Leukocyte Transfusions Research Articles

Inflammation Control and Immunotherapeutic Strategies in Comprehensive Cancer Treatment.

Tumor growth and expansion are determined by the immunological tumor microenvironment (TME). Typically, early tumorigenic stages are characterized by the immune system not responding or weakly responding to the tumor. However, subsequent tumorigenic stages witness the tumor promoting its growth and metastasis by stimulating tumor-protective (pro-tumor) inflammation to suppress anti-tumor immune responses. Here, we propose the pivotal role of inflammation control in a successful anti-cancer immunotherapy strategy, implying that available and novel immunotherapeutic modalities such as inflammation modulation, antibody (Ab)-based immunostimulation, drug-mediated immunomodulation, cancer vaccination as well as adoptive cell immunotherapy and donor leucocyte transfusion could be applied in cancer patients in a synergistic manner to amplify each other's clinical effects and achieve robust anti-tumor immune reactivity. In addition, the anti-tumor effects of immunotherapy could be enhanced by thermal and/or oxygen therapy. Herein, combined immune-based therapy could prove to be beneficial for patients with advanced cancers, as aiming to provide long-term tumor cell/mass dormancy by restraining compensatory proliferation of surviving cancer cells observed after traditional anti-cancer interventions such as surgery, radiotherapy, and metronomic (low-dose) chemotherapy. We propose the Inflammatory Prognostic Score based on the blood levels of C-reactive protein and lactate dehydrogenase as well as the neutrophil-to-lymphocyte ratio to effectively monitor the effectiveness of comprehensive anti-cancer treatment.

Erythroid homograft following leukocyte transfusion in a patient with acute leukemia. II. Serologic and immunochemical studies.

THE APPEARANCE of female Philadelphia (Ph1) chromosomes in a male patient of blood group O who had received a transfusion of leukocyte-rich plasma from a female of blood group A with chronic myelogenous leukemia (CML), made it possible to conduct a study of blood groups during induction, growth and rejection of a hematopoietic graft. The recipient was being treated for acute lymphocytic leukemia. Observations were made on red cell, white cell and platelet antigens and their corresponding antibodies as well as the serum gamma globulin (Gm and Inv) groups. Only the data on red cell systems were conclusive. After the recipient showed doubling of his red cell mass, 85 per cent of these red cells were of the donor group A. Despite the presence of group A cells some free anti-A agglutinin was present throughout most of the two month graft life. Anti-B agglutinins appeared in very high titer. When the graft was rejected, immune anti-A hemolysin appeared and the cells of donor group A were rapidly destroyed.

The effect of different methods of leucoreduction on plasma coagulation factors.

Removal of leucocytes from blood products, namely leucoreduction, improves the safety of blood transfusion by reducing adverse events associated with the incidental transfusion of leucocytes. Coagulation factors might be compromised during leucoreduction because of exposure of plasma to a variety of filter materials. The aim of the current study was to assess the effect of different methods of prestorage leucofiltration (apheresis and whole blood filters) on prothrombin time, international normalized ratio, partial thromboplastin time and factors V and VIII. There was a significant prolongation of prothrombin time as well as elevation of international normalized ratio in plasma after leucoreduction (14.5 ± 0.7 s vs. 13.9 ± 0.7 s, P = 0.008 and 1.14 ± 0.07 vs. 1.09 ± 0.07, P = 0.005, respectively). Also, there was a statistically significant prolongation of activated partial thromboplastin time in nonleucoreduced plasma (55.6 ± 9.9 s vs. 43.2 ± 12.8 s, P = 0.001). There was no significant filtration effect on factors V and VIII levels. Furthermore, there was no significant difference in factors V and VIII levels between plasma filtered by inline whole blood filters and apheresis machine. Leucodepleted plasma originating from both inline whole blood filter and apheresis machine maintained satisfactory levels of factors V and VIII.

Posaconazole-Loaded Leukocytes as a Novel Treatment Strategy Targeting Invasive Pulmonary Aspergillosis.

