Pretransplantation predictors of survival in nonremission acute myeloid leukemia treated with haploidentical transplantation using steroid-based GVHD prophylaxis.

Haploidentical hematopoietic cell transplantation (HCT) using glucocorticoids for acute graft-versus-host disease prophylaxis (GC-haplo) may become a curative treatment option for nonremission acute myeloid leukemia (AML). This retrospective study aimed to identify pre-HCT predictors of survival in a cohort of 97 nonremission AML treated with GC-haplo in Hyogo Medical University Hospital between 2010 and 2020. Relapse and primary induction failure included in 70 (72%) and 27 (28%) patients, respectively. Sixty-one patients (63%) had undergone previous HCT. Multivariate analysis revealed that ≤ 6 months' duration between first complete remission (CR1) and first relapse (Rel1) (CR1-Rel1 interval) (hazard ratio 2.11, 95% confidence interval [CI] 1.15-3.89, P = 0.016) and serum albumin before starting the conditioning treatment of ≤ 3.5 g/dL (hazard ratio 1.80, 95%CI 1.09-2.96, P = 0.022) as risk factors for overall survival. Among three groups categorized according to serum albumin and CR1-Rel1 interval, the best 3-year overall survival was observed in patients with albumin > 3.5 g/dL and CR1-Rel1 interval > 6 months or primary induction failure (50.2%, 95%CI 28.9%-68.3%, P < 0.001), revealing that survival could be predicted using albumin and past CR duration in patients with very high-risk AML not in remission before GC-haplo.

Individualized rabbit anti-thymocyte globulin dosing in adult haploidentical hematopoietic cell transplantation with high-risk hematologic malignancy: Exposure-response analysis and population pharmacokinetics simulations.

Hematopoietic cell transplantation (HCT) for hematologic malignancies with non-remission disease and/or prior post-transplant relapse have poor relapse-free survival. We previously demonstrated the efficacy of haploidentical reduced-intensity HCT regimen with glucocorticoid-based graft-versus-host disease (GVHD) prophylaxis. We recently showed a possible association between rabbit antithymocyte globulin (rATG) exposure and acute GVHD (aGVHD) risk, leading to hypothesize that optimization of rATG exposure may further improve this regimen. We retrospectively examined the exposure-response association of rATG and key clinical outcomes post haploidentical HCT. We subsequently developed an individualized rATG dosing that optimizes rATG exposure using a previously developed population pharmacokinetic model. Of the 103 patients analyzed, the median age was 47 years (range: 17-70) and majority had a non-remission disease prior to HCT (88%). rATG concentration on day 0 of HCT (Cday_0 ) was the strongest predictor of Grade 2-4 aGVHD through day +100. Patients with Cday_0 ≥ 20 µg/mL had an approximately 3-fold lower risk of Grade 2-4 aGVHD (hazard ratio [HR]: 0.32, 95% confidence interval [CI]: 0.16, 0.62) and Grade 3-4 aGVHD (HR: 0.33, 95% CI: 0.16, 0.68) as well as an approximately 2-fold lower risk of overall mortality (HR: 0.47, 95% CI: 0.28, 0.77) and relapse (HR: 0.50, 95% CI: 0.26, 0.94). In conclusion, this reduced-intensity haploidentical HCT regimen with exposure-optimized rATG may provide a promising option to patients undergoing high-risk HCT for hematologic malignancy. The developed rATG dosing warrant prospective validation.

Population Pharmacokinetics of Total Rabbit Anti-thymocyte Globulin in Non-obese Adult Patients Undergoing Hematopoietic Cell Transplantation for Hematologic Malignancy.

