Analysis of tissues following mesenchymal stromal cell therapy in humans indicates limited long-term engraftment and no ectopic tissue formation.

Mesenchymal stromal cells (MSCs) are explored as a novel treatment for a variety of medical conditions. Their fate after infusion is unclear, and long-term safety regarding malignant transformation and ectopic tissue formation has not been addressed in patients. We examined autopsy material from 18 patients who had received human leukocyte antigen (HLA)-mismatched MSCs, and 108 tissue samples from 15 patients were examined by PCR. No signs of ectopic tissue formation or malignant tumors of MSC-donor origin were found on macroscopic or histological examination. MSC donor DNA was detected in one or several tissues including lungs, lymph nodes, and intestine in eight patients at levels from 1/100 to <1/1,000. Detection of MSC donor DNA was negatively correlated with time from infusion to sample collection, as DNA was detected from nine of 13 MSC infusions given within 50 days before sampling but from only two of eight infusions given earlier. There was no correlation between MSC engraftment and treatment response. We conclude that MSCs appear to mediate their function through a "hit and run" mechanism. The lack of sustained engraftment limits the long-term risks of MSC therapy.

Characterization of long-term mixed donor-donor chimerism after double cord blood transplantation.

Double cord blood transplantation (DCBT) with two matched or partially matched cord blood units has been implemented successfully to circumvent the limitations of graft cell dose associated with single CBT. After DCBT, sustained haematopoiesis is derived almost exclusively from only one of the donated units. None the less, we previously observed two of six evaluable DCBT patients still having mixed donor-donor chimerism at 28 and 45 months post-transplantation, respectively. In the present study we utilize flow cytometry techniques to perform the first thorough analysis of phenotype and functionality of cord blood units in patients with mixed donor-donor chimerism. Our results suggest that the two stable cord blood units are different phenotypically and functionally: one unit shows more naive T cells, lower T cell cytokine production and higher frequencies of natural killer cells, the other shows higher frequencies of well-differentiated and functional lymphocytes. Additionally, in comparison with control patients having a single prevailing cord blood unit, the patients with donor-donor chimerism exhibit less overall T cell cytokine production and a smaller fraction of memory T cells. Furthermore, our results indicate that human leucocyte antigen-C match of donor units may partly explain the development of a donor-donor mixed chimerism.

Endometrial endothelial cells are derived from donor stem cells in a bone marrow transplant recipient.

BACKGROUND: The endometrium is a dynamic, cyclically regenerating tissue: a unique model of physiological angiogenesis in adults. However, the source of new endothelial cells (ECs) for vessel regrowth is obscure. We studied if male EC could be detected in the endometrial blood vessels of female human or mouse recipients of haematological stem cells from male donors. METHODS: Endometrial biopsies, obtained from one patient after non-myeloablative allogeneic bone marrow transplantation and two controls, were analysed by immunohistochemistry of CD34 and VEGFR2 antibodies for the immunophenotyping of EC, and FISH probes for the detection of donor cells. Chimerism was analysed using real-time PCR. The same experiment was also applied on the animal model. RESULTS: At the time of a Caesarean section in a female bone marrow transplanted patient, an average 14% of her endometrial EC were donor-derived. One year later, that figure was 10%. In contrast, none of two non-transplanted females demonstrated a mismatch in endometria at Caesarean section. In samples from female mice, harvested 40 days after a haematological stem cell transplant, a 6% average of donor-derived EC was detected. CONCLUSIONS: Bone marrow-derived endothelial progenitors contribute to the formation of new blood vessels in the endometrium.

No impact of NOD2/CARD15 on outcome after SCT.

Recent studies have pointed towards an association between certain single nucleotide polymorphisms (SNPs) in the NOD2/CARD15 gene, and negative outcome of Allo-SCT. In this study, 198 patients and their corresponding donors were analyzed retrospectively for the occurrence of NOD2/CARD15 mutations to evaluate the impact on clinical results after Allo-SCT. In all, 7.6% of the patients and 11% of the donors were heterozygous for one of three SNPs 8, 12 or 13. Contrary to earlier findings, we found no significant impact on incidence of acute GVHD or TRM following Allo-SCT. These differences in results could be due to a lower mutation frequency in the studied population and/or a lower overall incidence of severe GVHD. On the basis of these findings we conclude that a consideration to NOD2/CARD15 mutation status is not pertinent when selecting a donor for Allo-SCT at our centre.

