of the conditioning regimens used in chronic lymphoid malignancies. We will review the role of DLI for different disease types in the context of conventional and reduced-intensity conditioning regimens. The factors influencing response and graft-versus-host disease as well as the optimal cell dose will be discussed. Finally, we will describe the main avenues currently being explored to improve the selectivity and efficacy of DLI.

Factors for graft-versus-host disease after donor lymphocyte infusions with an escalating dose regimen: lack of association with cell dose

We investigated the risk factors for graft-versus-host disease (GVHD) in 82 patients treated with donor lymphocyte infusions (DLI) using an escalating dose regimen for chronic myeloid leukaemia in relapse following conventional allografting. Two factors emerged as predictors of both acute and chronic GVHD: the infusion of male recipients with lymphocytes from a female donor and the interval between transplant and last DLI, but only the first remained significant at multivariate analysis. Surprisingly, lymphocyte dose did not influence the incidence of GVHD. Our results suggest that DLI can be given in large cell doses without increasing the risk of GVHD.

Response to donor lymphocyte infusions for chronic myeloid leukemia is dose-dependent: the importance of escalating the cell dose to maximize therapeutic efficacy

Donor lymphocyte infusions (DLI) are an effective treatment for patients with chronic myeloid leukemia (CML) in relapse after allografting but the optimal cell dose has yet to be identified. To address this question, we investigated the factors affecting the dose required to achieve remission (effective cell dose, (ECD)) in 81 patients treated with an escalating dose regimen. The overall proportion of patients who achieved a molecular remission was 88%. The cumulative proportion of remitters increased significantly at each dose level. With a CD3(+) cell dose < or =10(7)/kg, 56% of patients in molecular/cytogenetic relapse obtained molecular remission, whereas only 20% of those in hematologic relapse did so. At the same cell dose, 58% of patients who received lymphocytes from volunteer unrelated donors achieved remission, as compared to 29% of those who received DLI from sibling donors. We conclude that the response to DLI is dose-dependent and that the ECD is influenced by the quantity and phase of CML at relapse and degree of donor/recipient histocompatibility.

Increased frequencies of CD4(+)CD25(high) T(regs) correlate with disease relapse after allogeneic stem cell transplantation for chronic myeloid leukemia

The therapeutic efficacy of allogeneic hemopoietic stem cell transplantation (SCT) for chronic myeloid leukemia (CML) largely relies on the graft-versus-leukemia (GvL) effect exerted by donor T cells. CD4(+)CD25(high) regulatory T cells (T(regs)) have been shown to downregulate antitumor responses but their role on GvL has not been evaluated. We performed a cross-sectional study in which we enumerated and characterized CD4(+)CD25(high) T(regs) in the peripheral blood of CML patients undergoing allogeneic SCT. We documented higher frequencies of T(regs) in patients after transplant as compared to normal controls and newly diagnosed patients. The increment was particularly evident in patients who had received their SCT 18 months before. In vitro functional studies demonstrated that the T(regs) purified from SCT patients exhibited a more potent suppressive activity than T(regs) isolated from healthy volunteers. Patients in whom T(regs) numbers were higher than controls more than 18 months after SCT showed evidence of disease relapse. Although the increment in T(regs) might have an advantageous effect on graft rejection in the early phase post-transplant, our data suggest that T(regs) exert an inhibitory effect on GvL.

Mesenchymal stem cells inhibit proliferation and apoptosis of tumor cells: impact on in vivo tumor growth

Mesenchymal stem cells (MSC) have received much attention in the field of hematopoietic stem cell transplantation because not only do they support hematopoiesis but also exhibit a profound immunosuppressive activity that can be exploited to prevent undesired alloreactivity. We have previously shown that their immunosuppressive activity is mainly exerted at the level of T-cell proliferation. Here, we show that MSC exhibit a similar antiproliferative activity on tumor cells of hematopoietic and non hematopoietic origin. In vitro, MSC produced the transient arrest of tumor cells in the G(1) phase of cell cycle; this was accompanied by a reduction in the apoptotic rate even when survival factors were limiting. However, when tumor cells were injected into non-obese diabetic-severe combined immunodeficient mice in conjunction with MSC, their growth was much faster as compared to the group receiving only tumor cells. To explain the discrepancy between the in vitro and in vivo behavior, we suggest that MSC have the ability to form a cancer stem cell niche in which tumor cells can preserve the potential to proliferate and sustain the malignant process. We conclude that the clinical use of MSC in conditions in which a malignant disease is involved should be handled with extreme caution.

