Risk factors for acute graft-versus-host disease in histocompatible donor bone marrow transplantation

We have analyzed factors associated with acute graft-versus-host disease following allogeneic bone marrow transplantation in 469 patients with histocompatible sibling donors between 1979 and 1987. Overall, 46 +/- 5% (95% confidence interval) developed clinical grade II-IV acute GVHD following transplantation. In univariate analysis, patient or donor age greater than or equal to 18 years was significantly associated with increased GVHD risks (greater than or equal to 18, 63 +/- 6% grade II-IV GVHD vs. less than 18, 27 +/- 6%, P less than .0001), without incremental risk in older adults. Univariate analysis showed that donor:recipient sex match and female:female transplants were associated with less-frequent GVHD. More frequent GVHD was associated with chronic myelogenous leukemia, cytomegalovirus seropositivity, and prior donor alloimmunity (pregnancy or transfusion). Additionally, the allele HLA-A26 was associated with increased risk of GVHD (72%, P = .005) while HLA-DR3 was associated with less GVHD (31%, P = .03). Stepwise multivariate analysis confirmed the increased GVHD risks associated with older recipient age, HLA-A26 and donor:recipient gender (not female:female) and the protective effect of HLA-DR3. Similar results were found using the different analytic technique of recursive partition analysis, which identified within the adult population the lowest GVHD risk in female recipients with nonalloimmunized female donors (20%), while other gender combinations had 68% acute GVHD, regardless of donor alloimmunity. In children (less than 18 years), lower GVHD risk accompanied donor:recipient sex-matched (18%) versus mismatched (33%) BMT. Clinical trials undertaken to lessen the hazards of GVHD must be designed with appropriate attention to these reproducibly identified clinical variables associated with different GVHD risks.     

Graft-versus-host disease prevention in allogeneic bone marrow transplantation from histocompatible siblings. A pilot study using immunotoxins for T cell depletion of donor bone marrow

Seventeen patients, ages 7-53 years were transplanted with histocompatible bone marrow that had been depleted of T lymphocytes by ex vivo immunotoxin (IT) treatment. Twelve patients had high-risk acute leukemias, and five had chronic myelogenous leukemia. No other graft-vs.-host disease (GVHD) prophylaxis was used. A mixture of three anti-T-cell monoclonal antibodies conjugated to ricin were used in this study: TA-1, UCHT-1 (anti-CD3), and T101 (anti-CD5). The mean number of bone marrow cells infused was 1.5 X 10(8) mononuclear cells/kg recipient weight. Thirteen of the 17 patients demonstrated complete and sustained engraftment. Four patients experienced autologous marrow recovery and/or graft rejection. Compared with an historical group of leukemic patients who received GVHD prophylaxis with methotrexate alone or combinations of methotrexate, and prednisone plus antithymocyte globulin, (ATG) or OKT3, the IT patients with stable engraftment demonstrated shorter time to recovery of leukocytes greater than or equal to 1000mm3 for three consecutive days (median, 20 days vs. 26 days, P = .03). The recovery of total lymphocytes, B and T cell subsets, and T cell function by day 28 was highly variable, but similar, for patients in both the IT-treated group and historical controls. Four patients (ages 13, 18, 21, and 38) developed grade II skin GVHD, but none had severe GVHD. Eight of the 13 patients with durable engraftment have had posttransplant leukemic relapse. Currently only four patients remain alive; two have not relapsed posttransplant, while the other two achieved remission following posttransplant relapse. We conclude that severe GVHD was not observed in this small series with ex vivo T cell depletion for GVHD prophylaxis, and that favorable recovery of hematologic and lymphocytic function was demonstrated for cases where primary engraftment was sustained. A larger randomized controlled study will be needed to establish whether T cell depletion of donor bone marrow with IT can significantly reduce GVHD, and/or improve disease-free survival.     