Tissue repair using allogeneic mesenchymal stem cells for hemorrhagic cystitis, pneumomediastinum and perforated colon.

Mesenchymal stem cells (MSC) possess anti-inflammatory properties and participate in tissue repair. We used MSC to heal therapy-induced tissue toxicity. Ten consecutive patients, treated with MSC due to tissue toxicity following allogeneic hematopoietic stem cell transplantation, (ASCT) were included. Their median age was 48 (13-64) years. Seven had hemorrhagic cystitis grades 2-5, two had pneumomediastinum and one had perforated colon and peritonitis. MSC donors were mainly third-party, HLA-mismatched (n=11), HLA-haploidentical (n=3) and, in two cases, the HLA-identical ASCT sibling donors. MSC were given intravenously, the median cell dose was 1.0 (range 0.7-2)x10(6)/kg. In five patients, the severe hemorrhagic cystitis cleared after MSC infusion. Gross hematuria disappeared after median 3 (1-14) days. Two patients had reduced transfusion requirements after MSC infusion, but died of multiorgan failure. In one of them, MSC donor DNA was demonstrated in the urinary bladder. In two patients, pneumomediastinum disappeared after MSC infusions. A patient with steroid-resistant graft-versus-host disease of the gut experienced perforated diverticulitis and peritonitis that was reversed twice by MSC. MSC is a novel treatment for therapy-induced tissue toxicity.

Assessment of TREC, KREC and telomere length in long-term survivors after allogeneic HSCT: the role of GvHD and graft source and evidence for telomere homeostasis in young recipients.

Reconstitution of the adaptive immune system following allogeneic hematopoietic stem cell transplantation is crucial for beneficial outcome and is affected by several factors, such as GvHD and graft source. The impact of these factors on immune reconstitution has been thoroughly investigated during the early phase after transplantation. However, little is known about their long-term effect. Similarly, leukocyte telomere length (TL) shortening has been reported shortly after transplantation. Nevertheless, whether TL shortening continues in long-term aspect is still unsettled. Here, we assessed T-cell receptor excision circle (TREC), kappa deleting recombination excision circle (KREC) and leukocyte TL in recipients and donors several years post transplantation (median 17 years). Our analysis showed that, recipients who received bone marrow (BM) as the graft source have higher levels of both TREC and KREC. Also, chronic GvHD affected TREC levels and TL but not KREC levels. Finally, we show that recipient's TL was longer than respective donors in a group of young age recipients with high KREC levels. Our results suggest that BM can be beneficial for long-term adaptive immune recovery. We also present supporting evidence for recipient telomere homeostasis, especially in young age recipients, rather than telomere shortening.

Fludarabine-based disease-specific conditioning or conventional myeloablative conditioning in hematopoietic stem cell transplantation for treatment of non-malignant diseases.

Fludarabine-based conditioning (FBC) was given to 24 patients and conventional myeloablative conditioning (MC) to 33 patients, most children, before hematopoietic stem cell transplantation (HSCT) for non-malignant diseases. The donors were human leukocyte antigen (HLA)-A, -B, -DRbeta1-identical related (33%) or unrelated (67%). In the FBC group, two grafts failed versus three in the MC group; all were successfully regrafted. Fever was more common in the MC patients (P=0.003). Bacteremia occurred in 25% of the FBC group and 50% in the MC group (P=0.1). In the FBC group, platelet engraftment was faster and transfusions were fewer (P<0.05). Mucositis and renal function were similar in the two groups. The MC group had higher maximum bilirubin (P=0.03) and less often normal spirometry (P=0.04) after HSCT. A 7-year-old girl in the MC group had permanent alopecia. No patients had severe acute graft-versus-host disease (GVHD). Chronic GVHD was rare. Complete donor CD3+ chimerism was more common in the MC group (P=0.01), but CD33+ engraftment was better with FBS (P=0.03). Treatment-related mortality was 4 and 15%, and 5-year survival was 89 and 85% in the FBC and MC groups. Although survival was similar, FBC is a promising alternative to MC in non-malignant disorders.

Leukemia lineage-specific chimerism analysis is a sensitive predictor of relapse in patients with acute myeloid leukemia and myelodysplastic syndrome after allogeneic stem cell transplantation.