Variable Very-High-Energy Gamma-Ray Emission from the Microquasar LS I +61 303

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes.

Management of chronic myeloid leukaemia in relapse following donor lymphocyte infusion induced remission: a retrospective study of the clinical trials committee of the British Society of Blood & Marrow Transplantation (BSBMT)

Donor lymphocyte infusion (DLI) can restore remission in a high percentage of patients with chronic myeloid leukaemia (CML) who relapse after allogeneic stem cell transplant (SCT). Subsequent relapses after a DLI-induced remission do occur and the optimal management of these patients is not defined. A retrospective study of the practice of UK transplant centres was conducted. In all, 13 patients from seven centres were identified: all were treated for relapse post allogeneic SCT with DLI and achieved either a complete cytogenetic (n=5) or molecular (n=8) remission. All patients subsequently had a second relapse, at molecular (n=7), cytogenetic (n=4) and haematological (n=2) levels. Further DLI was used in the treatment of 11 patients, imatinib mesylate in three and chemotherapy in two. The two patients with haematological relapse died of blastic disease. The remaining 11 patients achieved either a complete cytogenetic (n=2) or molecular (n=9) remission. Nine patients remain in molecular remission at a median follow-up of 29 months, seven of whom had received DLI alone as treatment for second relapse, one DLI plus imatinib and one imatinib alone. Toxicity following DLI for second relapse was low. Longer follow-up will be required to see if these second DLI-induced remissions will be durable.

Monitoring patients in complete cytogenetic remission after treatment of CML in chronic phase with imatinib: patterns of residual leukaemia and prognostic factors for cytogenetic relapse

We monitored BCR-ABL transcript levels by quantitative real-time PCR in 103 patients treated with imatinib for chronic myeloid leukaemia in chronic phase for a median of 30.3 months (range 5.5-49.9) after they achieved complete cytogenetic remission (CCyR). The patients could be divided into three groups: (1) in 32 patients transcript levels continued to decline during the period of observation (nadir BCR-ABL/ABL ratio 0.015%); in five of these patients BCR-ABL transcripts became undetectable on repeated testing, (2) in 42 patients the transcript levels reached a plateau and (3) in 26 patients transcript numbers increased and the initial CCyR was lost. Three patients were not evaluable. Patients who remained in CCyR for at least 24 months appeared to have a low risk of subsequent cytogenetic relapse. We conclude that the pattern of 'residual' disease after achieving CCyR on imatinib is variable: some patients in CCyR show a progressive reduction in the level of residual disease, some reach a plateau where transcript numbers are relatively stable and others relapse with Ph-positive metaphases.

Imatinib inhibits the activation and proliferation of normal T lymphocytes in vitro

The ABL tyrosine kinase inhibitor imatinib mesylate is highly effective in the treatment of CML and is increasingly used in the stem cell transplantation (SCT) setting. Since ABL-dependent intracellular signaling molecules are involved in T-cell activation, imatinib may affect T-cell responses in vivo, thus affecting T-cell function in CML patients, disrupting immune reconstitution after allogeneic SCT and/or impeding the graft-versus-leukemia effect. Here we demonstrate that imatinib inhibits PHA-induced proliferation of normal peripheral blood mononuclear cells at in vitro concentrations (1-5 micromol/l) representative of the pharmacological doses used therapeutically in vivo. The effect is not dependent on antigen-presenting cells because CD3/CD28-induced T-cell stimulation was similarly inhibited by imatinib. Dose-dependent inhibition of the proliferative response of purified CD8+ and CD4+ T lymphocytes to anti-CD3/CD28 was similarly observed and associated with reduction in IFN-gamma production. The inhibitory effect could not be ascribed to an increased rate of apoptosis but the expression of activation markers on CD3+ T cells was significantly reduced in the presence of imatinib (1-5 micromol/L). Inhibition of T-cell proliferation was reversible after removal of the drug from the cultures. Thus, imatinib inhibits T-cell proliferation in vitro, an effect that is APC-independent, reversible, and does not involve apoptosis induction.

