A unique immune signature in blood separates therapy-refractory from therapy-responsive acute graft-versus-host disease.

Acute graft-versus-host disease (aGVHD) is an immune cell‒driven, potentially lethal complication of allogeneic hematopoietic stem cell transplantation affecting diverse organs, including the skin, liver, and gastrointestinal (GI) tract. We applied mass cytometry (CyTOF) to dissect circulating myeloid and lymphoid cells in children with severe (grade III-IV) aGVHD treated with immune suppressive drugs alone (first-line therapy) or in combination with mesenchymal stromal cells (MSCs; second-line therapy). These results were compared with CyTOF data generated in children who underwent transplantation with no aGVHD or age-matched healthy control participants. Onset of aGVHD was associated with the appearance of CD11b+CD163+ myeloid cells in the blood and accumulation in the skin and GI tract. Distinct T-cell populations, including TCRγδ+ cells, expressing activation markers and chemokine receptors guiding homing to the skin and GI tract were found in the same blood samples. CXCR3+ T cells released inflammation-promoting factors after overnight stimulation. These results indicate that lymphoid and myeloid compartments are triggered at aGVHD onset. Immunoglobulin M (IgM) presumably class switched, plasmablasts, and 2 distinct CD11b- dendritic cell subsets were other prominent immune populations found early during the course of aGVHD in patients refractory to both first- and second-line (MSC-based) therapy. In these nonresponding patients, effector and regulatory T cells with skin- or gut-homing receptors also remained proportionally high over time, whereas their frequencies declined in therapy responders. Our results underscore the additive value of high-dimensional immune cell profiling for clinical response evaluation, which may assist timely decision-making in the management of severe aGVHD.

Anti-T-lymphocyte globulin exposure is associated with acute graft-versus-host disease and relapse in pediatric acute lymphoblastic leukemia patients undergoing hematopoietic stem cell transplantation: a multinational prospective study.

Anti T-lymphocyte globulin (ATLG) is used in hematopoietic stem cell transplantation (HSCT) to prevent graft-versus-host disease (GvHD) and graft failure. To date, insight in ATLG pharmacokinetics and -dynamics (PK/PD) is limited, and population PK (POPPK) models are lacking. In this prospective study, we describe ATLG POPPK using NONMEM® and the impact of ATLG exposure on clinical outcome and immune reconstitution in a homogeneous cohort of pediatric acute lymphoblastic leukemia (ALL) patients transplanted with a matched unrelated donor and receiving uniform ATLG dosing. Based on 121 patients and 812 samples for POPPK analysis, a two-compartmental model with parallel linear and non-linear clearance and bodyweight as covariate, best described the ATLG concentrationtime data. The level of ATLG exposure (day active ATLG day 16 8.2%, p.

Development and Validation of an Efficient and Highly Sensitive Enzyme-Linked Immunosorbent Assay for Alemtuzumab Quantification in Human Serum and Plasma.

BACKGROUND: Alemtuzumab is a humanized monoclonal antibody that targets the CD52 glycoprotein expressed on most lymphocytes, subsequently inducing complement-mediated and antibody-mediated cytotoxicity. Owing to its ability to induce profound immune depletion, alemtuzumab is frequently used in patients before allogeneic hematopoietic stem cell transplantation to prevent graft rejection and acute graft-versus-host disease. In this clinical context, a stable immunoassay with high sensitivity and specificity to determine alemtuzumab levels is essential for performing pharmacokinetic and pharmacodynamic analyses; however, the available methods have several limitations. Here, we report the successful development and validation of an efficient and highly sensitive enzyme-linked immunosorbent assay technique based on commercially available reagents to quantify alemtuzumab in human serum or plasma. METHODS: This enzyme-linked immunosorbent assay technique was developed and validated in accordance with the European Medicines Agency guidelines on bioanalytical method validation. RESULTS: The assay sensitivity (lower limit of quantification) is 0.5 ng·mL -1 , and the dynamic range is 0.78-25 ng·mL -1 . To accommodate quantification of peak concentration and concentrations below the lympholytic level (<0.1 mcg·mL -1 ), patients' serum samples were prediluted 20-400 times according to the expected alemtuzumab concentration. The overall within-run accuracy was between 96% and 105%, whereas overall within-run precision (coefficient of variation) was between 3% and 9%. The between-run assessment provided an overall accuracy between 86% and 95% and an overall coefficient of variation between 5% and 14%. CONCLUSIONS: The developed assay provides accurate insight into alemtuzumab exposure and its effects on the clinical response to treatment, which is key to optimizing treatment strategies.

