Donor T-cell alloreactivity against host thymic epithelium limits T-cell development after bone marrow transplantation

Acute graft-versus-host disease (aGVHD) impairs thymus-dependent T-cell regeneration in recipients of allogeneic bone marrow transplants through yet to be defined mechanisms. Here, we demonstrate in mice that MHC-mismatched donor T cells home into the thymus of unconditioned recipients. There, activated donor T cells secrete IFN-gamma, which in turn stimulates the programmed cell death of thymic epithelial cells (TECs). Because TECs themselves are competent and sufficient to prime naive allospecific T cells and to elicit their effector function, the elimination of host-type professional antigen-presenting cells (APCs) does not prevent donor T-cell activation and TEC apoptosis, thus precluding normal thymopoiesis in transplant recipients. Hence, strategies that protect TECs may be necessary to improve immune reconstitution following allogeneic bone marrow transplantation.

Immune reconstitution diseases: is it possible to establish recommendations?

The introduction of combination antiretroviral therapy (cART) has attracted the attention of scientists and physicians all over the world to the phenomenon known as IRD, immune restoration disease. The management of IRD depends on the correct diagnosis of the syndrome, which can be difficult to establish. The atypical presentation and unpredictable course of the disease may require individual decisions regarding a delay of cART or its interruption as well as the use of corticosteroids. Thus the frequent need for individualized management of IRD can make it difficult to obtain enough results from prospective randomized trials to establish strict recommendations. However, they should be initiated as soon as possible.

A recombinant human IgM promotes myelin repair after a single, very low dose

A recombinant human monoclonal IgM, rHIgM22, promotes the synthesis of new myelin when used to treat several animal models of demyelination. rHIgM22 binds to myelin and the surface of oligodendrocytes and accumulates at central nervous system lesions in vivo. The minimal dose of monoclonal IgM required to promote remyelination has a direct bearing on the proposed mechanism of action. A dose ranging study using rHIgM22 was performed in mice with chronic virus-induced demyelination, a model of chronic progressive multiple sclerosis. The lowest tested dose of rHIgM22 effective at promoting spinal cord remyelination was a single 500-ng intraperitoneal bolus injection. A time course study of spinal cord repair performed in chronically demyelinated mice revealed that remyelination plateaued by 5 weeks following treatment with rHIgM22. Two doses of rHIgM22 spaced 5 weeks apart did not increase the extent of remyelination over a single dose. The half-life of rHIgM22 in the mouse systemic circulation was determined to be 15 hr; the human IgM serum concentration was close to zero by 48 hr following antibody administration. We propose that the specificity of rHIgM22 for myelin on living tissue targets the antibody to demyelinated lesions, initiating a long-term reparative effect on the central nervous system.

Successful immune reconstitution decreases leukemic relapse and improves survival in recipients of unrelated cord blood transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is established therapy for selected patients with acute leukemia. After transplantation, antileukemic immune responses are believed to eliminate residual leukemia cells and decrease the likelihood of relapse. However, the clinical effect of successful antigen-specific immune reconstitution after HSCT on the likelihood of leukemic relapse and overall survival is not known. Pediatric recipients of unrelated cord blood transplants who underwent transplantation for acute leukemia were sequentially evaluated for their development of antigen-specific T-lymphocyte immunity to herpes viruses. The clinical effect of a positive antigen-specific response on relapse-free survival was determined. The presence of an antigen-specific response resulted in a relapse-free survival advantage (P = .0001), which was primarily due to a decrease in leukemic relapse (P = .003). Proportional hazards modeling for time to relapse and time to relapse or death defined 3 variables that were strongly associated with a poor outcome: female gender, poor remission status before transplantation, and negative antigen-specific T-lymphocyte proliferation. Notably neither acute nor chronic graft-versus-host disease had any effect on the incidence of leukemic relapse. Successful antigen-specific immune reconstitution after unrelated cord blood transplantation results in decreased leukemic relapse and improved overall survival.

Interleukin-6 promotes sprouting and functional recovery in lesioned organotypic hippocampal slice cultures

Interleukin (IL)-6 is a pro-inflammatory cytokine now widely recognized to contribute to the molecular events that follow CNS injury. Little is known, however, about its action on axonal sprouting and regeneration in the brain. We addressed this issue using the model of transection of Schaffer collaterals in mice organotypic hippocampal slice cultures. Transection of slice cultures was associated with a marked release of IL-6 that could be neutralized by an IL-6 blocking antibody. We monitored functional recovery across the lesion by recording synaptic responses using a multi-electrode array. We found that application of IL-6 antibodies to the cultures after lesioning significantly reduced functional recovery across the lesion. Furthermore, the level of expression of the 43-kDa growth-associated protein (GAP-43) was lower in slices treated with the IL-6 neutralizing antibody than in those treated with a control IgG. Conversely, addition of exogenous IL-6 to the culture medium resulted in a dose-dependent enhancement of functional recovery across the lesion and a higher level of expression of GAP-43. Co-culture of CA3 hemi-slices from thy1-YFP mice with CA1 hemi-slices from wild-type animals confirmed that IL-6-treated co-cultures exhibited an increased number of growing fluorescent fibres across the lesion site. Taken together these data indicate that IL-6 plays an important role in CNS repair mechanisms by promoting regrowth and axon regeneration.

Optimizing immunotherapy in multiple myeloma: Restoring the function of patients' monocyte-derived dendritic cells by inhibiting p38 or activating MEK/ERK MAPK and neutralizing interleukin-6 in progenitor cells

Previous studies demonstrated that circulating dendritic cells (DCs) in myeloma patients were functionally abnormal. However, the phenotype and function of patients' monocyte-derived DCs (MoDCs), which are commonly used for immunotherapy, were poorly defined. This study was undertaken to examine the quality of MoDCs from myeloma patients compared with cells from healthy donors. We found that patient-derived MoDCs are phenotypically and functionally defective. Compared with their normal counterparts, patient-derived, mature MoDCs expressed significantly lower levels of CD1a, CD40, CD80, and HLA-DR and were poor at activating alloreactive T cells, presenting recall antigen, and activating autologous antigen- and myeloma-specific T cells. These abnormalities may be attributed to elevated production of autocrine cytokines such as IL-6, activated p38 and STAT3, and inhibited MEK/ERK signaling pathways in the progenitor cells. Treatment with neutralizing IL-6-specific antibody and, more importantly, p38 inhibitor, or both, could correct these abnormalities. Treating patient-derived cells with these agents not only significantly increased cell yield but also produced MoDCs that were as functional as their normal counterparts. Thus, this study has delineated the mechanistic defects of MoDCs from myeloma patients and identified ways for restoring the function of the cells to improve the efficacy of DC-based immunotherapy in this disease.