One of the major complications after allogeneic stem cell transplantation (SCT) in patients with malignant disease is a high frequency of relapse. We have prospectively analyzed the clinical impact of recipient-derived chimeric cells in 30 patients with acute myeloid leukemia and myelodysplastic syndrome after SCT. In order to improve sensitivity and specificity, all samples were cell-separated by using immunomagnetic beads according to the patient's leukemia phenotype, expressed at diagnosis or relapse before SCT. Twelve out of 30 patients experienced a clinical relapse after SCT. Median follow-up time for patients alive and without relapse (n = 15) was 30 (16-47) months. Mixed chimerism in peripheral blood (PB) and bone marrow (BM) > or =1 month post SCT, in the leukemia-affected cell lineage, was detected in 14/30 patients. Ten of these 14 patients relapsed as compared to 2/16 with donor chimerism (DC) (P <0.01). All eight patients with MC in peripheral blood > or =1 month after SCT relapsed vs 4/22 DC patients (P < 0.001). MC was detected a median of 66 (23-332) days before hematological relapse. No correlation was found between T cell MC and relapse. In this study, chimerism analysis showed a higher sensitivity and specificity vs morphological examination. In conclusion, this study may provide a rational basis for treatment with adoptive immunotherapy at an earlier time after SCT than at present, in patients with AML and MDS, in order to treat recurrences of malignant disease.

Minimal residual disease is common after allogeneic stem cell transplantation in patients with B cell chronic lymphocytic leukemia and may be controlled by graft-versus-host disease.

Following allogeneic stem cell transplantation (SCT), we studied the presence of donor and recipient derived cells within the CD19+ B cell fraction, in patients with B cell chronic lymphocytic leukemia (CLL). The chimeric status of the six patients studied was further investigated with minimal residual disease (MRD) detection, by sequencing and using patient-specific primers derived from junctional regions of clonally rearranged immunoglobulin heavy-chain (IgH) receptor genes. To date, five of six patients are alive with a median follow-up time of 24 months (range 15-60) post-SCT. All patients experienced acute and chronic graft-versus-host disease and responded clinically to SCT. All patients were MRD positive after SCT, which correlated to mixed chimerism within the CD19+ cell fraction in all samples except one (25/26). High levels of tumor necrosis factor-alpha (TNF-alpha) and soluble interleukin-2 receptor (sIL-2R) indicated advanced disease, and patients with increased levels pre- and post-SCT were also those with the most long-lasting PCR-detectable MRD post-SCT. Hence, a high tumor burden pre-SCT may reflect the long duration of detectable MRD in patients with B-CLL after SCT. A durable anti-leukemic effect was probably important in these patients.

T cell mixed chimerism is significantly correlated to a decreased risk of acute graft-versus-host disease after allogeneic stem cell transplantation.

BACKGROUND: It has been debated whether mixed chimerism (MC) is correlated to a decreased incidence of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (SCT). METHODS: Between September 1996 and April 1999 we analyzed 102 patients for MC in the T-cell fraction post allogeneic SCT, using PCR amplification of variable numbers of tandem repeat (VNTR) loci. All samples, taken regularly post SCT, were cell separated using anti-CD3 immunomagnetic beads. RESULTS: T-cell mixed chimerism was detected in 58 out of 102 patients (57%). Patient characteristics were comparable in the T-cell MC- and donor chimeric-group (DC). The median follow-up time for the MC group was 714 days (range 58 - 1248) as compared to 427 days (range 45 - 1042) for the DC group. Overall probability of acute GVHD grades II-IV was significantly higher in the DC group as compared to the MC group (52% vs. 5%, P<0.001). In multivariate analysis T-cell DC proved to be the most significant risk factor for acute GVHD grades II-IV. The cumulative incidence of relapse, among patients with malignant disease, did not show any statistical difference between the T-cell MC patients and the DC-group. There was a tendency for better overall survival in the T-cell MC group compared to the DC group (2 yrs; 73% vs. 54%, P=0.06). Among DC patients, 14/20 (70%) deaths were due to GVHD versus none in the MC-group(P<0.001). CONCLUSION: T-cell mixed chimerism was significantly correlated to a decreased risk of moderate to severe acute GVHD and death by GVHD.

Transplantation of autologous and allogeneic bone marrow with liver from a cadaveric donor for primary liver cancer.