IL-7 and IL-15 Levels Reflect the Degree of T Cell Depletion during Lymphopenia and Are Associated with an Expansion of Effector Memory T Cells after Pediatric Hematopoietic Stem Cell Transplantation.

Differentially and functionally distinct T cell subsets are involved in the development of complications after allogeneic hematopoietic stem cell transplantation (HSCT), but little is known about factors regulating their recovery after HSCT. In this study, we investigated associations between immune-regulating cytokines, T cell differentiation, and clinical outcomes. We included 80 children undergoing allogeneic HSCT for acute leukemia using bone marrow or peripheral blood stem cells grafted from a matched sibling or unrelated donor. Cytokines (IL-7, IL-15, IL-18, SCF, IL-6, IL-2, and TNF-α) and active anti-thymocyte globulin (ATG) levels were longitudinally measured along with extended T cell phenotyping. The cytokine profiles showed a temporary rise in IL-7 and IL-15 during lymphopenia, which was strongly dependent on exposure to active ATG. High levels of IL-7 and IL-15 from graft infusion to day +30 were predictive of slower T cell recovery during the first 2 mo post-HSCT; however, because of a major expansion of memory T cell stages, only naive T cells remained decreased after 3 mo (p < 0.05). No differential effect was seen on polarization of CD4+ T cells into Th1, Th2, or Th17 cells or regulatory T cells. Low levels of IL-7 and IL-15 at day +14 were associated with acute graft-versus-host disease grades II-IV in ATG-treated patients (p = 0.0004 and p = 0.0002, respectively). Children with IL-7 levels comparable to healthy controls at day +14 post-HSCT were less likely to develop EBV reactivation posttransplant. These findings suggest that quantification of IL-7 and IL-15 may be useful as biomarkers in assessing the overall T cell depletion and suggest a potential for predicting complications after HSCT.

Mutations in DNMT3B Modify Epigenetic Repression of the D4Z4 Repeat and the Penetrance of Facioscapulohumeral Dystrophy.

Facioscapulohumeral dystrophy (FSHD) is associated with somatic chromatin relaxation of the D4Z4 repeat array and derepression of the D4Z4-encoded DUX4 retrogene coding for a germline transcription factor. Somatic DUX4 derepression is caused either by a 1-10 unit repeat-array contraction (FSHD1) or by mutations in SMCHD1, which encodes a chromatin repressor that binds to D4Z4 (FSHD2). Here, we show that heterozygous mutations in DNA methyltransferase 3B (DNMT3B) are a likely cause of D4Z4 derepression associated with low levels of DUX4 expression from the D4Z4 repeat and increased penetrance of FSHD. Recessive mutations in DNMT3B were previously shown to cause immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome. This study suggests that transcription of DUX4 in somatic cells is modified by variations in its epigenetic state and provides a basis for understanding the reduced penetrance of FSHD within families.

Risk Factors, Treatment, and Immune Dysregulation in Autoimmune Cytopenia after Allogeneic Hematopoietic Stem Cell Transplantation in Pediatric Patients.