Augmented locomotor recovery after spinal cord injury in the athymic nude rat

The immune response contributes to ongoing secondary tissue destruction following spinal cord injury (SCI). Although infiltrating neutrophils and monocytes have been well studied in this process, T-cells have received less attention. The objective of this study was to assess locomotor recovery and tissue morphology after SCI in athymic (nude) rats, in which T-cell numbers are reduced. Results in athymic rats were compared with heterozygote littermates with normal T-cell profiles and with Sprague-Dawley rats from previous studies in our lab. Following transection of rat spinal cords at T10, we assessed the animals' locomotor recovery on a weekly basis for up to 11 weeks, using the Basso-Beattie-Bresnahan locomotor rating scale. Nude rats showed better locomotor recovery than did heterozygote or Sprague-Dawley rats, achieving scores of 5.6 +/- 0.8 versus 1.0 +/- 0.0, respectively (p = 0.002), at 4 weeks postinjury. The improved recovery of nude rats persisted for the 11-week postinjury assessment period, and was consistent with improved spinal reflexes rather than with recovery of descending motor pathways. Anatomical evaluation at 11 weeks indicated no difference in nude versus heterozygote rats in the size or distribution of cavities caudal to the transection site, but secondary damage was more severe rostral to the transection site in heterozygote rats. In neither group did cavities extend beyond 4 mm caudal to the transection site, and were therefore not directly responsible for the functional differences between the two groups. Cellular expression of the microglia/macrophage antigen ectodysplasin A (ED1) was reduced in nude rats as compared to heterozygotes, but no difference was observed in expression levels of 5-hydroxytryptamine, the 200-kDa neurofilament, or glial fibrillary acidic protein. The findings of the study show that a reduction in T-cell numbers significantly improves locomotor recovery after spinal cord transection, indicating a deleterious role for these immune cells in neural repair after trauma.

Myostatin inhibition slows muscle atrophy in rodent models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease leading to motor neuron cell death, but recent studies suggest that non-neuronal cells may contribute to the pathological mechanisms involved. Myostatin is a negative regulator of muscle growth whose function can be inhibited using neutralizing antibodies. In this study, we used transgenic mouse and rat models of ALS to test whether treatment with anti-myostatin antibody slows muscle atrophy, motor neuron loss, or disease onset and progression. Significant increases in muscle mass and strength were observed in myostatin-antibody-treated SOD1(G93A) mice and rats prior to disease onset and during early-stage disease. By late stage disease, only diaphragm muscle remained significantly different in treated animals in comparison to untreated controls. Myostatin inhibition did not delay disease onset nor extend survival in either the SOD1(G93A) mouse or rat. Together, these results indicate that inhibition of myostatin does not protect against the onset and progression of motor neuron degenerative disease. However, the preservation of skeletal muscle during early-stage disease and improved diaphragm morphology and function maintained through late stage disease suggest that anti-myostatin therapy may promote some improved muscle function in ALS.

Prospective simultaneous quantification of human cytomegalovirus-specific CD4+ and CD8+ T-cell reconstitution in young recipients of allogeneic hematopoietic stem cell transplants

We investigated immune reconstitution against human cytomegalovirus (HCMV) in 57 hematopoietic stem cell transplant (HSCT) recipients, aged 1 to 24 years, through a novel method combining T-cell stimulation by HCMV-infected autologous dendritic cells with simultaneous cytometric quantification of HCMV-specific, IFNgamma-producing CD4(+) and CD8(+) T cells. Lymphoproliferative response (LPR) to HCMV antigens was also determined. Patients were stratified into 2 groups according to HCMV serostatus, comprising 39 HCMV-seropositive (R(+)) and 18 HCMV-seronegative (R(-)) patients who received a transplant from a sero-positive donor. Recovery of both HCMV-specific CD4(+) and CD8(+) T-cell immunity occurred in all 39 R(+) patients within 6 months and in 6 (33%) of 18 R(-) patients within 12 months. In R(+) patients, the median numbers of HCMV-specific CD8(+) and CD4(+)T cells were significantly higher than those of healthy controls, starting from days +60 and +180, respectively. In (R-) patients, the median numbers of HCMV-specific T cells were consistently lower than in R(+) patients. LPR was delayed compared with reconstitution of IFNgamma-producing T cells. Patients with delayed specific immune reconstitution experienced recurrent episodes of HCMV infection. HCMV seropositivity of young HSCT recipients is the major factor responsible for HCMV-specific immune reconstitution, irrespective of donor serostatus, and measurement of HCMV-specific T cells appears useful for correct management of HCMV infection.

Recovery from experimental allergic encephalomyelitis is TGF-β dependent and associated with increases in CD4+LAP+ and CD4+CD25+ T cells

SJL mice are highly susceptible to proteolipid protein (PLP) 139-151-induced experimental allergic encephalomyelitis (EAE). The disease is characterized by a relapsing-remitting type of paralysis. However, the mechanism by which animals recover from EAE is poorly understood. Here, we investigated the role of regulatory T cells in the recovery from disease. We found that Forkhead box P3-expressing CD4+CD25+ T cells were increased in the blood, draining lymph node and spleen of EAE-recovered SJL mice. These cells were anergic and inhibited proliferation of CD4+CD25- T cells to PLP 139-151 or anti-CD3 antibody stimulation. Depletion of CD4+CD25+ T cells during the recovery phase exacerbated disease, resulted in the expansion of IA(s)/PLP 139-151-tetramer-positive cells and enhanced IFN-gamma production. In addition, transforming growth factor-beta (TGF-beta) was shown to be involved in the recovery from EAE as the percentage of CD4+ cells expressing TGF-beta latency-associated peptide (LAP) on the cell surface increased significantly in blood and spleen of EAE-recovered mice as compared with the naive mice and in vivo neutralization of TGF-beta abolished recovery from disease. Taken together, our results demonstrate that both CD4+CD25+ and CD4+LAP+ regulatory T cells mediate recovery from PLP 139-151-induced EAE in SJL mice in which TGF-beta plays an important role.

An open label study of the effects of rituximab in neuromyelitis optica

Eight patients with worsening neuromyelitis optica were treated with rituximab to achieve B cell depletion. Treatment was well tolerated. Six of eight patients were relapse free and median attack rate declined from 2.6 attacks/patient/year to 0 attacks/patient/year (p = 0.0078). Seven of eight patients experienced substantial recovery of neurologic function over 1 year of average follow-up. The pretreatment median Expanded Disability Status Scale score was 7.5, and at follow-up examination was 5.5 (p = 0.013).

Cytomegalovirus (CMV) infections and CMV-specific cellular immune reconstitution following reduced intensity conditioning allogeneic stem cell transplantation with Alemtuzumab

We studied the incidence and recurrence of Cytomegalovirus (CMV) infection and reactivation in 38 recipients of Alemtuzumab reduced intensity conditioning-stem cell transplantation, and used CMV-HLA tetramer studies to discover if these events correlated with recovery of circulating CMV-specific CD8+ T cells (cytotoxic T lymphocyte (CTLs)). The cumulative incidence of CMV infection was 60% at 1 year (95% CI, 45-78%) with a median reactivation time of 24 days (range 5-95 days). All patients with CMV reactivation received Ganciclovir or Foscarnet, and only one developed CMV disease. More strikingly, only 8/21 patients had relapse of CMV antigenemia. Tetramer analysis in 13 patients showed that 11 reconstituted CMV CTLs (7/11 by day 30 and 10/11 by day 90). The development of CMV infection was accompanied by a >5-fold rise of CMV CTLs. Recurrence of CMV infection occurred only in the patients who failed to generate a CTL response to the virus. Hence, recipients of SCT using Alemtuzumab-RIC are initially profoundly immunosuppressed and have a high incidence of early CMV reactivation. However, in the majority of patients, infection is transient, and antiviral T cell reconstitution is rapid. Monitoring with CMV-specific CTLs may help identify the subset of patients at risk from recurrent infection or disease.