BACKGROUND AND OBJECTIVES: Rabbit anti-thymocyte globulin (rATG), a therapeutic polyclonal antibody against human T cells, is commonly used in conditioning therapy prior to allogeneic hematopoietic cell transplantation (HCT). Previous studies successfully developed an individualized rATG dosing regimen based on "active" rATG population PK (popPK) analysis, while "total" rATG can be a more logistically favorable alternative for early HCT outcomes. We conducted a novel popPK analysis of total rATG. METHODS: Total rATG concentration was measured in adult human-leukocyte antigen (HLA) mismatched HCT patients who received a low-dose rATG regimen (total 2.5-3 mg/kg) within 3 days prior to HCT. PopPK modeling and simulation was performed using nonlinear mixed effect modeling approach. RESULTS: A total of 504 rATG concentrations were available from 105 non-obese patients with hematologic malignancy (median age 47 years) treated in Japan. The majority had acute leukemia or malignant lymphoma (94%). Total rATG PK was described by a two-compartment linear model. Influential covariate relations include ideal body weight [positively on both clearance (CL) and central volume of distribution], baseline serum albumin (negatively on CL), CD4+ T cell dose (positively on CL), and baseline serum IgG (positively on CL). Simulated covariate effects predicted that early total rATG exposures were affected by ideal body weight. CONCLUSIONS: This novel popPK model described the PK of total rATG in the adult HCT patients who received a low-dose rATG conditioning regimen. This model can be used for model-informed precision dosing in the settings with minimal baseline rATG targets (T cells), and early clinical outcomes are of interest.

Severe acute heart failure during or following cytokine release syndrome after CAR T-cell therapy.

Although cardiac dysfunction after chimeric antigen receptor (CAR) T-cell therapy has been increasingly reported, the underlying dynamics and pathogenesis are not well documented. Herein, we describe the clinical presentation and treatment for two patients who developed severe acute heart failure after CAR T-cell therapy. Both cases shared several common characteristics, including the bone marrow involvement at the time of CAR T-cell therapy and early onset of cytokine release syndrome (CRS) with fever developing on the day of CAR T-cell infusion. Patients with early onset and/or severe CRS should be carefully monitored for the possibility of heart failure.

Association between the pharmacokinetics of rabbit anti-thymocyte globulin and acute graft-versus-host disease in patients who received haploidentical hematopoietic stem cell transplantation.

Anti-thymocyte globulin (ATG) is an important prophylactic drug against acute graft-versus-host disease (aGVHD) after haploidentical hematopoietic stem cell transplantation (haplo-HSCT). This study analyzed the pharmacokinetics of rabbit ATG 2.5 mg/kg and its effect against aGVHD in 24 patients undergoing unmanipulated haplo-HSCT. All patients had hematological malignancies not in remission. The median absolute lymphocyte count (ALC) before rabbit ATG administration was 9.5/µL (range 0-41/µL). The grade ≥ II aGVHD group had a significantly lower median rabbit ATG concentration on days 0 (C0) and 7 (C7) and areas under the curve on days 0-7 (AUC0-7) and 0-32 (AUC0-32) than the grade 0-I aGVHD group. Among the four parameters, C0 was the most optimal for predicting aGVHD according to the receiver-operating characteristic (ROC) analysis (area under the ROC curve 0.893; 95% confidence interval 0.738-1.000). The high C0 (≥ 27.8 µg/mL) group had significantly lower cumulative incidence of grade ≥ II aGVHD on day 100 than the low C0 (< 27.8 µg/mL) group (13.8% vs. 88.9%, p < 0.001). In haplo-HSCT, the C0 of rabbit ATG is a good predictor of grade ≥ II aGVHD, even though ALC before rabbit ATG administration is not a predictor of aGVHD.

Difference in outcomes following allogeneic hematopoietic cell transplantation for patients with acute myeloid leukemia and myelodysplastic syndromes.

To evaluate whether outcomes following allogeneic hematopoietic cell transplantation differ according to disease type, a three-way comparison for patients with de novo acute myeloid leukemia (AML) (n = 3318), AML evolving from myelodysplastic syndromes (MDS) (n = 208), and MDS with excess blasts (MDS-EB) (n = 994) was performed. The 5-year probabilities of overall survival (OS) for de novo AML, AML evolving from MDS, and MDS-EB were 60%, 42%, and 41% (p < 0.001), respectively. Multivariate analysis revealed that, compared to de novo AML, AML evolving from MDS was associated with a higher risk of NRM (p = 0.030) and MDS-EB with a higher risk of relapse (p < 0.001), both leading to lower OS (p = 0.010 and p < 0.001, respectively). These findings demonstrate inter-disease differences in post-transplant outcomes and highlight the needs to reduce NRM for AML evolving from MDS and to reduce relapse for MDS-EB.