Autoimmune or alloimmune cytopenia (AIC) is a known rare complication of hematopoietic stem cell transplantation (SCT). AIC after SCT is considered difficult to treat and is associated with high morbidity and mortality. In this retrospective study in pediatric patients we evaluated incidence, outcome, potential risk factors, and current treatment strategies. A nested matched case-control study was performed to search for biomarkers associated with AIC. Of 531 consecutive SCTs at our center between 2000 and 2016, 26 were complicated by the development of AIC (cumulative incidence, 5.0%) after a median of 5 months post-SCT. Autoimmune hemolytic anemia was the most common AIC with 12 patients (46%). We identified nonmalignant disease, alemtuzumab serotherapy pre-SCT, and cytomegalovirus (CMV) reactivation as independently associated risk factors. The cytokine profile of patients at the time of AIC diagnosis appeared to skew toward a more pronounced Th 2 response compared with control subjects at the corresponding time point post-SCT. Corticosteroids and intravenous immunoglobulin as first-line treatment or a wait-and-see approach led to resolution of AIC in 35% of cases. Addition of step-up therapies rituximab (n = 15), bortezomib (n = 7), or sirolimus (n = 3) was associated with AIC resolution in 40%, 57%, and 100% of cases, respectively. In summary, we identified CMV reactivation post-SCT as a new clinical risk factor for the development of AIC in children. The cytokine profile during AIC appears to favor a Th 2 response. Rituximab, bortezomib, and sirolimus are promising step-up treatment modalities.

Human Lymphoid Tissues Harbor a Distinct CD69+CXCR6+ NK Cell Population.

Knowledge of human NK cells is based primarily on conventional CD56(bright) and CD56(dim) NK cells from blood. However, most cellular immune interactions occur in lymphoid organs. Based on the coexpression of CD69 and CXCR6, we identified a third major NK cell subset in lymphoid tissues. This population represents 30-60% of NK cells in marrow, spleen, and lymph node but is absent from blood. CD69(+)CXCR6(+) lymphoid tissue NK cells have an intermediate expression of CD56 and high expression of NKp46 and ICAM-1. In contrast to circulating NK cells, they have a bimodal expression of the activating receptor DNAX accessory molecule 1. CD69(+)CXCR6(+) NK cells do not express the early markers c-kit and IL-7Rα, nor killer cell Ig-like receptors or other late-differentiation markers. After cytokine stimulation, CD69(+)CXCR6(+) NK cells produce IFN-γ at levels comparable to CD56(dim) NK cells. They constitutively express perforin but require preactivation to express granzyme B and exert cytotoxicity. After hematopoietic stem cell transplantation, CD69(+)CXCR6(+) lymphoid tissue NK cells do not exhibit the hyperexpansion observed for both conventional NK cell populations. CD69(+)CXCR6(+) NK cells constitute a separate NK cell population with a distinct phenotype and function. The identification of this NK cell population in lymphoid tissues provides tools to further evaluate the cellular interactions and role of NK cells in human immunity.

Deletion of the entire interferon-γ receptor 1 gene causing complete deficiency in three related patients.

PURPOSE: Complete interferon-γ receptor 1 (IFN-γR1) deficiency is a primary immunodeficiency causing predisposition to severe infection due to intracellular pathogens. Only 36 cases have been reported worldwide. The purpose of this article is to describe a large novel deletion found in 3 related cases, which resulted in the complete removal of the IFNGR1 gene. METHODS: Whole blood from three patients was stimulated with lipopolysaccharide (LPS) and IFN-γ to determine production of tumor necrosis factor (TNF), interleukin-12 p40 (IL-12p40) and IL-10. Expression of IFN-γR1 on the cell membrane of patients' monocytes was assessed using flow cytometry. IFNGR1 transcript was analyzed in RNA and the gene and adjacent regions were analyzed in DNA. Finally, IL22RA2 transcript levels were analyzed in whole blood cells and dendritic cells. RESULTS: There was no expression of the IFN-γR1 on the monocytes. Consistent with this finding, there was no IFN-γ response in the whole blood assay as measured by effect on LPS-induced IL-12p40, TNF and IL-10 production. A 119.227 nt homozygous deletion on chromosome 6q23.3 was identified, removing the IFNGR1 gene completely and ending 117 nt upstream of the transcription start of the IL22RA2 gene. Transcript levels of IL22RA2 were similar in patient and control. CONCLUSIONS: We identified the first large genomic deletion of IFNGR1 causing complete IFN-γR1 deficiency. Despite the deletion ending very close to the IL22RA2 gene, it does not appear to affect IL22RA2 transcription and, therefore, may not have any additional clinical consequence.