BACKGROUND: In histocompatibility mismatched experimental animals, a combination of T-cell-depleted autologous and allogeneic marrow may induce mixed chimerism and tolerance. Patients with large primary liver tumors have a poor outcome. We investigated whether it were possible to induce mixed chimerism and obtain an antitumor effect in a patient with a large primary liver cancer after combined liver and bone marrow transplantation (BMT). METHODS: A 46-year-old female with a primary non resectable liver cancer received a liver transplant from a cadaveric donor. Subsequently, she was conditioned with 4x2 Gy of total lymphoid irradiation, 120 mg/kg cyclophosphamide, and 7.5 Gy total body irradiation. Twelve days after liver transplantation, she received T-cell-depleted autologous:cadaveric 5/6 antigen HLA-mismatched marrow in a proportion of CD34+ cells of 0.5:3.0x10(6)/kg. Chimerism status was determined with polymerase chain reaction amplification of variable number tandem repeats from DNA obtained from CD3+, CD19+, and CD45+ magnetic-bead-separated cells. RESULTS: The early posttransplant period was uneventful; liver function was normal and the hematopoietic engraftment of donor and recipient origin was prompt. Alpha-fetoprotein levels dropped from 440 to 35 microg/l. One month after marrow transplantation, donor T-cells decreased markedly. Monoclonal antibody OKT-3 and 10(5)/kg donor T-cells were given. One month later, the patient developed diarrhea and abdominal pain. A colonoscopy showed moderate gastrointestinal acute graft-versus-host disease and a Cryptosporidium infection. Three months after BMT, she became a complete donor chimera. Chimera cells showed little, if any, reactivity in mixed lymphocyte cultures to recipient and donor cells, but reacted to third party. Five months after BMT, she developed progressive Aspergillus fumigatus pneumonia and died. No tumor was found at the autopsy. CONCLUSION: We obtained mixed donor-recipient hematopoietic chimerism without severe acute graft-versus-host-disease, after combined T-cell depleted autologous and allogeneic BMT and a transplantation of a liver from an HLA-mismatched cadaveric donor. Additional donor T-cells enhanced donor bone marrow engraftment, but rejected the autograft. On the basis of this first attempt, further clinical studies are warranted.

Poor correlation of kinetics between BCR-ABL and WT1 transcript levels after allogeneic stem cell transplantation.

After allogeneic stem cell transplantation (SCT), we evaluated the use of the Wilms' tumor gene (WT1) as a minimal residual disease (MRD) marker in 32 patients (28 chronic myeloid leukemia, three acute lymphoblastic leukemia and one acute myeloid leukemia). All patients expressed BCR-ABL and the kinetics of WT1 were compared with those of BCR-ABL using real-time quantitative PCR. WT1 expression was seen in the peripheral blood (PB) of healthy controls with a median expression level of 7 x 10(-5) (WT1/ABL ratio). The corresponding values for BCR-ABL-negative and BCR-ABL-positive patient samples were 1 x 10(-4) and 1.6 x 10(-4), respectively. Kinetic studies in individual patients showed that WT1 and BCR-ABL levels usually did not copy each other. In four out of six patients who relapsed, an increase in WT1 from the background level (10(-4)) was observed only at the time of or after relapse, and in two patients increasing WT1 levels were observed before the relapse. In addition, the WT1 values found at the time of relapse were only two logs higher than the background level, indicating a sensitivity of 10(-2). In conclusion, there is a constitutive low expression of WT1 in normal hematopoietic cells. The sensitivity and ability of WT1 to predict a relapse were poor in this study.

Fractionated TBI correlates with less T cell mixed chimerism but increased risk of relapse compared to busulphan in patients with haematological malignancies after allogeneic stem cell transplantation.