Impaired delivery of antifungals to hyphae within necrotic lesions is thought to contribute to therapeutic failure in invasive pulmonary aspergillosis (IPA). We hypothesized that transfusion of leukocytes loaded ex vivo with the lipophilic antifungal posaconazole could improve delivery of antifungals to the sites of established infection and improve outcome in experimental IPA. The HL-60 leukemia cell line was differentiated to a neutrophil-like phenotype (differentiated HL-60 [dHL-60] cells) and then exposed to a range of posaconazole concentrations. The functional capacity and antifungal activity of these cells were assessed in vitro and in a mouse model of IPA. Posaconazole levels in dHL-60 cells were 265-fold greater than the exposure concentration. Posaconazole-loaded cells were viable and maintained their capacity to undergo active chemotaxis. Contact-dependent transfer of posaconazole from dHL-60 cells to hyphae was observed in vitro, resulting in decreased fungal viability. In a neutropenic mouse model of IPA, treatment with posaconazole-loaded dHL-60 cells resulted in significantly reduced fungal burden in comparison to treatment with dHL-60 cells alone. Posaconazole accumulates at high concentrations in dHL-60 cells and increases their antifungal activity in vitro and in vivo. These findings suggest that posaconazole-loading of leukocytes may hold promise for the therapy of IPA.

Platelet-mediated adhesion facilitates leukocyte sequestration in hypoxia-reoxygenated microvessels.

Leukocyte transendothelial migration and sequestration are two distinct outcomes following leukocyte adhesion to endothelium during ischemia-reperfusion injury, in which platelets may play a pivotal role. In the present study, we established an in vitro hypoxia-reoxygenation model to mimic ischemia-reperfusion injury and found platelet pre-incubation significantly increased leukocyte adhesion to endothelial cells after hyoxia-reoxygenation (over 67%). Blockade of endothelial-cell-expressed adhesion molecules inhibited leukocyte direct adhesion to endothelial cells, while platelet-mediated leukocyte adhesion was suppressed by blockade of platelet-expressed adhesion molecules. Further experiments revealed platelets acted as a bridge to mediate leukocyte adhesion, and platelet-mediated adhesion was the predominant pattern in the presence of platelets. However, platelet pre-incubation significantly suppressed leukocyte transendothelial migration after hypoxia-reoxygenation (over 31%), which could be aggravated by blockade of endothelial-cell-expressed adhesion molecules, but alleviated by blockade of platelet- expressed adhesion molecules. This would indicate that platelet-mediated adhesion disrupted leukocyte transendothelial migration. An in vivo mesenteric ischemia-reperfusion model demonstrated leukocyte transfusion alone caused mild leukocyte adhesion to reperfused vessels and subsequent leukocyte infiltration, while simultaneous leukocyte and platelet transfusion led to massive leukocyte adhesion and sequestration within reperfused microvessels. Our studies revealed platelets enhanced leukocyte adhesion to endothelial cells, but suppressed leukocyte transendothelial migration. Overall, this leads to leukocyte sequestration in hypoxia-reoxygenated microvessels.

Dose response kinetics of CD8 lymphocytes from young animals transfused into old animals and challenged with influenza

Transfusion of autologous leukocytes after prolonged storage has been proposed as a means of rejuvenating the immune system of older individuals. The rationale for this approach is that age related immune decline is associated with a diminished pool of naïve T cells following atrophy of the thymus and reduction in thymic output. The presence of high levels of naïve T cells within the blood of young individuals could provide a boost to the immune system of an older “self” through a rejuvenation of the naïve T cell pool. However what remains unresolved is whether the cells could be incorporated effectively into the T cell pool of the host and whether effectors could be generated. Using CD45 congenic mice in our experiments we show that the transfusion of young donor cells into older congenic host animals leads to their successful incorporation into the peripheral T cell pool. When the recipients were challenged with influenza virus, specific effector CD8 cells were generated which were of both host and donor origin. We found no relationship between the number of responder cells of donor origin at the time of assay and the number of cells injected.