Comparative evaluation of gastrointestinal transit and immune response between laparoscopic and open gastrectomy in a porcine model

Several reports have shown advantages of laparoscopic gastrointestinal (GI) procedures when compared with their open counterparts. The aim of this study was to assess the differences of GI transit and immune response between laparoscopic and open gastrectomy in a porcine model. Fourteen pigs were assigned to undergo partial gastrectomy, either by laparoscopy (lap group) or by laparotomy (open group). GI transit was assessed using 24 markers and measured until half of markers were evacuated. To assess immune response, we used delayed-type hypersensitivity skin antigen testing (DTH) with vaccine antigen. DTH was evaluated at 48 hours after the primary injection for induration. After 2 weeks, all animals underwent necropsy and were evaluated for adhesion formation using a scoring scale. Operation time was significantly longer in the lap group. The GI transit in the postoperative phase was significantly prolonged compared with the preoperative measured times. Postoperatively, the GI transit in the open group was significantly prolonged compared with the lap group. Immune response measured by DTH was better preserved in the lap group than in the open group. Adhesion formation was significantly less in the lap group. We concluded that laparoscopic gastrectomy resulted in faster bowel recovery and less immune suppression.

Adrenal function improves in asthmatic children on inhaled steroids: a longitudinal study

BACKGROUND/AIMS

Asthmatic children on long-term treatment with inhaled corticosteroids (ICS) may exhibit mild adrenal suppression. We aimed to test the hypothesis that baseline adrenal function of some asthmatic children might be lower than that of others and that this difference might be accentuated by ICS therapy.

METHODS

A low-dose Synacthen test was performed in 41 prepubertal asthmatic children placed on long-term inhaled budesonide (400 microg/day) prior to the onset of ICS treatment, 6 and 12 months later. Five children withdrew before the 6- and another 2 before the 12-month follow-up.

RESULTS

Low adrenal function was demonstrated in 4 children (9.8%) upon recruitment and in another 8 at the 6-month evaluation (22.2%). Adrenal function normalized in the aforementioned 4 children at the 6-month evaluation, while 6 (17.6%) exhibited suppressed adrenal function at the 12-month evaluation. Three of these patients had also exhibited adrenal suppression at the 6-month visit. A significant improvement in peak cortisol values from baseline to the 6- and 12-month evaluation (95% confidence intervals: -283.9 to -69.0 and -239.8 to -50.8, respectively) was evident when children with suppressed adrenal response at the second or third evaluation were excluded.

CONCLUSIONS

In many asthmatic children, adrenal response improves on long-term ICS. The expected adrenal suppression of certain patients on maintenance ICS appears to constitute a separate phenomenon.

Reconstitution of adaptive and innate immunity following allogeneic hematopoietic stem cell transplantation in humans

Allogeneic hematopoietic stem cell transplantation is a potentially curative treatment modality for a number of hematologic malignancies, as well as inherited immunodeficiencies and hemoglobinopathies, and may also have a role in selected acquired autoimmune disorders. The complete or near-complete ablation of host immunity and subsequent establishment of donor-derived immunity that is required for successful engraftment and long-term outcomes provide a major obstacle to such transplantation approaches. A delicate balance exists between the need for the reconstituted donor-derived immunity to provide both protection against pathogenic challenges and graft-versus-malignancy activity, and the potentially harmful expansion of alloreactive T-cell clones mediating GvHD. The search for interventions that would allow more rapid and selective reconstitution of beneficial immune specificities continues to be informed by the development of new tools enabling a more precise dissection of the kinetics of reconstituting populations. This review summarizes more recent data on immune reconstitution following allogeneic transplantation in humans.

Recent thymic output function in patients with hematological malignancy

Thymic function is important for the generation of T-cell diversity in the periphery of both children and adults during both health and disease. Until recently, thymic function could not be monitored, as a consequence of the absence of adequate technology to differentiate recent thymic emigrants (RTEs) from naïve T cells. The generation of TCR diversity occurs in the thymus through recombination of gene segments encoding the variable parts of the TCR alpha and beta chains. During these processes, by-products of the rearrangements are generated in the form of signal joint T-cell receptor excision circles (sjTRECs). As sjTRECs are stable extrachromosomal DNA fragments, they are not replicated during mitosis and thus diluted with each round of cell division, and are therefore most frequent in naïve T cells that have recently left the thymus, their quantification is actually considered as a valuable tool to estimate thymic function. Therefore, quantitative sjTRECs content have been recently used to assess thymic output during both health and disease. In this review, we summarize recent data on the recent thymic output function feature in patients with hematological malignancy and the immune reconstitution after stem cell transplantation and we also characterize factors that may improve the thymic output function.

Correction of canine X-linked severe combined immunodeficiency by in vivo retroviral gene therapy

X-linked severe combined immunodeficiency (XSCID) is characterized by profound immunodeficiency and early mortality, the only potential cure being hematopoietic stem cell (HSC) transplantation or gene therapy. Current clinical gene therapy protocols targeting HSCs are based upon ex vivo gene transfer, potentially limited by the adequacy of HSC harvest, transduction efficiencies of repopulating HSCs, and the potential loss of their engraftment potential during ex vivo culture. We demonstrate an important proof of principle by showing achievement of durable immune reconstitution in XSCID dogs following intravenous injection of concentrated RD114-pseudotyped retrovirus vector encoding the corrective gene, the interleukin-2 receptor gamma chain (gamma c). In 3 of 4 dogs treated, normalization of numbers and function of T cells were observed. Two long-term-surviving animals (16 and 18 months) showed significant marking of B lymphocytes and myeloid cells, normalization of IgG levels, and protective humoral immune response to immunization. There were no adverse effects from in vivo gene therapy, and in one dog that reached sexual maturity, sparing of gonadal tissue from gene transfer was demonstrated. This is the first demonstration that in vivo gene therapy targeting HSCs can restore both cellular and humoral immunity in a large-animal model of a fatal immunodeficiency.

Expansion of CD1d-restricted NKT cells in patients with primary HIV-1 infection treated with interleukin-2

Innate CD1d-restricted natural killer T (NKT) cells are infected and lost in HIV-1-infected patients, and this could contribute to HIV-1 pathogenesis because NKT cells play an important role in directing both adaptive and innate immunity. Administration of interleukin-2 (IL-2) to HIV-1-infected patients leads to substantial and sustained CD4+ T-cell expansion, involving both naive and memory cells. We investigated whether IL-2 treatment could restore the NKT cell compartment in patients with primary HIV-1 infection. We show that IL-2 combined with effective antiretroviral therapy (ART) resulted in significant expansion of CD1d-restricted NKT cells. Expansion occurred in both the CD4- and CD4+ subsets of NKT cells, and expanded cells expressed the CD161 maturation marker while expression of the HIV coreceptor CCR5 was reduced. These data indicate that IL-2 treatment in combination with effective ART is beneficial for the restoration of innate NKT cell immunity in patients with primary HIV-1 infection.