Neuronal antibodies in pediatric epilepsy: Clinical features and long-term outcomes of a historical cohort not treated with immunotherapy.

OBJECTIVE: In autoimmune encephalitis the etiologic role of neuronal cell-surface antibodies is clear; patients diagnosed and treated early have better outcomes. Neuronal antibodies have also been described in patients with pediatric epilepsy without encephalitis. The aim was to assess whether antibody presence had any effect on long-term outcomes in these patients. METHODS: Patients (n = 178) were recruited between 1988 and 1992 as part of the prospective Dutch Study of Epilepsy in Childhood; none received immunotherapy. Healthy age-matched bone-marrow donors served as controls (n = 112). All sera were tested for serum N-methyl-d-aspartate receptor (NMDAR), alpha amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, leucine rich glioma inactivated 1, contactin associated protein like 2 (CASPR2), contactin-2, glutamic acid decarboxylase, and voltage gated potassium channel (VGKC)-complex antibodies by standard techniques. No cerebrospinal fluid (CSF) samples were available. Results were correlated with clinical data collected over 15 years. RESULTS: Seventeen patients (9.5%) were positive for VGKC complex (n = 3), NMDAR (n = 7), CASPR2 (n = 4), and contactin-2 (n = 3), compared to three (3/112; 2.6%) healthy controls (VGKC complex [n = 1], NMDAR [n = 2]; p = 0.03; Fisher's exact test). Titers were relatively low (≤1:100 for cell-surface antibodies), but 8 (47%) of the 17 positive samples bound to the surface of live hippocampal neurons consistent with a potential pathogenic antibody. Preexisting cognitive impairment was more frequent in antibody-positive patients (9/17 vs. 33/161; p = 0.01). Fourteen antibody-positive patients were treated with standard antiepileptic drugs (AEDs); three (17%) became intractable but this was not different from the 16 (10%) of 161 antibody-negative patients. In 96 patients with available follow-up samples at 6 and/or 12 months, 6 of 7 positive antibodies had disappeared and, conversely, antibodies had appeared for the first time in a further 7 patients. SIGNIFICANCE: Neuronal antibodies were found at low levels in 9.5% of patients with new-onset pediatric epilepsy but did not necessarily persist over time, and the development of antibodies de novo in later samples suggests they could be due to a secondary response to neuronal damage or inflammation. Moreover, as the response to standard AEDs and the long-term outcome did not differ from those of antibody-negative pediatric patients, these findings suggest that routine neuronal antibody testing is unlikely to be helpful in pediatric epilepsy. However, the higher incidence of preexisting cognitive problems in the antibody-positive group, the CASPR2 and contactin-2 antibodies in 7 of 17 patients, and the binding of 8 of 17 of serum samples to live hippocampal neurons suggest that neuronal antibodies, even if secondary, could contribute to the comorbidities of pediatric epilepsy.

The effect of cidofovir on adenovirus plasma DNA levels in stem cell transplantation recipients without T cell reconstitution.