Impact of the use of hydroxyethyl starch in granulocyte apheresis using Spectra Optia.

OBJECTIVES: To determine the impact of the use of hydroxyethyl starch (HES) in granulocyte apheresis using Spectra Optia. BACKGROUND: Granulocyte transfusion (GT) is a therapeutic option for neutropenic patients with severe bacterial or fungal infections. Recent studies in emergency medicine have shown the potential risk of using HES, which is routinely used in granulocyte apheresis to increase yield by sedimenting red blood cells. We hypothesized that the use of a newer device (Spectra Optia) would spare the need for HES. METHODS: We retrospectively compared granulocyte apheresis with HES (HES group, n = 89) and without HES (non-HES group, n = 36) using Spectra Optia. RESULTS: The granulocyte yield was significantly higher in the HES group (7.3 × 1010 vs. 2.0 × 10, p < 0.01) and was attributed to the difference in collection efficiency (36% vs. 7.7%, p < 0.01). The absolute neutrophil count on the following morning of GT was significantly higher in the HES group than in the non-HES group (2460/µl vs. 505/µl, p < 0.01). There were no significant differences in the occurrence of adverse events between the HES and non-HES groups. The renal function was unchanged in both groups after apheresis. CONCLUSIONS: We demonstrated that the advantage of using HES remained unchanged in granulocyte apheresis using Spectra Optia.

Allogeneic hematopoietic stem cell transplantation from a 2-HLA-haplotype-mismatched family donor for posttransplant relapse: a prospective phase I/II study.

HLA haploidentical hematopoietic stem cell transplantation (HSCT), i.e., HSCT from a 1-HLA-haplotype-mismatched family donor, has been successfully performed even as a second transplantation for posttransplant relapse. Is the haploidentical the limit of HLA mismatches in HSCT? In order to explore the possibility of HLA-mismatched HSCT from family donors beyond haploidentical relatives, we conducted a prospective phase I/II study of 2-HLA-haplotype-mismatched HSCT (2-haplo-mismatch HSCT). We enrolled 30 patients with posttransplant relapse (acute myeloid leukemia: 18, acute lymphoblastic leukemia: 11, non-Hodgkin lymphoma: 1). 2-haplo-mismatch HSCT was performed as the second to sixth transplantations. The donors were siblings (n = 12), cousins (n = 16), and second cousins (n = 2). The conditioning regimen consisted of fludarabine, cytarabine, melphalan, low-dose anti-thymocyte globulin, and 3 Gy of total body irradiation. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus, methylprednisolone, and mycophenolate mofetil. All patients achieved neutrophil engraftment, except for a case of early death. The cumulative incidences of grades II-IV and III-IV acute GVHD were 36.7% and 16.7%, respectively. The overall survival at 1 year, relapse, and non-relapse mortality rates was 30.1%, 38.9%, and 44.3%, respectively. Considering the poor prognosis of posttransplant relapse, 2-haplo-mismatch HSCT can be an alternative option in a second or third transplantation.

Predictive value of interim FDG-PET/CT findings in patients with diffuse large B-cell lymphoma treated with R-CHOP.

Objectives: To examine the prognostic value of interim 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) findings after 2-4 cycles of rituximab, plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) in patients with diffuse large B-cell lymphoma (DLBCL) receiving standardized treatment. Results: After a median 3.36 years (range 0.33 to 9.14 years), 24 of the 80 patients had documented relapse. In Interim-PET findings, 2-year PFS was significantly shorter for PET-positive as compared with PET-negative patients (50.0% vs. 86.4%; p = 0.0012). In End-PET findings, 2-year PFS was significantly shorter for PET-positive as compared with PET-negative patients (25.0% vs. 84.7%; p < 0.0001). The positive predictive value (PPV) and negative predictive value (NPV) of Interim-PET for predicting relapse or disease progression were 57.1% and 75.8%, respectively, while those for End-PET were 75.0% and 75.0%, respectively. Methods: Eighty DLBCL patients treated with first-line 6-8 R-CHOP courses regardless of interim imaging findings were enrolled. Each underwent FDG-PET/CT scanning at staging, and again during (Interim-PET) and at the end of (End-PET) therapy. PET positivity or negativity at Interim-PET and End-PET as related to progression-free survival (PFS) was examined using Kaplan-Meier analysis. Conclusion: Mid-treatment FDG-PET/CT findings may be useful for determining disease status in patients with DLBCL undergoing induction R-CHOP chemotherapy, though are not recommended for treatment decisions as part of routine clinical practice.