Molecular and functional characterization of human bone marrow adipocytes

Adipocytes are a cell population largely located in the human bone marrow cavity. In this specific microenvironment where adipocytes can interact with a variety of different cells, the role of fat is mainly unknown. To our knowledge, this report is the first to characterize mature adipocytes isolated from human bone marrow (BM-A) molecularly and functionally to better understand their roles into the hematopoietic microenvironment. Healthy BM-A were isolated after collagenase digestion and filtration. We studied the morphology of BM-A, their gene expression and immunophenotypic profile and their functional ability in the hematopoietic microenvironment, comparing them with adipocytes derived from adipose tissue (AT-A). BM-A showed a unilocular lipid morphology similar to AT-A and did not lose their morphology in culture; they showed a comparable pattern of stem cell-surface antigens to AT-A. In line with these observations, molecular data showed that BM-A expressed some embryonic stem cells genes, such as Oct4, KLf4, c-myc, Gata4, Tbx1, and Sox17, whereas they did not express the stem cell markers Sox2 and Nanog. Moreover, BM-A had long telomeres that were similar to bone marrow mesenchymal stem cells. Notably, BM-A supported the survival and differentiation of hematopoietic stem cells in long-term cultures. These results showed that BM-A are stromal cells with a gene expression pattern that distinguished them from AT-A. BM-A showed stem cell properties through their hematopoietic supporting function, which was certainly linked to their role in the maintenance of the bone marrow microenvironment. Depending on specific demands, BM-A may acquire different functions based on their local environment.

Leukocyte Transfusion and the Development of the Continuous-Flow Blood Cell Separator

The treatment of anemia and thrombocytopenia with allogeneic cell transfusions is an effective and well-developed technology. However, leukocyte replacement transfusion has been frustrated by the physiology of the leukocytes. To achieve effective leukocyte replacement, the continuous-flow centrifugal blood cell separator was developed, and it soon proved to be an important instrument for separation, collection, and transfusion of all the components of the blood. Thus, the continuous-flow centrifugal blood cell separator has become an important instrument in the science of blood collection and transfusion.

Minimal Residual Disease following Allogeneic Hematopoietic Stem Cell Transplantation

Minimal residual disease (MRD), both before and after transplantation, is a clinically important yet relatively poorly defined aspect of allogeneic hematopoietic stem cell transplantation (alloHSCT). The clinical relevance of MRD in the context of alloHSCT has been demonstrated by its association with the development of clinical relapse. However, with the possible exception of chronic myeloid leukemia (CML), the specific techniques, timing, frequency, and clinical utility, relative to improvement in patient outcomes, for monitoring MRD in the setting of alloHSCT has yet to be clearly defined. A concise overview of monitoring techniques for detecting MRD, as well as treatment strategies and biological and clinical research initiatives for MRD suggested by the National Cancer Institute First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation, is covered in this article.

Leukemia Lineage-Specific Chimerism Analysis and Molecular Monitoring Improve Outcome of Donor Lymphocyte Infusions

A retrospective analysis was performed of 118 patients with hematologic malignancies who received donor lymphocyte infusions (DLIs) after allogeneic stem cell transplantation (ASCT). Treatment was either given because of hematologic relapse (n = 44), molecular/cytogenetic relapse (n = 52), or other causes (n = 22). Molecular relapse was in most cases based on leukemia lineage-specific chimerism analysis. Patients with acute leukemia and myelodysplastic syndrome showed a 3-year survival of 42% if DLI treatment was given because ofmolecular relapse, compared to 16% in hematologic relapse (P < .006). In multivariate analysis, there was a correlation between response to DLI and nonhematologic relapse (risk ratio [RR] 3.36, P = .001), chronic graft-versus-host disease (cGVHD) (RR = 1.51, P = .005), and late relapse (RR = 2.06, P = .017). The overall incidences of acute GVHD (aGVHD) grades I-II and grades III-IV aGVHD were 33% and 8.5%, respectively. Probability of cGVHD was 33%. The development of aGVHD or cGVHD did not significantly influence the response of DLI in patients with molecular/cytogenetic relapse. However, the development of cGVHD was significantly associated with a better response in patients with hematologic relapse because only 4 of 29 patients without cGVHD responded compared to 7 of 12 with cGVHD (P = .007). The development of cGVHD increased significantly if DLI was given >12 months after ASCT (46% versus 27%, P = .04). In contrast, time between ASCT and start of DLI treatment had no significant influence on the risk of developing aGVHD. To conclude, monitoring of leukemia lineage-specific chimerism is of utmost importance for DLI response after ASCT.

Transfusion of Ipscs-Derived Leukocytes to Kill Cancer

Here we propose that the rejuvenation of leukocytes with iPSC technology in vitro and transfusion of cancer cellresistant white blood cells back to human body provide a prospective therapy for cancer patients.