Reduced-intensity conditioning regimen preserves thymic function in the early period after hematopoietic stem cell transplantation

OBJECTIVE

To compare T-cell reconstitution in two groups of patients submitted to allogeneic stem cell transplantation (SCT): those receiving reduced-intensity conditioning (RIC, n = 24) and those receiving myeloablative conditioning (MA, n = 27).

METHODS

Fifty-one consecutive patients undergoing SCT were evaluated. Serial assessments of lymphocyte subsets and T cell receptor excision circles (TRECs) levels were performed using multiparametric flow cytometry and real-time PCR, respectively.

RESULTS

During the first 6 months posttransplant, total and naïve CD4(+) T cell counts were higher after RIC-SCT than after MA-SCT (total CD4(+): p = 0.04, p = 0.08, and p = 0.058; naïve CD4(+): p = 0.14, p = 0.05, and p = 0.01 at 1, 3, and 6 months, respectively). In both groups of patients, TRECs levels were low or undetectable in the first 3 months after SCT and progressively increased during the study. However, a higher proportion of patients with detectable levels of TRECs was observed in RIC-SCT at 1 and 3 months and more patients in this group reached normal levels of TRECs at 6 months post-SCT. In the multivariate analysis, including factors such as type of donor (sibling vs unrelated), dose of CD34(+) cells infused with the graft, patient age, and graft-vs-host disease (GVHD), the most important factor influencing TRECs recovery in the early period after SCT was the type of conditioning regimen.

CONCLUSIONS

In this study, the pattern of immune reconstitution after RIC-SCT was different from that of MA-SCT and was characterized by higher posttransplant naïve CD4(+) T cell counts and TRECs levels in the early period after transplant.

T-Cell Immune Reconstitution after Hematopoietic Stem Cell Transplantation for HIV-Associated Lymphoma

BACKGROUND

One of the major concern for high-dose chemotherapy and hematopoietic stem cell transplantation (HSCT) for HIV-associated lymphoma is that posttransplant immunosuppression might worsen immune defects of HIV individuals. Since the introduction of highly active antiretroviral therapy has made HSCT possible also in these patients, we analyzed whether the immune system already compromised by HIV infection might support an efficient T-cell recovery after HSCT.

METHODS

The kinetics and the extent of T-cell reconstitution were investigated before and after HSCT in four patients with HIV-related lymphoma (one with Hodgkin's Disease and three with non-Hodgkin's lymphoma) by measuring the thymic output, the level of IL-7 and the heterogeneity of T-cell repertoire. T-cell competence was gauged at two functional levels: by determining the number of T-cell divisions and by measuring IFN-gamma production.

RESULTS

The thymus of transplanted patients can be capable of generating new T cells, but there is no relationship between increasing number of newly produced lymphocytes and modification of IL-7 level. Various T-cell subsets, expressing different T-cell receptor variable beta genes, were preferentially expanded in CD8 population and most of them showed a restricted diversity. Furthermore, CD3 lymphocytes showed heterogeneous behaviors in terms of proliferative capability and IFN-gamma production.

CONCLUSIONS

High-dose therapy and HSCT in HIV patients under highly active antiretroviral therapy does not worsen the immune defects. On the contrary, in the presence of some conditions (including the type of hematologic malignancy, the therapy compliance, and the immune status before transplantation), high-dose therapy and HSCT might support the improvement of immune conditions.

Intrathymic administration of hematopoietic progenitor cells enhances T cell reconstitution in ZAP-70 severe combined immunodeficiency

Patients with severe combined immunodeficiency (SCID) present with opportunistic infections that are almost universally fatal in infancy. The mainstay treatment for these patients is allogeneic hematopoietic stem cell (HSC) transplantation, but sustained polyclonal T cell reconstitution is too often unsatisfactory. Although transplantation is conventionally performed by i.v. administration of HSC, we hypothesized that an intrathymic strategy would be superior. Indeed, several progenitor cell populations are incapable of homing to the thymus, the major site of T cell differentiation, and it appears that there are extensive time periods during which the thymus is refractory to progenitor cell import. To test this hypothesis, nonconditioned infant ZAP-70-deficient SCID mice were intrathymically injected with WT bone marrow progenitor cells, a procedure accomplished without surgical intervention. Upon intrathymic HSC injection, there was a more rapid T cell differentiation, with mature thymocytes detected by 4 weeks after transplantation. Intrathymic injection of HSC also resulted in significantly higher numbers of peripheral T cells, increased percentages of naïve T cells, and more diverse T cell receptor repertoires. Moreover, T cell reconstitution after intrathymic transplantation was obtained after injection of 10-fold fewer donor HSC. Thus, this intrathymic transplantation approach may improve the outcome of SCID patients by enhancing T cell reconstitution.

Establishing a platform for immunotherapy: clinical outcome and study of immune reconstitution after high-dose chemotherapy with progenitor cell support in breast cancer patients

Tumor vaccine after high-dose chemotherapy (HDC) and autologous stem cell transplantation (ASCT) aims at directing immune recovery toward tumor responses after optimizing minimal residual disease. We have characterized T-cell recovery and tumor response after a regimen devised as a platform for such immunotherapy. One hundred patients with high-risk or metastatic breast cancer received 3 to 7 cycles of paclitaxel and cyclophosphamide (overall response rate, 78%) and then HDC with melphalan and etoposide. Seventy-one patients received HDC and ASCT (no mortality at 100 days). At 24 months after transplantation, progression-free and overall survival probabilities for patients with stage IIIA, IIIB, and IV disease were 82%, 81%, and 42% and 100%, 94%, and 68%, respectively. The median progression-free and overall survivals from entry on study for stage IV patients were 15.3 and 38.1 months, respectively. CD3 + , CD8 + , and CD4 + cells were severely depleted after ASCT. Although total CD8 + T-cell numbers approached the normal range by 3 months, most of these cells were CD28 - . Naive CD45RA + CD4 + T cells approached the normal range only 18 months after ASCT and only in younger patients. The described observations provide the basis for devising a strategy for cancer vaccine administration after ASCT. Incorporating immune reconstitution enhancement after ASCT may be advantageous.