Specific ex-vivo depletion of human bone marrow T lymphocytes by an anti-pan-T cell (CD5) ricin A-chain immunotoxin

We studied optimal conditions for ex vivo elimination of mature T cells from human bone marrow by T101 immunotoxin (T101-IT) with criteria applicable to graft-versus-host disease (GVHD) prophylaxis prior to allogeneic marrow transplantation. T101-IT consisted of T101 anti-CD5 monoclonal antibody conjugated to purified ricin A-chain toxin. Marrow mononuclear cells isolated by Ficoll-Hypaque or by fractionation with soybean lectin (SBA- cells) were incubated with T101-IT at 37 degrees C with or without ammonium chloride and/or verapamil as potential enhancers of immunotoxin potency. As controls, competitive inhibition studies with unconjugated T101 or irrelevant IgG2a antibody were carried out. Residual T cells were quantified by limiting dilution in phytohemagglutinin (PHA)-interleukin 2 (IL-2) feeder-cell-containing microcultures and hematopoietic progenitors by CFU-GM assay. We demonstrated that T101-IT in the range of 1-100 nM does not affect early total cell viability; that its delayed cytotoxicity is T-cell-specific, greatly enhanced by ammonium chloride, and moderately by verapamil--which also is not synergistic with ammonium chloride; and that 10 nM X 3 fractionated doses (i.e., added at 0, 1.5, and 3 hr of incubation) in the presence of 10 mM ammonium chloride for 4 hr at pH 7.8 consistently induces 2 log T cell depletion. In addition, if the same T101-IT treatment is preceded by fractionation with soybean lectin (i.e., T101-IT treatment of SBA- marrow cells), 3 log T cell depletion is accomplished. We conclude that T101-IT is highly effective in eliminating T cells from donor grafts. However, data presented here indicate that T101-IT should be associated with additional methods, such as soybean lectin fractionation, to ensure more effective ex vivo T cell depletion and acute GVHD prevention.     

T cell depletion with CAMPATH-1 in allogeneic bone marrow transplantation

A total of 282 patients with leukemia have been treated by transplantation from HLA-matched siblings using marrow depleted of T cells with CAMPATH-1 and autologous complement. The incidence of graft-versus-host disease (GVHD) of grades 2-4 was only 12% but the maximum incidence of graft failure was 15%. A significant increase in relapse cannot yet be detected in acute leukemia but relapse in chronic granulocytic leukemia (CGL) was substantially above that reported before T cell depletion. The most important predictive factor for relapse in CGL appeared to be slow engraftment. This finding suggests an alternative explanation for the graft-versus-leukemia effect other than a direct attack on leukemia cells. This is that donor T cells may affect the balance of competition between donor and recipient haemopoesis by preventing a rejection reaction to donor stem cells. Recipient leukemic cells would benefit (i.e. relapse) if recipient hemopoiesis gained an advantage. If this explanation were true we would expect extra immunosuppressive preconditioning of recipients to reduce the incidence of relapse, as well as preventing graft rejection.     

Ex vivo depletion of T cells from bone marrow grafts with CAMPATH-1 in acute leukemia: graft-versus-host disease and graft-versus-leukemia effect

BACKGROUND: Preventing graft-versus-host disease (GVHD) by depletion of T lymphocytes from the stem cell graft for transplantation remains controversial, mainly because of the perceived increase in disease recurrence. METHODS: We retrospectively analyzed the outcome of 50 consecutive individuals in remission of acute lymphoblastic leukemia (n=13; 8 in complete remission [CR]1) or acute myeloblastic leukemia (n=37; 33 in CR1), who had received marrow grafts from HLA-identical siblings. The conditioning regimen included six 2-Gy fractions of total body irradiation, succeeded by cyclophosphamide at 120 mg/kg (with mesna) followed by four fractions of 1.5 Gy to lymphoid areas. Bone marrow (n=38) or peripheral blood mobilized donor mononuclear cells (n=12) were exposed ex vivo to CAMPATH-1 (IgM and complement, or IgG; antiCD52) antibodies, without any further posttransplantation immunosuppression. RESULTS: Median patient age was 31 (range 14-51) years; 12 patients were 40 or older. Thirty-two patients were male. One patient died of pulmonary hemorrhage on day 10; another died on day 29 of interstitial pneumonitis. Except for one early death, all patients engrafted. Ten (21%) of the remaining 48 who were at risk, developed GVHD. In none was it greater than grade II. Eight patients developed serious viral infections. Four died of cytomegalovirus pneumonia, adenovirus hepatitis, and human immunodeficiency. Overall, 11 patients (22%) relapsed (4 of 33 acute myeloblastic leukemia in CR1) at a median of 235 (range 46-528) days. Mean posttransplantation follow-up was 1062 (median 560; range 10-4177) days. Thirty-three patients (66%) remained disease free at a mean of 1,118 (median 1439; range 159-4,177) days. For all patients, the performance status was between 82% and 100% (median 100). CONCLUSION: T-cell depletion with CAMPATH-1 effectively prevents GVHD, particularly the severe acute forms, without leading to excessive risk of relapse in acute leukemia.     