Transferable Cardiac Allograft Acceptance Induced by Transfusion of Donor B Cells With Impaired Inducible Costimulator/B7h Allorecognition

Objective Donor-specific transfusion (DST) of leukocytes with an impaired costimulatory signal has been proven to be an effective way to improve allograft survival. Inducible costimulator (ICOS) has been shown to play a crucial role in acute and chronic allograft rejection. To test the role of ICOS signaling during DST, we employed ICOS-Fc-targeted B cells as antigen of DST to challenge the allogeneic engraftment in vivo. Materials and Methods A murine cardiac allograft model was employed using BALB/c donors and C57BL/6 recipients, while various transfusions were performed according to treatment protocols. Results Allograft survival was prolonged by infusion of ICOS-Fc-targeted B cells; however, allograft acceptance could not be achieved unless additional systemic injections of ICOS-Fc were given. Adoptive transfer of splenic CD4 + but not CD4 +CD25 − subsets from long-term allograft survival (LTAS) mice to lightly irradiated naive recipients resulted in subsequent BALB/c allograft acceptance without additional immunosuppression. Conclusions ICOS/B7h signaling during direct allorecognition played an important role in prolonging allograft survival, and an allograft acceptance can be established by DST with complete blockade of ICOS/B7h in both direct and indirect allorecognition. Interestingly, this allograft acceptance was transferable and maintained at least partly by the immune regulation of CD4 +CD25 + T cells. These findings may help to design a potential therapeutic treatment to prevent allograft rejection by DST in combination with ICOS/B7h blockade.

本邦における同種骨髄移植後の白血病再発例に対するdonor leukocyte transfusion(DLT)の治療効果

本邦における同種骨髄移植後の白血病再発例に対するdonor leukocyte transfusion(DLT)の治療効果

Leukocyte urokinase plasminogen activator receptor and PSGL1 play a role in endogenous arterial fibrinolysis

Fibrin is an integral component of arterial thrombi. Using a mouse model of arteriolar thrombosis, high-speed fluorescence microscopy reveals that, within minutes, the fibrin content of thrombi rapidly increases and then decreases. The decrease in fibrin coincides with leukocyte binding to the thrombi, a process mediated by the interaction of leukocyte P-selectin glycoprotein ligand-1 (PSGL-1) with P-selectin on the surface of activated platelets. Because leukocytes possess urokinase-type plasminogen activator (uPA) activity, we used mice deficient in uPA or the uPA receptor (uPAR) to explore the contribution of leukocyte-associated uPA to the loss of fibrin from these thrombi. Fibrin loss in both uPA-deficient mice and uPAR-deficient mice was reduced compared with that in wild-type controls. Transfusion of leukocytes from wild-type mice into uPAR-deficient mice restored fibrin loss to levels similar to that in wild-type mice. In contrast, transfusion of leukocytes from mice deficient in uPAR or PSGL-1 did not enhance fibrin loss. Thus, fibrin loss from microarteriolar thrombi is mediated, at least in part, by leukocyte-associated uPA in a process that requires leukocyte uPAR and PSGL-1.

Impact of Intraportal Donor-Specific Leukocyte Transfusion for Adult ABO-Incompatible Liver Transplantation

Introduction We have reported that repeated donor-specific leukocyte transfusions (DSLT) via the portal vein allow rapid reduction of immunosuppressants and decrease the occurrence of acute cellular rejection. Herein, we examined the immunological benefits of DSLT in adult ABO-incompatible living donor liver transplantation (LDLT). Materials and Methods Ten adult patients (MELD score, 19.4 ± 7.3; range, 12–29) underwent LDLT from ABO-incompatible donors from August 2003 to November 2007. The antirejection therapy included multiple perioperative plasmaphereses, splenectomy, and quadruple immunosuppression. In addition to these conventional approaches, we performed 4 intraportal administrations of DSLT after transplantation. Results There was no humoral rejection in any patient. Two patients experienced mild cellular rejection requiring steroid pulse therapy. Both donor-specific immunoglobulin (Ig)M and IgG A/B antibodies in all patients decreased following transplantation by 16 fold. By flow cytometry, donor type of CD56+NK T cells existed in the liver graft showing macrochimerism at 1 month after liver transplantation. Furthermore, interleukin (IL)-10 production of Th2 type cytokines was up-regulated after transplantation. Three patients died of sepsis and infection. The 5-year survival rate was 70% by the Kaplan-Meier method. Conclusion Adult ABO-incompatible liver transplantation can be performed with acceptable patient and graft survival rates with a low risk of antibody-mediated rejection using intraportal administration of DSLT. Donor type CD56+NK T cells may induce tolerance by a veto or an anti-idiotype network mechanism.