Peripheral T-cell expansion and low infection rate after reduced-intensity conditioning and allogeneic blood stem cell transplantation

Peripheral blood stem cell transplantation after reduced-intensity conditioning (RIC-PBSCT) regimen is an alternative to conventional regimens with less immediate toxicity. Since immune recovery is of crucial importance for the control of infections, we retrospectively studied the recovery of T-, B- and NK cell subsets in 20 consecutive patients undergoing RIC-PBSCT. We also studied the thymic output using T-cell receptor excision circle assay. Engraftment was rapid and few infectious complications were seen: three early (before 2.5 months) cases of asymptomatic cytomegalovirus reactivation, two late Gram-negative bacterial infections and no fungal infection. While CD4+ T-cell reconstitution was slow, CD8+ T-cell counts were close to normal values at 4 months. Median CD19+ B-cell counts reached normal values at 11 months. Rapid CD56+ NK cell reconstitution was noticed as early as 1.5 months. Low T-cell receptor excision circle numbers and preponderance of memory-type subsets among T cells further suggested that CD8+ T-cell reconstitution resulted predominantly from peripheral expansion and that thymic-dependent reconstitution was severely impaired. In conclusion, large peripheral T-cell expansion may compensate for late thymic-dependent lymphopoiesis, and may, with other factors such as NK and B-cell reconstitution and careful antiinfectious prophylaxis, help limit the incidence of severe infections after RIC-PBSCT.

Numbers of -expressing CD4CD25 T cells do not correlate with the establishment of long-term tolerance after allogeneic stem cell transplantation

OBJECTIVE

Regulatory CD4 T cells that express high levels of CD25 play a vital role in the maintenance of tolerance to self antigens and are required for the induction of nonresponsiveness to alloantigens. The long-term CD4+CD25high T-cell reconstitution after allogeneic stem cell transplantation is unknown. Here, we evaluated whether recovery of this T-cell subset might be linked to the establishment of full donor/recipient tolerance.

METHODS

The frequency of CD4+CD25high T cells was determined by Fluorescence Activated Cell Sorter (FACS) analysis in 31 patients, with a mean follow-up of more than 31 months posttransplant. The expression levels of Foxp3 mRNA were assessed by quantitative real-time polymerase chain reaction (RT-PCR).

RESULTS

Patients with or without graft-versus-host disease (GvHD) had significant and persistent CD4 T-cell lymphopenia. The relative frequency of CD25high cells and the expression levels of FoxP3 mRNA within this subset were similar between all patients and healthy controls. No significant difference was found in the number of Foxp3-expressing CD4+CD25high T cells in patients with or without GvHD. Finally, younger age and absence of previous GvHD were significantly linked to CD4+CD25high T-cell recovery.

CONCLUSION

The low number of Foxp3-expressing CD4+CD25high T cells in grafted patients is not a specific default of this compartment but a consequence of global CD4 T-cell lymphopenia after allogeneic stem cell transplantation. Moreover, levels of Foxp3 mRNA in the CD25+ T-cell compartment do not allow predicting the development of GvHD in the long term.

Reduced-intensity conditioning containing low-dose alemtuzumab before allogeneic peripheral blood stem cell transplantation: graft-versus-host disease is decreased but T-cell reconstitution is delayed

OBJECTIVE

In vivo administration of alemtuzumab (an anti-CD52 antibody) is effective to decrease the incidence of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-SCT). However, posttransplant immune reconstitution is impaired, increasing the infection risk. We investigated the effect of in vivo administration of a low-dose alemtuzumab on GVHD prevention and kinetics of immune reconstitution.

PATIENTS AND METHODS

Twenty-seven patients entered a pilot study employing reduced-intensity conditioning and low-dose alemtuzumab (15 or 7.5 mg/m2) before peripheral blood allo-SCT from human leukocyte antigen-identical or one antigen-mismatched sibling donors. All lymphoid subsets were longitudinally studied at 1-3, 6, 9, 12 months after transplantation. T-cell receptor (TCR) spectratyping and T-cell receptor excision circles (TRECs) were also analyzed at various time points after allo-SCT.

RESULTS

All patients but one were engrafted. The probability of nonrelapse mortality at 100 days and 1 year were 7 and 11%, respectively; the overall survival at 2 years was 77%. The cumulative incidence of grade II-IV acute GVHD at day 100 was 11%. The overall incidence of chronic GVHD was 28%. The median time to achieve more than 200 CD4+/microL and 500 CD8+/microL were 6 and 9 months, respectively. Natural killer cells remained between the value of 300/microL and 500/microL throughout the period of follow-up whereas the median time to reach CD19+ blood concentrations of >200 cells/microL was 9 months. The normalization of TCR repertoire and increase of TREC counts began at 6 months after allo-SCT.

CONCLUSION

We have shown that low-dose alemtuzumab is effective for GVHD prevention, but its use still impairs the immune reconstitution.

Adoptive transfer of macrophages ameliorates renal fibrosis in mice

We performed adoptive transfer of bone marrow-derived (BM) macrophages following pharmacological depletion of leukocytes in a mouse model of unilateral ureteral obstruction (UUO). Treatment with cyclophosphamide (CPM) caused marked decrease in the numbers of F4/80-positive interstitial macrophages as well as in peripheral blood leukocyte counts, and adoptive transfer of BM macrophages to CPM-treated mice resulted in significant increase in the numbers of interstitial macrophages both at day 5 and at day 14 after UUO. At day 5 after UUO, no significant change was observed in the degree of renal interstitial fibrosis either by treatment with CPM or with CPM+macrophage. However, at day 14 after UUO, treatment with CPM caused significant increase in the degree of interstitial fibrosis, and adoptive macrophage transfer to these mice attenuated this enhancement in renal fibrosis. Our result suggests the role of infiltrating macrophages on facilitating tissue repair at late stage of UUO.

Persistence of lung inflammation and lung cytokines with high-resolution CT abnormalities during recovery from SARS

Background

During the acute phase of severe acute respiratory syndrome (SARS), mononuclear cells infiltration, alveolar cell desquamation and hyaline membrane formation have been described, together with dysregulation of plasma cytokine levels. Persistent high-resolution computed tomography (HRCT) abnormalities occur in SARS patients up to 40 days after recovery.

Methods

To determine further the time course of recovery of lung inflammation, we investigated the HRCT and inflammatory profiles, and coronavirus persistence in bronchoalveolar lavage fluid (BALF) of 12 patients at recovery at 60 and 90 days.

Results

At 60 days, compared to normal controls, SARS patients had increased cellularity of BALF with increased alveolar macrophages (AM) and CD8 cells. HRCT scores were increased and correlated with T-cell numbers and their subpopulations, and inversely with CD4/CD8 ratio. TNF-α, IL-6, IL-8, RANTES and MCP-1 levels were increased. Viral particles in AM were detected by electron microscopy in 7 of 12 SARS patients with high HRCT score. On day 90, HRCT scores improved significantly in 10 of 12 patients, with normalization of BALF cell counts in 6 of 12 patients with repeat bronchoscopy. Pulse steroid therapy and prolonged fever were two independent factors associated with delayed resolution of pneumonitis, in this non-randomized, retrospective analysis.

Conclusion

Resolution of pneumonitis is delayed in some patients during SARS recovery and may be associated with delayed clearance of coronavirus, Complete resolution may occur by 90 days or later.