Safety and efficacy of amnion-derived mesenchymal stem cells (AM01) in patients with steroid-refractory acute graft-versus-host disease after allogeneic haematopoietic stem cell transplantation: a study protocol for a phase I/II Japanese trial.

INTRODUCTION: Regenerative medicine and cell therapies have been gaining much attention among clinicians. Therapeutic infusion of mesenchymal stromal cells (MSCs) is now a leading investigational strategy for the treatment of acute graft-versus-host disease (aGVHD). Bone marrow MSCs are approved for manufacture and marketing as a cell therapy for aGVHD. Our non-clinical studies confirmed that human amnion-derived MSCs had immunomodulatory activity equal to or higher than that of human bone marrow MSCs. This study will aim to evaluate the safety and efficacy of amnion-derived MSCs (AM01) in patients with steroid-refractory aGVHD. METHODS AND ANALYSIS: This study will be a multicentre, single-arm, open-label trial (an interventional study). This clinical trial will begin with a low-dose group, and when safety has been confirmed in at least three cases in the low-dose group, treatment will begin for the high-dose group, for which the safety will also be verified. The primary endpoint is to assess the safety of intravenous infusion therapy of AM01 within 24 hours after intravenous infusion of AM01. The secondary endpoint is to explore the efficacy of intravenous infusion therapy with AM01. ETHICS AND DISSEMINATION: The institutional review boards of all participating hospitals approved this study protocol (latest V3.3.0, 3 August 2018). Final data will be publicly announced. A report releasing the study results will be submitted for publication to an appropriate peer-reviewed journal. TRIAL REGISTRATION NUMBER: UMIN000029945.

Host NLRP6 exacerbates graft-versus-host disease independent of gut microbial composition.

Host NOD-like receptor family pyrin domain-containing 6 (NLRP6) regulates innate immune responses and gastrointestinal homeostasis. Its protective role in intestinal colitis and tumorigenesis is dependent on the host microbiome. Host innate immunity and microbial diversity also play a role in the severity of allogeneic immune-mediated gastrointestinal graft-versus-host disease (GVHD), the principal toxicity after allogeneic haematopoietic cell transplantation. Here, we examined the role of host NLRP6 in multiple murine models of allogeneic bone marrow transplantation. In contrast to its role in intestinal colitis, host NLRP6 aggravated gastrointestinal GVHD. The impact of host NLRP6 deficiency in mitigating GVHD was observed regardless of co-housing, antibiotic treatment or colonizing littermate germ-free wild-type and NLRP6-deficient hosts with faecal microbial transplantation from specific pathogen-free wild-type and Nlrp6-/- animals. Chimaera studies were performed to assess the role of NLRP6 expression on host haematopoietic and non-haematopoietic cells. The allogeneic [B6Ly5.2 → Nlrp6-/-] animals demonstrated significantly improved survival compared to the allogeneic [B6Ly5.2 → B6] animals, but did not alter the therapeutic graft-versus-tumour effects after haematopoietic cell transplantation. Our results unveil an unexpected, pathogenic role for host NLRP6 in gastrointestinal GVHD that is independent of variations in the intestinal microbiome and in contrast to its well-appreciated microbiome-dependent protective role in intestinal colitis and tumorigenesis.

Low incidence of HHV-6 reactivation in haploidentical hematopoietic stem cell transplantation with corticosteroid as graft-vs-host disease prophylaxis compared with cord blood transplantation.