Cidofovir is frequently used to treat life-threatening human adenovirus (HAdV) infections in immunocompromised children after hematopoietic stem cell transplantation (HSCT). However, the antiviral effect irrespective of T cell reconstitution remains unresolved. Plasma HAdV DNA levels were monitored by real-time quantitative PCR during 42 cidofovir treatment episodes for HAdV viremia in 36 pediatric allogeneic HSCT recipients. HAdV load dynamics were related to T and natural killer (NK) cell reconstitution measured by flow cytometry. To evaluate the in vivo antiadenoviral effect of cidofovir, we focused on 20 cidofovir treatment episodes lacking concurrent T cell reconstitution. During 2 to 10 weeks of follow-up in the absence of T cells, HAdV load reduction (n = 7) or stabilization (n = 8) was observed in 15 of 20 treatments. Although HAdV load reduction was always accompanied by NK cell expansion, HAdV load stabilization was measured in 2 children lacking both T and NK cell reconstitution. In cases with T cell reconstitution, rapid HAdV load reduction (n = 14) or stabilization (n = 6) was observed in 20 of 22 treatments. In the absence of T cells, cidofovir treatment was associated with HAdV viremia control in the majority of cases. Although the contribution of NK cells cannot be excluded, cidofovir has the potential to mediate HAdV load stabilization in the time pending T cell reconstitution.

Impact of serotherapy on immune reconstitution and survival outcomes after stem cell transplantations in children: thymoglobulin versus alemtuzumab.

The outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is strongly affected by the kinetics of reconstitution of the immune system. This study compared the effects of antithymocyte globulin (ATG) and alemtuzumab on various outcome parameters after HSCT. The study cohort consisted of 148 children, with a median age of 9.6 years (range, .4 to 19.0), who underwent HSCT for malignant and benign hematological disorders in a single HSCT unit. Conditioning included ATG (n = 110) or alemtuzumab (n = 38). Cox proportional hazard regression analysis showed that alemtuzumab significantly delayed the recovery of CD3(+) T cells and CD4(+)as well as CD8(+) T cell subsets (P ≤ .001) and natural killer (NK) cells (P = .008) compared with ATG. In both ATG- and alemtuzumab-treated patients, shorter drug exposure lead to significantly faster recovery of T cells. Alemtuzumab was associated with lower donor chimerism 3 and 6 months after transplantation and a higher risk of disease relapse (P = .001). The overall survival and event-free survival risks were significantly lower for alemtuzumab-treated patients (P = .020 and P < .001, respectively). Patients who received alemtuzumab showed a trend to lower risk of acute graft-versus-host disease, more human adenovirus, and less Epstein-Barr virus reactivations compared with patients who received ATG. These data indicate that children treated with alemtuzumab as part of the conditioning regimen have a slower T cell and NK cell reconstitution compared with those treated with ATG, which compromises the overall and event-free survival. Prolonged length of lympholytic drug exposure delayed the T cell recovery in both ATG- and alemtuzumab-treated patients. Therefore, we recommend detailed pharmacokinetic/pharmacodynamic (PK/PD) analyses in a larger cohort of patients to develop an algorithm aiming at optimization of the serotherapy containing conditioning regimen.

Role of NKG2D, DNAM-1 and natural cytotoxicity receptors in cytotoxicity toward rhabdomyosarcoma cell lines mediated by resting and IL-15-activated human natural killer cells.

Children with advanced stages (relapsed/refractory and stage IV) of rhabdomyosarcoma (RMS) have a poor prognosis despite intensive chemotherapy and autologous stem cell rescue, with 5-year survival rates ranging from 5 to 35 %. Development of new, additional treatment modalities is necessary to improve the survival rate. In this preclinical study, we investigated the potential of resting and cytokine-activated natural killer (NK) cells to lyse RMS cell lines, as well as the pathways involved, to explore the eventual clinical application of (activated) NK cell immunotherapy. RMS cell lines (n = 3 derived from embryonal RMS and n = 2 derived from alveolar RMS) were susceptible to cytolysis mediated by resting NK cells, and this susceptibility was significantly increased using IL-15-activated NK cells. Flow cytometry and cytolytic assays were used to define the activating and inhibitory pathways of NK cells involved in recognizing and lysing RMS cells. NKG2D and DNAM-1 receptor-ligand interactions were essential in cytolysis by resting NK cells, as simultaneous blocking of both pathways resulted in almost complete abrogation of the cytotoxicity. In contrast, combined blocking of DNAM-1 and NKG2D only led to partial reduction of the lytic activity of IL-15-activated NK cells. In this respect, residual lysis was, at least partly, mediated by pathways involving the natural cytotoxicity receptors NKp30 and NKp46. These findings support further exploration of NK cell-based immunotherapy as adjuvant modality in current treatment strategies of RMS.