[Immune reconstitution syndromes secondary to effective antiretroviral therapy]

Highly active antiretroviral therapy (HAART) can improve immune system function through suppression of HIV-1 replication. In some cases, a vigorous paradoxical immune response may develop. Individuals treated effectively can, because of low immune reactivity, suffer from diseases which run subclinically until HAART is introduced. These symptoms are termed IRS (immune reconstitution syndrome/immune recovery syndrome), IRD (immune restoration disease), and IRIS (immune restoration inflammatory syndrome). There are some predisposing factors, such as long-lasting HIV-1 infection, severe immunodeficiency, rapid immune restoration, immune dysregulation during immune reconstitution, subclinical infection, and genetic susceptibility. A common feature of IRS is clinical symptoms different from those observed usually in HIV-1-infected patients. Sarcoidosis and some autoimmune diseases are less common. They are present for the first time or as an exacerbation of established diseases. Diagnosis is difficult. It is very often impossible to identify the pathogen. The clinical symptoms in patients receiving HAART should be differentiated into IRS, ineffective HAART leading to the development of opportunistic infection, and drug toxicity.

Elimination of alloreactive T cells using photodynamic therapy

GvHD, the most important cause of morbidity and mortality after allogeneic stem cell transplantation, depends primarily on the ability of a donor T-cell subset to react to immunogenic host Ag. Recently developed culture conditions and treatment strategies may bring us closer to the selective elimination of such alloreactive T cells, often considered the holy grail of transplantation. Among the various therapeutic modalities, photodynamic therapy (PDT) offers a biological and global approach to the eradication of unwanted allo-activated T cells by combining mitochondrial targeting, P-glycoprotein inhibition and reactive oxygen species production. Indeed, the high potency of PDT against malignant cells has been harnessed to exert selective and extensive elimination of alloreactive T-cell subsets mediating GvHD, while preserving resting T cells with the ability to reconstitute the immune system for GvL activity and prevent or suppress viruses and fungi. The present paper reviews the basis of the PDT strategy, and the methodology employed. In vitro and in vivo studies that formed the proof of principle as a basis for human studies to investigate the clinical potential of PDT in the context of GvHD will be presented together with insights into future clinical applications of this versatile treatment platform.

Add-back of allodepleted donor T cells to improve immune reconstitution after haplo-identical stem cell transplantation

Poor immune reconstitution after haplo-identical stem cell transplantation results in high mortality from viral infections and relapse. One approach to overcome this problem is to deplete alloreactive cells selectively by deleting T cells activated by recipient stimulators, using an immunotoxin directed against the activation marker CD25. However, the degree of depletion of alloreactive cells is variable following stimulation with recipient PBMC, and this can result in GvHD. We have shown that using recipient EBV-transformed LCL as stimulators to activate donor alloreactive T cells results in more consistent depletion of in vitro alloreactivity while preserving T-cell responses to viral and potential myeloid tumor Ag. Based on these data, we have embarked on a phase I clinical dose escalation study of add-back of allo-LCL-depleted donor T cells in the haplo-identical setting, to determine if the allodepletion we achieve to allow infusion of sufficient T cells to restore useful antiviral/anti-leukemic responses without causing GvHD. Fifteen patients have so far been treated. The incidence of significant acute or chronic GvHD has been low (2/15), as has mortality from infection (1/15). Preliminary data show accelerated immune reconstitution in dose level 2 patients. Infused allodepleted donor T cells appear able to expand significantly in the face of viral reactivations, and doses as low as 3 x 10(5)/kg may be sufficient to confer useful antiviral immunity in this setting. At a median follow-up of 19.5 months, nine of 15 patients are alive and disease-free. Five patients have relapsed, all of whom have died.

Selective elimination of alloreactivity from immunotherapeutic T cells by photodynamic cell purging and memory T-cell sorting

Allogeneic stem cell transplantation (alloSCT), especially in the mismatched setting, carries a high risk of life-threatening GvHD because of activation of donor T cells by Ag present on host cells. Removal of mature donor T cells can prevent GvHD but leads to delayed immune reconstitution, and an increased incidence of opportunistic infections and disease relapse. These findings demonstrate the vital role of donor T cells in providing graft-versus-tumor (GvT) and anti-pathogen effects as well as facilitating immune reconstitution. It has been well documented that GvHD can be separated from GvT effects, making it possible potentially to eliminate GvHD while preserving the immunotherapeutic benefits of donor T cells. Over the past decade, major attempts have been made to reduce GvHD incidence without loss of GvT effect, especially in the haplo-identical setting. Novel techniques to deplete host-reactive donor T cells selectively have been explored. This review focuses on the use of the photodynamic cell purging (PDP) process and of sorting memory T cells for the selective elimination of alloreactivity. Minimizing the threat of GvHD while maximizing the beneficial GvT effect would broaden the scope and effectiveness of alloSCT.

Neuropathy resembling CIDP in patients receiving tumor necrosis factor- blockers

Tumor necrosis factor-alpha (TauNuFalpha) blockers are effective in the treatment of inflammatory arthritis but can induce autoimmune disorders including multiple sclerosis. Described are two patients who developed chronic inflammatory demyelinating polyneuropathy after initiation of anti-TNFalpha treatment.

Immune restoration following hematopoietic stem cell transplantation: an evolving target

Hematopoietic stem cell transplantation (HSCT) is the definitive cure for many malignant and nonmalignant diseases. However, delays in immune reconstitution (IR) following HSCT significantly limit the success of transplantation and increase the risk for infection and disease relapse in the transplant recipient. Therefore, ways to measure and to manipulate immune recovery following HSCT are emerging and their success depends directly upon an enhanced understanding for the underlying mechanisms responsible for reconstituted immunity and hematopoiesis. Recent discoveries in the activation, function, and regulation of dendritic cell (DC), natural killer (NK) cell, and T-lymphocyte subtypes have been critical in developing immunotherapies used to prevent graft-versus-host disease and to enhance graft-versus-leukemia. For example, regulatory T cells that induce tolerance and NK receptor-tumor ligand disparities that result in tumor lysis are being used to minimize GVHD and tumor burden, respectively. Furthermore, expansion and modulation of immune effector cells are being used to augment hematopoietic and immune recovery and to decrease transplant-related toxicity in the transplant recipient. Specifically, DC expansion and incorporation into antitumor and anti-microbial vaccines is fast approaching application into clinical trials. This paper will review our current understanding for IR following HSCT and the novel ways in which to restore immune function and decrease transplant-related toxicity in the transplant recipient.

Recovery of Valpha24+ NKT cells after hematopoietic stem cell transplantation

Human Valpha24+ natural killer T (NKT) cells have an invariant T-cell receptor-alpha chain and are activated in a CD1d-restricted manner. Valpha24+ NKT cells are thought to regulate immune responses and to play important roles in the induction of allograft tolerance. In this report, we analyzed the recovery of Valpha24+ NKT cells after hematopoietic stem cell transplantation and its correlation with graft-versus-host disease (GVHD). Patients who received a dose-reduced conditioning regimen, antithymocyte globulin- or CAMPATH-1H-containing conditioning regimen were excluded. NKT cells were reconstituted within 1 month after transplantation in peripheral blood stem cell transplantation recipients, while their numbers remained low for more than 1 year in bone marrow transplantation (BMT) recipients. The number of Valpha24+ NKT cells in BMT recipients with acute GVHD was lower than that in patients without acute GVHD, and both the CD4+ and CD4- Valpha24+ NKT subsets were significantly reduced. With regard to chronic GVHD, BMT recipients with extensive GVHD had significantly fewer Valpha24+ NKT cells than other patients. Furthermore, the number of CD4+ Valpha24+ NKT cells was also significantly reduced in patients with chronic extensive GVHD. Our results raise the possibility that the number of Valpha24+ NKT cells could be related to the development of GVHD.