Ahmedabad tolerance induction protocol and chronic renal allograft dysfunction: pathologic observations and clinical implications

BackgroundChronic Renal Allograft Dysfunction (CRAD) is responsible for a large number of graft failures. We have abrogated acute T-cell rejections using Ahmedabad Tolerance Induction Protocol (ATIP) with hematopoietic stem cell transplantation (HSCT) under non-myeloablative conditioning pre-transplant. However B-cell mediated rejections and CRAD continue to haunt us. We carried out retrospective analysis of renal allograft biopsies performed in the last 4 years to evaluate the effect of ATIP on CRAD.Materials and methodsBiopsies diagnosed as per modified Banff criteria belonged to 2 groups: ATIP under low dose immunosuppression of cyclosporine/Azathioprine/Mycofenolate mofetil+ Prednisolone, subjected to donor leucocyte transfusion, anti-T/B cell antibodies, low dose target specific irradiation, cyclophosphamide, cyclosporin followed by HSCT pre-transplant; controls who opted out of ATIP were transplanted under standard triple drug immunosuppression. Demographics of both groups were comparable.ResultsIncidence of chronic changes was higher in controls (17.5%) vs. 10.98% in ATIP over a mean follow up of 151.9 months in the former and 130.9 months in the latter. Proteinuria and hypertension were higher in controls (48.4%) vs. ATIP (32.7%) with chronic transplant glomerulopathy, focal global sclerosis in 67.7% in controls vs. 46.7% in ATIP, acute on chronic T/B cell rejection in 51.6% controls vs. 28.1% ATIP, with peritubular capillary C4d deposits in 19.4% controls vs. 1.9% ATIP biopsies. Acute on chronic calcineurin inhibitor toxicity was higher in ATIP (71.9%) vs. 48.4% in controls.ConclusionChronic immune injury was less with ATIP vs controls as compared to a higher incidence of chronic calcineurin inhibitor toxicity in the former.

ORIGINAL ARTICLE: Cell‐Surface CD200 May Predict Efficacy of Paternal Mononuclear Leukocyte Immunotherapy in Treatment of Human Recurrent Pregnancy Loss

Problem The allogeneic leukocytes in transfused blood can modulate the recipient’s immune system so as to induce TGF‐β‐producing suppressor cells, and the cell‐surface CD200 tolerance‐signaling molecule on mononuclear dendritic cells is required for this effect. A subset of couples with unexplained recurrent pregnancy loss appears to benefit from transfusion of allogeneic paternal blood leukocytes (LIT), and considerable effort has been devoted to characterizing those who may benefit. Some data has been accumulated for LIT as sole therapy in patients with classical spontaneous abortions with respect to dose–response, duration of protection, need for boosting, excluding patients with autoimmunity, and inefficacy of paternal mononuclear cells stored at 4°C overnight before use which causes loss of cell‐surface CD200. Recent data emphasize an important role of expression of the CD200 tolerance‐signaling molecule on cells used to prevent abortions both in mice and humans.Method of study An observational study of outcome as a function of the number of CD200+ paternal mononuclear cells was performed. Fourteen patients constituted the pilot group. Patients with autoimmunity who had failed inspite of treatment with IVIG + Heparin + Aspirin ± Prednisone were allowed to have paternal mononuclear cells added to their therapy. CD200 on purified paternal blood mononuclear cells was measured by flow cytometry.Results The number of CD200+ cells administered was significantly greater in women achieving pregnancy (39.2 × 106 versus 20.8 × 106, P &lt; 0.025) and in those who achieved a live birth (50.2 × 106 versus 20.8 × 106, P &lt; 0.005) compared to those who did not achieve pregnancy, and % of paternal cells that were CD200+ was greater (11–12.5% versus 5.6%, P &lt; 0.01). Amongst those achieving pregnancy which failed, the CD200+ cell dose was not significantly different from the non‐pregnant group (30.5 × 106 versus 20.8 × 106).Conclusion The number of CD200+ paternal mononuclear leukocytes may be an important determinant of subsequent reproductive outcome in a subset of patients. A lower % CD200+ cell number may also reflect hitherto unappreciated paternal factors bearing on reproductive success. It is feasible to recruit women to enter observational studies and to obtain useful data as a foundation for further studies. More complete patient characterization in a larger study is needed.