We prospectively evaluated mixed chimerism (MC) in the T cell and myeloid lineages and its correlation to busulphan, single-dose total body irradiation (TBI) and fractionated TBI (fTBI) conditioning in 180 patients with haematological malignancies after allogeneic stem cell transplantation (SCT). In all patients receiving busulphan, the area under curve (AUC) was calculated. The incidence of MC in the T cell lineage was significantly lower in patients receiving fTBI (22%) compared to those given TBI (53%, P=0.02) or busulphan (47%, P<0.01). The incidence of myeloid MC did not differ between the three groups. The overall probability of acute graft-versus-host disease grades II-IV was significantly higher in patients with complete T cell donor chimerism (49%) compared to patients with T cell MC (23%, P<0.001). The incidence of T cell and myeloid MC after SCT did not differ between low (55%), medium (42%) and high (43%) AUC levels of busulphan during conditioning. Patients receiving fTBI had a significantly higher probability of relapse compared to busulphan-treated patients (44 vs l6%, P=0.01). In multivariate analysis adjusted for diagnosis, busulphan-treated patients showed both a better survival (P=0.04) and less probability of relapse (0.03) compared to TBI-treated patients.

Increased levels of immune transcript in patients with acute GVHD after allogeneic stem cell transplantation.

After allogeneic stem cell transplantation (SCT), donor T-cells are primarily responsible for the antihost activity, resulting in graft-versus-host disease (GVHD). Three effector pathways have been described for T-cell cytotoxicity: perforin/granzyme B; Fas/Fas ligand (FasL) and secreted molecules such as TNF-alpha. The goal of this pilot study was to utilize competitive reverse transcription (RT)-PCR to evaluate the pattern of granzyme B, perforin, FasL and TNF-alpha gene expression in peripheral blood in patients after SCT. Protein levels of granzyme B, soluble FasL (sFasL) and TNF-alpha in plasma were also analyzed. Eight patients who underwent allogeneic SCT were included; five were diagnosed with acute GVHD. In the patients diagnosed with acute GVHD, we found increased levels of granzyme B, perforin and FasL mRNA, although this did not correlate with the clinical severity. However, patients with increasing levels of gene expression during acute GVHD treatment may have an increased risk of developing severe acute GVHD, as two out of three patients with increasing immune transcript levels during GVHD therapy developed life-threatening acute GVHD. In conclusion, the quantitative RT-PCR of granzyme B, perforin and FasL may serve as a guide to the clinician in diagnosing acute GVHD and monitoring treatment.

Mixed chimerism in the B cell lineage is a rapid and sensitive indicator of minimal residual disease in bone marrow transplant recipients with pre-B cell acute lymphoblastic leukemia.

One of the major problems after allogeneic bone marrow transplantation (BMT) is a high frequency of leukemia relapse. We have prospectively studied the presence of donor- and recipient-derived chimeric cells in bone marrow recipients with pre-B cell acute lymphoblastic leukemia (pre-B-ALL). The chimeric status of BMT recipients was compared to minimal residual disease (MRD) detection by analysis of immunoglobulin heavy chain (IgH) and T cell receptor (TcR) genes. Post-transplant blood and bone marrow samples from 12 patients with pre-B-ALL were studied. Five patients showed mixed chimerism (MC) in the CD19-positive cell fraction. Four of them have relapsed to date. The remaining patient with MC in the B cell lineage was also MRD positive in the same samples. All seven patients with donor chimerism in the B cell fraction remain in clinical remission (P = 0.01). In samples from all five patients having MC in the B cell lineage, the patient-specific IgH or TcR rearrangement was also detected. In three of four patients who relapsed, MC in the B cell lineage was seen more than 2.5 months prior to morphologically verified relapse. The results of this comparison suggest that routinely performed MC analysis of the affected cell lineage may facilitate post-BMT monitoring and rapid therapeutic decisions in transplanted patients with pre-B-ALL.

A graft-versus-colonic cancer effect of allogeneic stem cell transplantation.

Allogeneic stem cell transplantation (ASCT) has proved to have an important immune-mediated anti-tumour effect in patients with haematologic malignancies. There is also evidence of such an effect in patients with malignant tumours. We studied this effect of ASCT in a patient with colorectal cancer. A 77-year-old man having a primarily resected colonic cancer with disseminated lymph node involvement received ASCT from his HLA-identical sibling as the only treatment. Mixed haematopoietic chimerism was monitored using PCR-amplification of variable number tandem repeats and tumour size, assessed by repeated CT scans. Recipient leucocytes were gradually replaced by donor cells for 1 month. Continuous resolution of lymph node metastases was seen together with clinical graft-versus-host disease (GVHD). The patient died of pneumonia and cardiac insufficiency 4 months after transplantation. At autopsy, most of the metastases were necrotic, with few remaining tumour cells. Clinical and histopathological postmortem results showed a graft-versus-colorectal cancer effect.