BACKGROUND: Human leukocyte antigen (HLA) mismatch and the administration of immunosuppressive agents are considered risks for human herpesvirus 6 (HHV-6) reactivation after stem cell transplantation (SCT). However, the incidence of HHV-6 reactivation in HLA-mismatched related SCT remains unknown. METHODS: We monitored plasma HHV-6 DNA loads weekly using real-time quantitative polymerase chain reaction for 5 weeks after SCT and compared serum IL-6 levels in HLA-mismatched SCT groups. RESULTS: Compared with detection in all 11 umbilical cord blood transplantation (CBT) patients (100%), plasma HHV-6 DNA was detected in only 3 of 42 haplo-SCT patients (7.1%) despite the use of methylprednisolone and antithymocyte globulin as graft-vs-host disease prophylaxis and a reduced-intensity conditioning regimen, respectively. Correspondingly, serum IL-6 levels in haplo-SCT patients were significantly lower than those in CBT patients. No HHV-6-associated encephalitis developed in either groups. CONCLUSIONS: Neither HLA disparity nor the use of methylprednisolone and antithymocyte globulin were risk factors for HHV-6 reactivation in our haplo-SCT patients. Rather than increasing risk, the administration of immunosuppressive agents potentially prevented HHV-6 reactivation after haplo-SCT by suppressing IL-6 production.

Mitochondrial Deacetylase SIRT3 Plays an Important Role in Donor T Cell Responses after Experimental Allogeneic Hematopoietic Transplantation.

Allogeneic hematopoietic cell transplantation (allo-HCT) through its graft-versus-tumor (GVT) effects is a curative therapy against many hematological malignancies. However, GVT is linked to harmful graft-versus-host disease (GVHD) after allo-HCT. Both GVT and GVHD require allogeneic T cell responses, which is an energetically costly process that causes oxidative stress. Sirtuin 3 (SIRT3), a mitochondrial histone deacetylase (HDAC), plays an important role in cellular processes through inhibition of reactive oxygen species (ROS). Nonmitochondrial class of HDACs regulate T cell responses, but the role of mitochondrial HDACs, specifically SIRT3, on donor T cell responses after allo-HCT remains unknown. In this study, we report that SIRT3-deficient (SIRT3-/-) donor T cells cause reduced GVHD severity in multiple clinically relevant murine models. The GVHD protective effect of allogeneic SIRT3-/- T cells was associated with a reduction in their activation, reduced CXCR3 expression, and no significant impact on cytokine secretion or cytotoxic functions. Intriguingly, the GVHD protective effect of SIRT3-/- T cells was associated with a reduction in ROS production, which is contrary to the effect of SIRT3 deficiency on ROS production in other cells/tissues and likely a consequence of their deficient activation. Notably, the reduction in GVHD in the gastrointestinal tract was not associated with a substantial reduction in the GVT effect. Collectively, these data reveal that SIRT3 activity promotes allogeneic donor T cell responses and ROS production without altering T cell cytokine or cytolytic functions and identify SIRT3 as a novel target on donor T cells to improve outcomes after allo-HCT.

STAT3 Expression in Host Myeloid Cells Controls Graft-versus-Host Disease Severity.

Professional antigen-presenting cells (APCs) are important modulators of acute graft-versus-host disease (GVHD). Although dendritic cells (DCs) are the most potent APC subset, other myeloid cells, especially macrophages (MFs) and neutrophils, recently have been shown to play a role in the severity of GVHD. The critical molecular mechanisms that determine the functions of myeloid cells in GVHD are unclear, however. Signal transducer and activator of transcription 3 (STAT3) is a master transcription factor that plays a crucial role in regulating immunity, but its role in MF biology and in acute GVHD remains unknown. To determine the impact of myeloid cell-specific expression of STAT3 on the severity of acute GVHD, we used myeloid cell-specific STAT3-deficient LysM-Cre/STAT3fl/- animals as recipients and donors in well-characterized experimental models of acute GVHD. We found that reduced expression of STAT3 in myeloid cells from the hosts, but not the donors, increased inflammation, increased donor T cell activation, and exacerbated GVHD. Our data demonstrate that STAT3 in host myeloid cells, such as MFs, dampens acute GVHD.

Siglec-G represses DAMP-mediated effects on T cells.