[An unexpected bottleneck]

This is a clinical case concerning an uremic female patient who presented with an important oedema in the omolateral left arm, after the creation of an AV fistula. All the diagnostic procedures including the ultrasound color-Doppler were irrelevant. The patient was positive for a subclavian venous stenosis which was completely unexpected. This clinical case questions how useful it is in indirectly evaluating flow meters by ultrasound color-Doppler in the work-up of central venous steno-occlusions.

Minor H antigens: genes and peptides

In this review, we describe the evidence from which the existence of non-MHC histocompatibility (H) antigens was deduced, the clinical setting of bone marrow transplantation in which they are important targets for T cell responses, and the current understanding of their molecular identity. We list the peptide epitopes, their MHC restriction molecules and the genes encoding them, of the human and murine minor H antigens now identified at the molecular level. Identification of the peptide epitopes allows T cell responses to these antigens following transplantation of MHC-matched, minor H-mismatched tissues to be enumerated using tetramers and elispot assays. This will facilitate analysis of correlations with HVG, GVH and GVL reactions in vivo. The potential to use minor H peptides to modulate in vivo responses to minor H antigens is discussed. Factors controlling immunodominance of T cell responses to one or a few of many potential minor H antigens remain to be elucidated but are important for making predictions of in vivo HVG, GVH and GVL responses and tailoring therapy after HLA-matched BMT and DLI.

Normal and chronic phase CML hematopoietic cells repopulate NOD/SCID bone marrow with different kinetics and cell lineage representation

INTRODUCTION

Chronic myelogenous leukemia is characterized by a clonal expansion of abnormal hematopoietic cells, which eventually replaces normal hematopoiesis. We wanted to test the hypothesis that the growth kinetics of CML and normal hematopoietic cells are different.

MATERIALS AND METHODS

We compared the growth kinetics and the phenotype of engraftment of chronic phase CML and normal human CD34(+) precursor cells in the bone marrow of immune deficient mice.

RESULTS

High levels of engraftment of normal precursors occurred early and consisted of myeloid, erythroid, megakaryocytic, and lymphoid elements. This level and pattern of engraftment were maintained at later assessments. The level of CML cell engraftment was initially much lower, but it increased progressively at late time-points with no indication of a plateau in growth. Early engraftment of CML cells consisted almost entirely of myeloid and mast cells but soon after only mast cells were detectable. Conversely mast cells were infrequent in mice engrafted with normal progenitors.

CONCLUSION

We conclude that in contrast to normal cell engraftment, engraftment of CML cells in NOD/SCID mice is characterized by a slow but progressive myeloid infiltration, which eventually consists almost entirely of mast cells.

Molecular studies in patients with chronic myeloid leukaemia in remission 5 years after allogeneic stem cell transplant define the risk of subsequent relapse

We identified 103 consecutive patients who, 5 years after allogeneic transplantation for chronic myeloid leukaemia (CML), were in molecular remission (MR). The 103 patients were divided into three groups on the basis of reverse transcription-polymerase chain reaction (RT-PCR) studies for BCR-ABL transcripts in the first 5 years post transplant: Group A comprised 63 patients who had been continuously PCR negative; Group B comprised 20 patients with one or more positive PCR result but only at a low level; and Group C comprised 20 patients who had fulfilled the criteria for molecular relapse, been treated with donor lymphocyte infusions (DLI) and had thereafter regained complete MR within the 5-year post-transplant period. The median follow-up for all 103 patients was 8.4 years from transplant (range 5-17.6 years). In group A only one patient relapsed at 9.2 years. In group B eight patients (40%) relapsed: six at molecular, one at cytogenetic and one haematological levels. The actuarial probabilities of survival at 10 years for patients in Groups A, B and C were 97.4%, 92.9% and 100% respectively; the probabilities of relapse were 3%, 54% and 0% respectively. We conclude that molecular studies during the first 5 years post transplant can help to predict long-term leukaemia-free survival and, possibly, cure of CML.