Gene-expression and in vitro function of mesenchymal stromal cells are affected in juvenile myelomonocytic leukemia.

An aberrant interaction between hematopoietic stem cells and mesenchymal stromal cells has been linked to disease and shown to contribute to the pathophysiology of hematologic malignancies in murine models. Juvenile myelomonocytic leukemia is an aggressive malignant disease affecting young infants. Here we investigated the impact of juvenile myelomonocytic leukemia on mesenchymal stromal cells. Mesenchymal stromal cells were expanded from bone marrow samples of patients at diagnosis (n=9) and after hematopoietic stem cell transplantation (n=7; from 5 patients) and from healthy children (n=10). Cells were characterized by phenotyping, differentiation, gene expression analysis (of controls and samples obtained at diagnosis) and in vitro functional studies assessing immunomodulation and hematopoietic support. Mesenchymal stromal cells from patients did not differ from controls in differentiation capacity nor did they differ in their capacity to support in vitro hematopoiesis. Deep-SAGE sequencing revealed differential mRNA expression in patient-derived samples, including genes encoding proteins involved in immunomodulation and cell-cell interaction. Selected gene expression normalized during remission after successful hematopoietic stem cell transplantation. Whereas natural killer cell activation and peripheral blood mononuclear cell proliferation were not differentially affected, the suppressive effect on monocyte to dendritic cell differentiation was increased by mesenchymal stromal cells obtained at diagnosis, but not at time of remission. This study shows that active juvenile myelomonocytic leukemia affects the immune response-related gene expression and function of mesenchymal stromal cells. In contrast, the differential gene expression of hematopoiesis-related genes could not be supported by functional data. Decreased immune surveillance might contribute to the therapy resistance and progression in juvenile myelomonocytic leukemia.

Early cytomegalovirus reactivation leaves a specific and dynamic imprint on the reconstituting T cell compartment long-term after hematopoietic stem cell transplantation.

Human cytomegalovirus (CMV) reactivation frequently occurs during the early phase of immune recovery after allogeneic hematopoietic stem cell transplantation (HSCT). Whereas the recovery of virus-specific immunity in the early phase after HSCT is extensively studied, the impact of CMV on the reconstitution and composition of the T cell compartment long-term after HSCT is unknown. We analyzed T cell reconstitution 1 to 2 years after HSCT in 131 pediatric patients. One year after HSCT, patients with early CMV reactivation (n = 46) had 3-fold higher CD8(+) T cell numbers (median, 1323 versus 424 cells/µL; P < .0001) compared with patients without CMV reactivation (n = 85). This effect, caused by a major expansion of CD8(+) effector memory (EM) and end-stage effector (EMRA) T cells, was independent of pretransplantation donor and recipient CMV serostatus and not seen after Epstein-Barr virus or adenovirus reactivations. At 1 and 2 years after HSCT, the absolute numbers of CD8(+) naive and central memory T cells, as well as CD4(+) naive, CM, EM, and EMRA T cells, did not differ between patients with or without CMV reactivation. In the second year after HSCT, a significant contraction of the initially expanded CD8(+) EM and EMRA T cell compartments was observed in patients with early CMV reactivation. In conclusion, CMV reactivation early after pediatric HSCT leaves a specific and dynamic imprint on the size and composition of the CD8(+) T cell compartment without compromising the reconstitution of CD8(+) and CD4(+) naive and central memory T cells pivotal in the response to neo and recall antigens.