The role of negative regulators or suppressors of the damage-associated molecular pattern-mediated (DAMP-mediated) stimulation of innate immune responses is being increasingly appreciated. However, the presence and function of suppressors of DAMP-mediated effects on T cells, and whether they can be targeted to mitigate T cell-dependent immunopathology remain unknown. Sialic acid-binding immunoglobulin-like lectin G (Siglec-G) is a negative regulator of DAMP-mediated responses in innate immune cells, but its T cell-autonomous role is unknown. Utilizing loss-of-function-based (genetic knockout) and gain-of-function-based (agonist) approaches, we demonstrate that in the presence of certain DAMPs, Siglec-G suppressed in vitro and in vivo T cell responses. We also demonstrate that its T cell-autonomous role is critical for modulating the severity of the T cell-mediated immunopathology, graft-versus-host disease (GVHD). Enhancing the Siglec-G signaling in donor T cells with its agonist, a CD24Fc fusion protein, ameliorated GVHD while preserving sufficient graft-versus-tumor (GVT) effects in vivo. Collectively, these data demonstrate that Siglec-G is a potentially novel negative regulator of T cell responses, which can be targeted to mitigate GVHD.

IAPs protect host target tissues from graft-versus-host disease in mice.

Inhibitors of apoptosis proteins (IAPs) regulate apoptosis, but little is known about the role of IAPs in the regulation of immunity. Development of IAP inhibition by second mitochondria-derived activator of caspase (SMAC) mimetics is emerging as a novel therapeutic strategy to treat malignancies. We explored the role of IAPs in allogeneic immunity with 2 distinct yet complementary strategies, namely, chemical and genetic approaches, in clinically relevant models of experimental bone marrow transplantation (BMT). The small-molecule pan-IAP inhibitor SMAC mimetic AT-406 aggravated gastrointestinal graft-versus-host disease (GVHD) in multiple models. The role of specific IAPs in various host and donor cellular compartments was explored by utilizing X-linked IAP (XIAP)- and cellular IAP (cIAP)-deficient animals as donors or recipients. Donor T cells from C57BL/6 cIAP1-/- or XIAP-/- animals demonstrated equivalent GVHD severity and allogeneic responses, both in vivo and in vitro, when compared with B6 wild-type (B6-WT) T cells. By contrast, when used as recipient animals, both XIAP-/- and cIAP1-/- animals demonstrated increased mortality from GVHD when compared with B6-WT animals. BM chimera studies revealed that cIAP and XIAP deficiency in host nonhematopoietic target cells, but not in host hematopoietic-derived cells, is critical for exacerbation of GVHD. Intestinal epithelial cells from IAP-deficient animals showed reduced levels of antiapoptotic proteins as well as autophagy-related protein LC3 after allogeneic BMT. Collectively, our data highlight a novel immune cell-independent but target tissue-intrinsic role for IAPs in the regulation of gastrointestinal damage from GVHD.

Spousal hematopoietic stem cell transplantation.

We report a pilot series of five patients who received stem cell transplantation (SCT) from a spouse for post-transplant relapse or rejection. The inclusion criterion regarding HLA disparities was three or fewer antigen mismatches in the graft-versus-host direction at the HLA-A, B, and DR loci. Four patients received spousal SCT as a third transplant attempt after post-transplant relapse and one as rescue for graft rejection. The reduced intensity conditioning (RIC) regimen consisted of fludarabine, melphalan, and anti-thymocyte globulin (ATG) with 3 Gy of total body irradiation (TBI) for relapse cases and ATG plus 4 Gy of TBI for the rejection case. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus, methylprednisolone, and mycophenolate mofetil. Peripheral blood stem cells were transplanted. Granulocyte engraftment was achieved in all cases between days 9 and 11 (median, 10) with complete spousal chimerism. In three of the five patients, no acute GVHD was observed, while one case developed grade III GVHD and one case grade IV. All four patients evaluable for the anti-leukemic effect achieved complete remission; however, all relapsed between 106 and 334 day post-transplant, and died between days 152 and 548. We suggest that spousal SCT can be performed as a repetitive SCT using a RIC regimen with low-dose ATG and steroid-containing GVHD prophylaxis.

Allogeneic stem cell transplantation for X-linked agammaglobulinemia using reduced intensity conditioning as a model of the reconstitution of humoral immunity.