Minor H antigens: genes and peptides

In this review, we describe the evidence from which the existence of non-MHC histocompatibility (H) antigens was deduced, the clinical setting of bone marrow transplantation in which they are important targets for T-cell responses, and the current understanding of their molecular identity. We list the peptide epitopes of the human and murine minor H antigens now identified at the molecular level, their MHC restriction molecules and the genes encoding them. Identification of the peptide epitopes allows T-cell responses to these antigens following transplantation of MHC-matched, minor H-mismatched tissues to be enumerated using tetramers and elispot assays. This will facilitate analysis of correlations with host-versus-graft (HVG), graft-versus-host (GVH) and graft-versus-leukaemia (GVL) reactions in vivo. The potential to use minor H peptides to modulate in vivo responses to minor H antigens is discussed. Factors controlling immunodominance of T-cell responses to one or a few of many potential minor H antigens remain to be elucidated but are important for making predictions of in vivo HVG, GVH and GVL responses and tailoring therapy after HLA-matched bone marrow transplantation and donor lymphocyte infusion.

Examination of HY response: T cell expansion, immunodominance, and cross-priming revealed by HY tetramer analysis

We have applied MHC class I tetramers representing the two H2(b) MHC class I-restricted epitopes of the mouse male-specific minor transplantation Ag, HY, to directly determine the extent of expansion and immunodominance within the CD8+ T cell compartment following exposure to male tissue. Immunization with male bone marrow (BM), spleen, dendritic cells (DCs) and by skin graft led to rapid expansion of both specificities occupying up to >20% of the CD8+ T cell pool. At a high dose, whole BM or spleen were found to be more effective at stimulating the response than BM-derived DCs. In vivo, immunodominance within the responding cell population was only observed following chronic Ag stimulation, whereas epitope immunodominance was established rapidly following in vitro restimulation. Peptide affinity for the restricting MHC molecule was greater for the immunodominant epitope, suggesting that this might be a factor in the emergence of immunodominance. Using tetramers, we were able to directly visualize the cross-primed CD8+ HY response, but we did not find it to be the principal route for MHC class I presentation. Immunization with female spleen or DCs coated with the full complement of defined HY peptides, including the A(b)-restricted CD4+ Th cell determinant, failed to induce tetramer-reactive cells.

Immune haemolytic anaemia following T cell-depleted allogeneic bone marrow transplantation for chronic myeloid leukaemia: association with leukaemic relapse and treatment with donor lymphocyte infusions

Immune haemolytic anaemia (IHA) is a recognised complication after allogeneic stem cell transplantation (SCT) and occurs more frequently if marrow cells have been subjected to T cell depletion (TCD). Among 58 consecutive patients who underwent TCD-allogeneic SCT from volunteer unrelated donors for the treatment of CML at the Hammersmith Hospital during a 3-year period (1 March 1996 to 28 February 1999) we identified nine cases of IHA. All patients had a strongly positive direct and indirect antiglobulin test and in eight patients the serological findings were typical of warm-type haemolysis often with antibody specificities within the Rh system. All nine cases had clinically significant haemolysis and were treated initially with prednisolone and immunoglobulin. The onset of IHA coincided with the occurrence of leukaemic relapse in six cases, and the presence of host haemopoiesis confirmed by lineage-specific chimerism in all four cases studied. Five patients received donor lymphocyte infusions (DLI); in three molecular remission and the restoration of full donor chimerism coincided with resolution of haemolysis. We conclude that in the context of leukaemic relapse, DLI is an effective therapy for IHA following allografts involving TCD.

Early detection of BCR-ABL transcripts by quantitative reverse transcriptase-polymerase chain reaction predicts outcome after allogeneic stem cell transplantation for chronic myeloid leukemia

The reverse transcriptase-polymerase chain reaction (RT-PCR) has become widely used for monitoring minimal residual disease after allogeneic stem cell transplantation (SCT) for chronic myeloid leukemia (CML). However, most of these studies were performed using qualitative RT-PCR, and the interpretation of the results obtained has been conflicting. The correlation of a quantitative RT-PCR test performed early after SCT (at 3 to 5 months) and long-term outcome of CML patients surviving for more than 6 months was studied. Between January 1991 and June 1999, data from 138 CML patients who received allografts were evaluated. Early RT-PCR results were classified as (1) negative if there were no BCR-ABL transcripts detected (n = 61), (2) positive at low level if the total number of BCR-ABL transcripts was less than 100 per microg RNA and/or the BCR-ABL/ABL ratio was less than 0.02% (n = 14), or (3) positive at high level if transcript levels exceeded the thresholds defined above (n = 63). Three years after SCT the cumulative incidence of relapse was 16.7%, 42.9%, and 86.4%, respectively (P =.0001). The relationship between BCR-ABL transcript level and probability of relapse was apparent whether patients had received sibling or unrelated donor SCT and also whether or not the transplantation was T cell depleted. The results suggest that quantitative RT-PCR performed early after SCT is useful for predicting outcome and may help to define the need for further treatment.