Mutations in ZBTB24 are associated with immunodeficiency, centromeric instability, and facial anomalies syndrome type 2.

Autosomal-recessive immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is mainly characterized by recurrent, often fatal, respiratory and gastrointestinal infections. About 50% of patients carry mutations in the DNA methyltransferase 3B gene (DNMT3B) (ICF1). The remaining patients carry unknown genetic defects (ICF2) but share with ICF1 patients the same immunological and epigenetic features, including hypomethylation of juxtacentromeric repeat sequences. We performed homozygosity mapping in five unrelated ICF2 patients with consanguineous parents and then performed whole-exome sequencing in one of these patients and Sanger sequencing in all to identify mutations in the zinc-finger- and BTB (bric-a-bric, tramtrack, broad complex)-domain-containing 24 (ZBTB24) gene in four consanguineously descended ICF2 patients. Additionally, we found ZBTB24 mutations in an affected sibling pair and in one patient for whom it was not known whether his parents were consanguineous. ZBTB24 belongs to a large family of transcriptional repressors that include members, such as BCL6 and PATZ1, with prominent regulatory roles in hematopoietic development and malignancy. These data thus indicate that ZBTB24 is involved in DNA methylation of juxtacentromeric DNA and in B cell development and/or B and T cell interactions. Because ZBTB24 is a putative DNA-binding protein highly expressed in the lymphoid lineage, we predict that by studying the molecular function of ZBTB24, we will improve our understanding of the molecular pathophysiology of ICF syndrome and of lymphocyte biology in general.

Gastrointestinal acute graft-versus-host disease in children: histology for diagnosis, mesenchymal stromal cells for treatment, and biomarkers for prediction of response.

Steroid-nonresponsive acute graft-versus-host disease (aGVHD) after hematopoietic stem cell transplantation carries a poor prognosis. Various groups have reported beneficial effects of mesenchymal stromal cell (MSC) infusion as salvage treatment. Response to treatment is typically evaluated using the diagnostic clinical criteria for aGVHD. In this study, we evaluated the usefulness of additional gastrointestinal biopsy specimens paired with serum biomarkers. In a cohort of 22 pediatric patients, persistent or recurrent diarrhea was seen in 18 children treated with MSC infusion for steroid-refractory aGVHD. To exclude other causes of gastrointestinal pathology, patients were biopsied for histological analysis. Eight of 12 patients exhibited residual tissue damage and villous atrophy, but no active aGVHD. Serum biomarkers have been identified as an alternative tool for monitoring the response to aGVHD treatment. The value of biomarkers for inflammation, tissue, and endothelial cell damage was evaluated in our cohort. Although predictive of response to treatment and survival, these markers lack the necessary specificity and sensitivity to predict response to MSC therapy. Objective endpoints for clinical trials on the treatment of steroid-refractory aGVHD remain to be defined. Thus, we recommend including biopsies and biomarkers to discriminate between ongoing aGVHD and postinflammatory malabsorption.

Multiple infusions of mesenchymal stromal cells induce sustained remission in children with steroid-refractory, grade III-IV acute graft-versus-host disease.

Mesenchymal stromal cell (MSC) infusions have been reported to be effective in patients with steroid-refractory, acute graft-versus-host disease (aGvHD) but comprehensive data on paediatric patients are limited. We retrospectively analysed a cohort of 37 children (aged 3 months-17 years) treated with MSCs for steroid-refractory grade III-IV aGvHD. All patients but three received multiple MSC infusions. Complete response (CR) was observed in 24 children (65%), while 13 children had either partial (n = 8) or no response (n = 5). Cumulative incidence of transplantation-related mortality (TRM) in patients who did or did not achieve CR was 17% and 69%, respectively (P = 0.001). After a median follow-up of 2.9 years, overall survival (OS) was 37%; it was 65% vs. 0% in patients who did or did not achieve CR, respectively (P = 0.001). The median time from starting steroids for GvHD treatment to first MSC infusion was 13 d (range 5-85). Children treated between 5 and 12 d after steroid initiation showed a trend for better OS (56%) and lower TRM (17%) as compared with patients receiving MSCs 13-85 d after steroids (25% and 53%, respectively; P = 0.22 and 0.06, respectively). Multiple MSC infusions are safe and effective for children with steroid-refractory aGvHD, especially when employed early in the disease course.