BACKGROUND: We herein report the first case of X-linked agammaglobulinemia (XLA) that underwent allogeneic stem cell transplantation using reduced intensity conditioning (RIC). We chronologically observed the reconstitution of humoral immunity in this case. CASE PRESENTATION: The patient was a 28-year-old Japanese male with XLA who previously had life-threatening infectious episodes and was referred for the possible indication of allogeneic stem cell transplantation. After a thorough discussion within specialists from different backgrounds, we decided to perform allogeneic peripheral stem cell transplantation from his HLA-identical elder brother. Due to the non-malignant nature of XLA, we selected RIC consisting of fludarabine, cyclophosphamide, anti-thymocyte globulin, and 3 Gy of total body irradiation. Neutrophil engraftment was achieved on day 11 with complete donor chimerism. No major complications, except for stage 1 skin graft-versus-host disease, were observed. The patient was discharged on day 75 and has been followed as an outpatient without any infectious episodes for more than 500 days. CONCLUSIONS: Regarding immune reconstitution, CD19(+) cells, IgA, and IgM, which were undetectable before allogeneic stem cell transplantation (allo-SCT), started to increase in number 10 days after allo-SCT and continued to increase for more than 1 year. Anti-B antibodies appeared as early as day 10. Total IgG levels decreased after the discontinuation of IgG replacement and spontaneously recovered after day 350. However, most anti-viral IgG titers, except EB virus-virus capsid antigen IgG, disappeared after the discontinuation of IgG replacement. A seasonal vaccination to influenza was performed on day 148, with neither anti-influenza type A nor type B being positive after the vaccination. The transient transfer of allergic immunity to orchard grass was observed. Similar Bruton's tyrosine kinase (BTK) expression levels in monocytes and B-cells were observed between the patient and healthy control. B-cells in the peripheral blood (PB) of the patient on day 279 showed sufficient proliferation after a CD40L and IL-21 or CD40L and CpG stimulation. Effective immunoglobulin production and class switching were also observed after a CD40L and IL-21 or CpG stimulation. Signal joint kappa-deleting recombination excision circles (sjKRECs) became positive 16 days post-SCT, increased to 6300 copies/µg DNA at 42 days, and were maintained at a high level thereafter. The recovery of T-cell receptor excision circles (TRECs) was slow, but became detectable 1 year post-hematopoietic stem cell transplantation (HSCT).

Host Foxp3+CD4+ Regulatory T Cells Act as a Negative Regulator of Dendritic Cells in the Peritransplantation Period.

Host Foxp3+CD4+ regulatory T cells (Tregs) have been shown to suppress graft-versus-host disease (GVHD) in experimental bone marrow transplantation (BMT) models; however, the detailed mechanism is unknown. To address this issue, we established a murine MHC-haploidentical BMT model (BDF1 (H-2b/d) → B6C3F1 (H-2b/k)), in which transplantation following conditioning with high-dose (13 Gy) or low-dose (5 Gy) total body irradiation corresponds to myeloablative stem cell transplantation (MAST) or reduced-intensity stem cell transplantation (RIST) BMT. All MAST recipients died of GVHD within 70 d, whereas RIST recipients developed almost no GVHD and survived for at least 3 mo. In this BMT model, we investigated the kinetics of immune cells in the mesenteric lymph nodes because GVHD was most prominent in the intestines. Host Tregs that survived after total body irradiation could proliferate transiently by day 4. Comparing the kinetics of immune cells among MAST, RIST, and anti-CD25 mAb-treated RIST, we found that the transiently surviving host Tregs were fully functional, closely contacted with host dendritic cells (DCs), and significantly restrained the maturation (CD80 and CD86 expression) of DCs in a dose-dependent manner. There was a positive correlation between the ratio of DCs to host Tregs and the extent of maturation of DCs. Host Tregs suppressed alloresponse mainly by contact inhibition. Host Tregs are already active in lymph nodes before transplantation and restrain the maturation of host DCs, thereby dampening the ability of DCs to activate allogeneic donor T cells and consequently reducing the magnitude of graft-versus-host reaction. Thus, host Tregs are negative regulators of host DCs that act in the peritransplantation period.