Sex differences in the myocardial inflammatory response to ischemia-reperfusion injury

The myocardium generates inflammatory mediators during ischemia-reperfusion (I/R), and these mediators contribute to cardiac functional depression and apoptosis. The great majority of these data have been derived from male animals and humans. Sex has a profound effect over many inflammatory responses; however, it is unknown whether sex affects the cardiac inflammatory response to acute myocardial I/R. We hypothesized the existence of inherent sex differences in myocardial function, expression of inflammatory cytokines, and activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway after I/R. Isolated rat hearts from age-matched adult males and females were perfused (Langendorff), and myocardial contractile function was continuously recorded. After I/R, myocardium was assessed for expression of TNF-alpha, IL-1beta, and IL-6 (RT-PCR, ELISA); IL-1alpha and IL-10 mRNA (RT-PCR); and activation of p38 MAPK (Western blot). All indexes of postischemic myocardial function [left ventricular developed pressure, left ventricular end-diastolic pressure, and maximal positive (+dP/dt) and negative (-dP/dt) values of the first derivative of pressure] were significantly improved in females compared with males. Compared with males, females had decreased myocardial TNF-alpha, IL-1beta, and IL-6 (mRNA, protein) and decreased activation of p38 MAPK pathway. These data demonstrate that hearts from age-matched adult females are relatively protected against I/R injury, possibly due to a diminished inflammatory response.

Improved survival after unrelated donor bone marrow transplantation in children with primary immunodeficiency using a reduced-intensity conditioning regimen

The optimal approach to stem cell transplantation in children with immunodeficiency who lack a matched family donor is controversial. Unrelated donor stem cell transplantation gives equivalent outcome to mismatched family donor stem cell transplantation in severe combined immunodeficiency, whereas unrelated donors may be preferable in non–severe combined immunodeficiency children. However, unrelated donor stem cell transplantation with conventional conditioning regimens has been associated with significant treatment-related toxicity, particularly in non–severe combined immunodeficiency patients with preexisting organ dysfunction. We report the outcome of a series of 33 consecutive unrelated donor transplantations performed at our center in children with primary immunodeficiency using a reduced-intensity conditioning regimen between 1998 and 2001. We have compared these outcomes with a retrospective control cohort of 19 patients who underwent transplantation with myeloablative conditioning between 1994 and 1998. All children in both groups had primary engraftment. There was no statistical difference in the speed of immune reconstitution or incidence of graft-versus-host disease between the 2 groups. Overall survival was significantly better in the reduced-intensity conditioning group: 31 (94%) of 33 patients survived, compared with 10 (53%) of 19 in the myeloablative conditioning group (P = .014). We conclude that the reduced-intensity conditioning regimen results in improved survival and reduced transplantation-related mortality compared with myeloablative conditioning in high-risk patients undergoing unrelated donor transplantation.

Prediction of T-cell reconstitution by assessment of T-cell receptor excision circle before allogeneic hematopoietic stem cell transplantation in pediatric patients

The extent and rapidity with which T cells are regenerated from graft-derived precursor cells directly influences the incidence of infection and the T-cell–based graft-versus-tumor effect. Measurement of T-cell receptor excision circles (TRECs) in peripheral blood is a means of quantifying recent thymic T-cell production and has been used after transplantation in many studies to estimate thymus-dependent T-cell reconstitution. We hypothesized that the quality of thymic function before transplantation affects thymus-dependent T-cell reconstitution after transplantation. We used real-time polymerase chain reaction (PCR) to quantify signal-joint TRECs (sjTRECs) before and after transplantation. T-cell reconstitution was evaluated by T-cell receptor β (TCRβ) CDR3 size spectratyping. We tested 77 healthy sibling donors and 244 samples from 26 pediatric recipients of allogeneic hematopoietic stem cell transplantation (AHSCT). Blood from the healthy donors contained 1200 to 155 000 sjTREC copies/mL blood. Patients who had greater than 1200 copies/mL blood before transplantation showed early recovery of sjTREC numbers and TCRβ repertoire diversity. In contrast, patients who had fewer than 1200 copies/mL blood before transplantation demonstrated significantly slower restoration of thymus-dependent T cells. We conclude that the rate of reconstitution of thymus-dependent T cells is dependent on the competence of thymic function in the recipients before transplantation. Therefore, pretransplantation measurement of sjTREC may provide an important tool for predicting thymus-dependent T-cell reconstitution after transplantation.

Role of the immune system in the maintenance of mouse facial motoneuron viability after nerve injury

In the field of neuroimmunology, an emerging area of research involves the role that the immune system plays in neural injury and repair. Such immune:neural interactions may involve both neuroprotective and neurodestruction actions. To begin to address the compelling, and clinically relevant, issue of how the immune system impacts neural reparative processes, we combined the well described facial nerve injury paradigm, a simple neural injury model, with various immunodeficient mouse models, in order to delineate the contributing immune cells/factors involved in neural injury and repair. We have discovered a role for the CD4+ T cell in mediating facial motoneuron survival after facial nerve injury in the mouse. In this review, we present an overview of our work to date in this field and discuss future directions relevant to understanding key elements in the crosstalk between the immune:neural systems that develops subsequent to injury and/or trauma.

Acute dysautonomia: complete recovery after two courses of IVIg

An 11-year-old boy presented with acute dysautonomia manifesting as severe orthostatic hypotension following fever. Serial orthostatic tests with measurement of the coefficient of variation in the R-R intervals showed improvement after one course and complete recovery after two courses of intravenous high-dose immunoglobulin therapy (IVIg). Repeated courses of IVIg should be considered to treat this disorder if spontaneous remission does not occur.

Neutrophils contribute to muscle injury and impair its resolution after lengthening contractions in mice

We tested the hypotheses that: (1) neutrophil accumulation after contraction-induced muscle injury is dependent on the beta(2) integrin CD18, (2) neutrophils contribute to muscle injury and oxidative damage after contraction-induced muscle injury, and (3) neutrophils aid the resolution of contraction-induced muscle injury. These hypotheses were tested by exposing extensor digitorum longus (EDL) muscles of mice deficient in CD18 (CD18(-/-); Itgb2(tm1Bay)) and of wild type mice (C57BL/6) to in situ lengthening contractions and by quantifying markers of muscle inflammation, injury, oxidative damage and regeneration/repair. Neutrophil concentrations were significantly elevated in wild type mice at 6 h and 3 days post-lengthening contractions; however, neutrophils remained at control levels at these time points in CD18-/- mice. These data indicate that CD18 is required for neutrophil accumulation after contraction-induced muscle injury. Histological and functional (isometric force deficit) signs of muscle injury and total carbonyl content, a marker of oxidative damage, were significantly higher in wild type relative to CD18-/- mice 3 days after lengthening contractions. These data show that neutrophils exacerbate contraction-induced muscle injury. After statistically controlling for differences in the force deficit at 3 days, wild type mice also demonstrated a higher force deficit at 7 days, a lower percentage of myofibres expressing embryonic myosin heavy chain at 3 and 7 days, and a smaller cross sectional area of central nucleated myofibres at 14 days relative to CD18-/- mice. These observations suggest that neutrophils impair the restoration of muscle structure and function after injury. In conclusion, neutrophil accumulation after contraction-induced muscle injury is dependent on CD18. Furthermore, neutrophils appear to contribute to muscle injury and impair some of the events associated with the resolution of contraction-induced muscle injury.