Antibody-dependent cell lysis by NK cells is preserved after sarcoma-induced inhibition of NK cell cytotoxicity.

Osteosarcoma and Ewing's sarcoma tumor cells are susceptible to IL15-induced or antibody-mediated cytolytic activity of NK cells in short-term cytotoxicity assays. When encountering the tumor environment in vivo, NK cells may be in contact with tumor cells for a prolonged time period. We explored whether a prolonged interaction with sarcoma cells can modulate the activation and cytotoxic activity of NK cells. The 40 h coculture of NK cells with sarcoma cells reversibly interfered with the IL15-induced expression of NKG2D, DNAM-1 and NKp30 and inhibited the cytolytic activity of NK cells. The inhibitory effects on receptor expression required physical contact between NK cells and sarcoma cells and were independent of TGF-ß. Five days pre-incubation of NK cells with IL15 prevented the down-regulation of NKG2D and cytolytic activity in subsequent cocultures with sarcoma cells. NK cell FcγRIIIa/CD16 receptor expression and antibody-mediated cytotoxicity were not affected after the coculture. Inhibition of NK cell cytotoxicity was directly linked to the down-regulation of the respective NK cell-activating receptors. Our data demonstrate that the inhibitory effects of sarcoma cells on the cytolytic activity of NK cells do not affect the antibody-dependent cytotoxicity and can be prevented by pre-activation of NK cells with IL15. Thus, the combination of cytokine-activated NK cells and monoclonal antibody therapy may be required to improve tumor targeting and NK cell functionality in the tumor environment.

Mesenchymal stromal cells isolated from children with systemic juvenile idiopathic arthritis suppress innate and adaptive immune responses.

BACKGROUND AIMS: Infusion of mesenchymal stromal cells (MSCs) has been reported to be an effective treatment modality for acute graft-versus-host disease, and MSCs have been considered for use in the treatment of patients with autoimmune diseases. Before contemplating clinical studies with MSCs in patients with systemic juvenile idiopathic arthritis (sJIA), the immunomodulatory capacity of MSCs in this setting needs to be explored. A comparative analysis of bone marrow-derived MSCs from children with sJIA and healthy pediatric controls was performed. METHODS: MSCs were successfully expanded from 11 patients with sJIA and 10 controls. The phenotype, differentiation and immunomodulatory capacity of these MSCs were compared. The effect of immunosuppressive drugs on MSC function was also investigated. RESULTS: MSCs from patients with sJIA and controls showed no differences in their suppressive effect using control peripheral blood mononuclear cells. Furthermore, the suppression of the response of peripheral blood mononuclear cells from patients with sJIA by autologous sJIA MSCs and allogeneic control MSCs was comparable. The immunosuppressive effect of both groups of MSCs was diminished in the presence of indomethacin (P < 0.05). MSCs from patients with sJIA and controls suppressed interleukin-2-induced natural killer cell activation to a similar extent. In addition, MSCs of patients with sJIA and controls inhibited the differentiation of monocytes to dendritic cells. CONCLUSIONS: This is the first explorative study in a significant cohort of patients with sJIA to evaluate the effect of MSCs on adaptive and innate immune responses. The comparable immunosuppressive characteristics of MSCs derived from patients with sJIA to age-matched controls support the potential use of patient-derived MSCs in the treatment of sJIA.