Cytomegalovirus seropositivity adversely influences outcome after T-depleted unrelated donor transplant in patients with chronic myeloid leukaemia: the case for tailored graft-versus-host disease prophylaxis

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality after haematopoietic stem cell transplantation from matched unrelated donors (MUD). The role of T-cell depletion (TCD) as a strategy to prevent GVHD is controversial because of the associated increased risk of leukaemic relapse, graft failure and delayed immune reconstitution. The demonstration that donor lymphocyte infusion (DLI) is effective salvage therapy if patients relapse after transplantation for chronic myeloid leukaemia (CML) prompted us to examine the proposal that TCD may be a form of GVHD prophylaxis particularly suited to this disease in patients undergoing MUD transplantation. We analysed the outcome of 106 consecutive patients with CML in first chronic phase who underwent MUD transplantation. Patients were conditioned with cyclophosphamide and total body irradiation (TBI), and received in vivo TCD, using CD52 monoclonal antibody, as GVHD prophylaxis. Donor lymphocytes were infused at the time of leukaemic relapse. The projected survival at 5 years for all patients was 52.6%. The probability of developing severe acute GVHD (grade 3 or 4) was 14.5%. The only significant predictor of overall survival in univariate and multivariate analysis was patient cytomegalovirus (CMV) serostatus: in CMV-negative patients survival at 5 years was 60% vs. 42% in CMV-positive patients (P = 0.006). The use of TCD was associated with an increased risk of relapse (62% probability at 5 years after transplant), but 80% of patients who received DLI achieved molecular remission that was durable in all but two cases. In vivo TCD, in conjunction with DLI at relapse, is a valuable GVHD prophylactic regimen in CMV-seronegative recipients of MUD allografts, but in CMV-seropositive patients this approach is associated with an increased non-relapse mortality. Consequently, GVHD prophylactic regimens in MUD transplantation should be tailored according to the patient and donor pretransplant characteristics.

Durability of responses following donor lymphocyte infusions for patients who relapse after allogeneic stem cell transplantation for chronic myeloid leukemia

An analysis was performed of the response to treatment with donor lymphocyte infusions (DLI) and the survival in 66 consecutive patients who relapsed after primary treatment by allogeneic stem cell transplantation for BCR-ABL-positive chronic myeloid leukemia. The transplant donor was an HLA-identical sibling (n = 35) or a "matched" unrelated volunteer (n = 31). Fifty-seven patients were transplanted in chronic phase, eight in accelerated phase, and one in second chronic phase. The recognition of relapse was based on precise molecular, cytogenetic, or hematologic criteria. The median interval from transplant to relapse was 12 months (range 3-85). The median interval from relapse to initiation of DLI was 9.4 months (range 1-70). Patients received DLI from their original transplant donors on a bulk-dose (n = 34) or on an escalating-dose (n = 32) regimen. Patients were monitored serially by hematologic, cytogenetic, and molecular criteria. Molecular remission was defined by the finding of negative results by nested primer reverse transcriptase polymerase chain reaction (RT-PCR) for BCR-ABL transcripts on two consecutive occasions, subject to satisfactory controls. Forty-four patients (67%) achieved molecular remission. Patients who had relapsed to advanced phase disease and patients with short intervals between transplant and relapse had significantly lower probabilities of achieving molecular remission. Of the 44 patients who achieved molecular remission, 4 reverted to a PCR-positive status at 15, 18, 37, and 87 weeks after remission. The probability of survival for patients who achieved molecular remission was significantly better than for those who failed to do so (95% versus 53% at 3 years post-DLI, P = .0001). We conclude that the majority of molecular remissions after DLI are durable, and thus the majority of responding patients may prove to have been cured. (Blood. 2000;96:2712-2716)