De novo generation of CD4 T cells against viruses present in the host during immune reconstitution

T cells recognizing self-peptides are typically deleted in the thymus by negative selection. It is not known whether T cells against persistent viruses (eg, herpesviruses) are generated by the thymus (de novo) after the onset of the infection. Peptides from such viruses might be considered by the thymus as self-peptides, and T cells specific for these peptides might be deleted (negatively selected). Here we demonstrate in baboons infected with baboon cytomegalovirus and baboon lymphocryptovirus (Epstein-Barr virus-like virus) that after autologous transplantation of yellow fluorescent protein (YFP)-marked hematopoietic cells, YFP+ CD4 T cells against these viruses were generated de novo. Thus the thymus generates CD4 T cells against not only pathogens absent from the host but also pathogens present in the host. This finding provides a strong rationale to improve thymopoiesis in recipients of hematopoietic cell transplants and, perhaps, in other persons lacking de novo-generated CD4 T cells, such as AIDS patients and elderly persons.

Interleukin-15 enhances immune reconstitution after allogeneic bone marrow transplantation

Interleukin-15 (IL-15) is a gamma-common cytokine that plays an important role in the development, survival, and proliferation of natural killer (NK), NK T, and CD8+ T-cells. We administered IL-15 to recipients of an allogeneic bone marrow transplantation (allo BMT) to determine its effects on immune reconstitution. Posttransplantation IL-15 administration significantly increased donor-derived CD8+ T (mostly CD122(+)CD44(+)CD8+ T-cells), NK, and NK T-cells at day +28 in young and old recipients of allo BMT. This was associated with enhanced T-cell and NK-cell function. IL-15 stimulated homeostatic proliferation of donor CD8+ T-cells in recipients of carboxyfluorescein diacetate succinimidyl ester-labeled donor T-cell infusions. Posttransplantation IL-15 administration also resulted in a decrease in apoptotic CD8+ T-cells, an increase in Bcl-2-expressing CD8+ T-cells, and an increase in the fraction of Ki67+ proliferative NK and CD8+ T-cells in recipients of allo BMT. IL-15 did not exacerbate graft-versus-host disease (GVHD) in recipients of T-cell-depleted BMT but could aggravate GVHD in some cases in recipients of a T-cell-repleted BMT. Finally, we found that IL-15 administration could enhance graft-versus-leukemia activity. In conclusion, IL-15 can be administered safely to recipients of a T-cell-depleted allo BMT to enhance CD8+ T, NK, and NK T-cell reconstitution.

Passive or active immunization with myelin basic protein impairs neurological function and exacerbates neuropathology after spinal cord injury in rats

Myelin-reactive T-cells are activated by traumatic spinal cord injury (SCI) in rodents and humans. Despite the historical association of these cells with experimental and clinical neuropathology, recent data suggest a neuroprotective role for myelin-reactive T-cells. Because of the biological and therapeutic implications of these findings, we attempted to reproduce the original neuroprotective vaccine protocols in a model of rat SCI. Specifically, MBP-reactive T-cell function was enhanced in SCI rats via passive or active immunization. Locomotor function was assessed using a standardized locomotor rating scale (Basso-Beattie-Bresnahan scale) and was correlated with myelin and axon sparing. The functional and anatomical integrity of the rubrospinal pathway also was analyzed using the inclined plane test and anatomical tract tracing. MBP-immunized rats exhibited varying degrees of functional impairment, exacerbated lesion pathology, greater rubrospinal neuron loss, increased intraspinal T-cell accumulation, and enhanced macrophage activation relative to SCI control groups. These data are consistent with the conventional view of myelin-reactive T-cells as pathological effector cells.

Telomere length predicts neutrophil recovery in the absence of G-CSF after autologous peripheral blood stem cell transplantation

SUMMARY

Haemopoietic regeneration after autologous peripheral blood progenitor cell (PBPC) transplantation can be delayed in some patients despite adequate infusion of CD34(+) cells. This suggests variability in the proliferation potential of the implanted cells, a capacity that may be predicted by their telomere length. To test this theory, telomere length was measured on stored apheresis samples from 36 patients aged 46.6+/-11.1 years, who had undergone successful autologous PBPC transplantation with a median of 5.6 x 10(6)/kg (1.3 x 10(6)-36.1 x 10(6)/kg) CD34(+) cells. The mean PBPC telomere length for the cohort was 9.4+/-2.3 kbp. For patients who did not receive G-CSF post transplantation (n=7), days to absolute neutrophil recovery (ANC), >/=0.1, 0.5 and 1.0 x 10(9) cells/l, were significantly inversely correlated with telomere length of the infused PBPC (r=-0.88, -0.81, -0.77, respectively; P<0.05,). However, no correlation was found for patients who received G-CSF from day 1 post transplantation (n=20). These data suggest that for transplantation with sufficient CD34(+) cells, neutrophil recovery is less efficient in patients receiving infusions of cells with short telomeres, but this deficiency can be corrected with adequate post transplantation administration of G-CSF. Bone Marrow Transplantation (2004) 34, 439-445. doi:10.1038/sj.bmt.1704607 Published online 19 July 2004

Chimerism and clinical outcomes of 110 recipients of unrelated donor bone marrow transplants who underwent conditioning with low-dose, single-exposure total body irradiation and cyclophosphamide

We hypothesized that low-dose (550-cGy), single-exposure, high dose rate (30 cGy/min) total body irradiation (TBI) with cyclophosphamide as conditioning for HLA-compatible unrelated donor (URD) bone marrow transplantation (BMT) would result in donor chimerism (DC) with a low risk for serious organ toxicity and treatment-related mortality (TRM). Twenty-six patients with good risk diagnoses (acute leukemia in first complete remission [CR] and chronic-phase chronic myelogenous leukemia [CML]) and 84 with poor risk diagnoses underwent this regimen and URD BMT. Unsorted marrow nucleated cells were assessed for chimerism using VNTR probes. All DC occurred in 78 (86%) of 91 evaluable patients at 1 or more follow-up points. Graft failure occurred in 7 (7.7%) patients. Fatal organ toxicity occurred in only 2% of patients. TRM rates through 2 years of follow-up were 19% and 42% in those with good and poor risk diagnoses, respectively. Overall and disease-free survival rates in the good risk group were 47% and 40%, respectively, and in the poor risk group they were 25% and 21%, respectively, at a median follow-up for living patients of 850 days (range, 354-1588 days). This regimen resulted in 100% DC in most patients undergoing URD BMT with a relatively low risk for fatal organ toxicity and TRM.