Low-intensity conditioning and hematopoietic stem cell transplantation in patients with renal and colon carcinoma.

We have evaluated whether allogeneic hematopoietic stem cell transplantation (HSCT) could induce an antitumor effect in patients with metastatic solid tumors. A total of 12 HLA-identical siblings and 6 HLA-A-, -B- and -DR beta 1-compatible unrelated grafts were used. Diagnoses were adenocarcinoma of kidney (n=10), colon (n=6), breast (n=1) and cholangiocarcinoma (n=1). Conditioning was fludarabine 30 mg/m(2)/day for 3 days and 2 Gy of total body irradiation. Recipients of unrelated HSCT were also given thymoglobuline and two additional days of fludarabine. The median CD34+ cell dose was 7.5 x 10(6)/kg. Immunosuppression was mycophenolate mofetil and cyclosporin. Among all, 12 patients became complete donor chimeras within a median of 28, 29 and 65 days for B, myeloid and T cells, respectively. Two patients rejected the grafts, one developed marrow aplasia and three were mixed chimeras. The probability of grades II-IV acute graft-versus-host-disease (GVHD) was 57%. Regression of all tumor metastases was seen in one patient with colon carcinoma. Another patient with colon and two with renal carcinoma had regression of lung metastases, but progression of metastases in the liver and/or bone. Necrosis of lung metastasis was found in one further patient with renal carcinoma who died of graft-versus-host-disease (GVHD). In all, 10 patients died; four of transplant-related complications, one of trauma and five of progressive disease. Thus, progression was common after allogeneic HSCT in unselected patients with advanced solid tumors. However, the regression of some metastases associated with GVHD provides suggestive evidence that the GVHD effect may occur in renal and colon adenocarcinoma using reduced intensity conditioning.

Alpha/beta T-cell depleted grafts as an immunological booster to treat graft failure after hematopoietic stem cell transplantation with HLA-matched related and unrelated donors.

Allogeneic hematopoietic stem cell transplantation is associated with several complications and risk factors, for example, graft versus host disease (GVHD), viral infections, relapse, and graft rejection. While high levels of CD3+ cells in grafts can contribute to GVHD, they also promote the graft versus leukemia (GVL) effect. Infusions of extra lymphocytes from the original stem cell donor can be used as a treatment after transplantation for relapse or poor immune reconstitution but also they increase the risk for GVHD. In peripheral blood, 95% of T-cells express the αß T-cell receptor and the remaining T-cells express the γδ T-cell receptor. As αß T-cells are the primary mediators of GVHD, depleting them from the graft should reduce this risk. In this pilot study, five patients transplanted with HLA-matched related and unrelated donors were treated with αß T-cell depleted stem cell boosts. The majority of γδ T-cells in the grafts expressed Vδ2 and/or Vγ9. Most patients receiving αß-depleted stem cell boosts increased their levels of white blood cells, platelets, and/or granulocytes 30 days after infusion. No signs of GVHD or other side effects were detected. A larger pool of patients with longer follow-up time is needed to confirm the data in this study.

Allogeneic hematopoietic SCT in patients with non-malignant diseases, and importance of chimerism.

In this retrospective study, we evaluated the chimerism status and outcome in 58 patients (64 transplants) with non-malignant diseases. Reduced intensity conditioning (RIC) was given in half of the transplants. Mixed chimerism (MC) was defined as >1% recipient cells. Two consecutive samples showing >30% recipient cells were defined as high chimerism (high MC). Patients with high MC and the management of these patients were analyzed in greater detail. The overall survival rate was 87%. In total, 23 transplants were donor chimerism (DC) and 41 transplants showed some degree of MC. The incidence of MC was 78 and 50% after RIC and myeloablative conditioning, respectively (P=0.04). Acute GVHD of grades II-III was more common in patients with DC (39%) than in patients with MC (8%) (P=0.002). Owing to high MC, donor lymphocyte infusions were given in 17 cases. The level of MC was reduced in seven cases, unchanged in four cases, increased in one case and there was graft rejection in five cases. A second transplant was carried out in six cases with rejections, five are alive and in remission. We conclude that patients with non-malignant diseases, who develop MC after transplant have less acute GVHD. Despite the high incidence of MC, overall survival is promising.