Adult ABO-Incompatible Liver Transplantation by Intraportal Transfusion of Donor-Specific Antigen: A Case Report

A 55-year-old-woman suffering from fluminant hepatitis owing to autoimmune hepatitis underwent ABO-incompatible liver transplantation (LRLD) of blood type A to B. In this study, we investigated whether a new immunosuppressive strategy by intraportal transfusion of donor-specific leukocytes (DSLT) separated from whole blood would yield immunological benefit in adult ABO-LRLD. The operative course was uneventful; she was discharged at 46 days postoperatively without humoral or cellular rejection. On immunologic analysis, 54.6% intrahepatic macrochimerism of donor type CD56 + T cells was recognized at 1 month after transplantation. The interleukin-10 Th2 cytokine level was increased on postoperative day 1. Adult ABO-incompatible liver transplantation can be performed with acceptable patient and graft survival rates with a low risk of antibody-mediated rejection with our strategy of immunosuppression by intraportal administration of DSLT. Donor type CD56 + NKT cells may induce tolerance by a veto mechanism and/or an anti-idiotype network. ABO-incompatible liver transplantation may be improved by this strategy.

Living Related Pancreas Transplantation Alone With Enteric Drainage in Japan: Case Report

In this study, we report a living donor partial pancreas transplantation using intraportal donor-specific leukocyte transfusion (DSLT). The recipient was a 38-year-old woman who had type I diabetes mellitus for 17 years. Hypoglycemia occurred 2 or 3 times per week. Her hemoglobin A 1c level was 9.0%, and she required 70 U of insulin almost every day. The donor was her 64-year-old father. The steroid-minimized immunosuppressive protocol included 1.5mg of thymoglobulin administered with a steroid bolus on days 0, 4, and 7 postoperatively. Steroids were never prescribed thereafter. Postoperative maintenance therapy included tacrolimus (FK506) and mycophenolate mofetil. In addition to these conventional approarches, we administered intraportal DSLT on days 0, 1, 4, and 7 after transplantation. The donor-specific leukocytes (40mL) had been separated from donor whole blood using an apheresis filter (Cellsorba EX; Asahi Kasei medical Co, Ltd, Tokyo, Japan). In the recipient operation, a segmental pancreas graft was transplanted into the right iliac cavity with enteric drainage with a pancreatic duct stent. Operation time was 6 hours. The postoperative course was uneventful. The patient was discharged on day 15 after transplantation. There was no acute rejection for six months after transplantation. The hemoglobin A 1c level recovered to 5.1% with 6 U of insulin per day. At immunologic analysis, only interleukine-10 cytokine production was elevated at 7 days after transplantation. At flow cytometry cross-match analysis, the immunoglobulin M antibody decreased from day 7 after transplantation. We conclude that intraportal DSLT may be an effective adjunct to a steroid-free regimen.

Leukocyte transfusions revisited: Stem cell graft stimulation in graft failure

The aim was to evaluate the role of leukocyte transfusions (LTX) in relation to graft function during prolonged neutropenia after stem cell transplantation (SCT). In 1989-2005, 22 SCT patients have received LTX in our unit. In all patients severe infection with profound neutropenia (<0.2 x 10(9)/L) preceded LTX. 13/22 had multi-organ failure or thrombotic microangiopathy. Irradiated leukocytes from pooled random donor products at 1.0 x 10(10) leukocytes/m(2)/day for a minimum of 3 days were used. Myeloid recovery and clinical benefit were analyzed. Engraftment defined as an absolute neutrophil count (ANC) of >0.5 x 10(9)/L on three consecutive days was observed in 15/22 (68%) patients at median of 6 (range 2-25) days after LTX, and sustained engraftment (ANC of >0.5 x 10(9)/L for 4 weeks) in 11/22 (50%) patients. Clinical benefit was observed in 6/22 (27%) patients with a prolonged antecedent neutropenia, who still demonstrated rapid sustained engraftment after LTX. Ongoing thrombotic microangiopathy was associated with persistent graft failure. LTX from random donors was associated with a rapid recovery of myeloid function in severely ill SCT patients. We speculate that allostimulation by LTX may have a role.