CD69+ resident memory T cells are associated with graft-versus-host disease in intestinal transplantation

Graft-versus-host disease (GvHD) is a common, morbid complication after intestinal transplantation (ITx) with poorly understood pathophysiology. Resident memory T cells (T_RM) are a recently described CD69+ memory T cell subset localizing to peripheral tissue. We observed that T effector memory cells (T_EM) in the blood increase during GvHD and hypothesized that they derive from donor graft CD69+T_RM migrating into host blood and tissue. To probe this hypothesis, graft and blood lymphocytes from 10 ITx patients with overt GvHD and 34 without were longitudinally analyzed using flow cytometry. As hypothesized, CD4+ and CD8+CD69+T_RM were significantly increased in blood and grafts of GvHD patients, alongside higher cytokine and activation marker expression. The majority of CD69+T_RM were donor derived as determined by multiplex immunostaining. Notably, CD8/PD-1 was significantly elevated in blood prior to transplantation in patients who later had GvHD, and percentages of HLA-DR, CD57, PD-1, and naïve T cells differed significantly between GvHD patients who died vs. those who survived. Overall, we demonstrate that (1) there were significant increases in T_EM at the time of GvHD, possibly of donor derivation; (2) donor T_RM in the graft are a possible source; and (3) potential biomarkers for the development and prognosis of GvHD exist.     

Bone marrow transplantation in miniature swine. III. Graft-versus-host disease and the effect of T cell depletion of marrow

Graft-versus-host disease (GVHD) has been evaluated in partially inbred miniature swine in order to study this complication of allogeneic bone marrow transplantation (BMT) in a major histocompatibility complex (MHC) genetically defined large animal model. Bone marrow from MHC homozygous ("parental") swine was injected into irradiated (900 rads total-body irradiation) MHC heterozygous ("F1") swine that shared one haplotype with the donor. All 18 animals successfully engrafted with donor bone marrow, and 17 of these developed skin rash of varying intensity depending on the extent of T cell depletion of infused marrow. Of 18 animals, 8 received undepleted bone marrow from exsanguinated donors and 2 also received additional peripheral blood lymphocytes (PBL) as a source of mature T cells. All 8 showed a moderate-to-severe rash, and the 2 pigs that received additional donor PBL developed the most severe rash. The cutaneous eruption seen in this model clinically, histologically, and immunologically resembled human GVHD. Two protocols of T cell depletion of donor bone marrow by antiporcine T cell monoclonal antibodies plus complement were tested for their effect on development of GVHD. The combination of two monoclonal antibodies, 74-12-4 (PT4) and 76-2-11 (PT8), had a marginal effect on the subsequent development of cutaneous manifestations of GVHD. However, treatment of the donor marrow by a combination of three monoclonal antibodies--PT4, PT8, and MSA4 (PT11)--effectively decreased the severity of the GVHD skin rash. These results indicate that (1) the GVHD associated with allogeneic bone marrow transplantation in swine is dependent on T cells in the marrow; (2) effective T cell depletion of donor marrow by monoclonal antibodies and complement does not prevent engraftment; and (3) this swine GVHD model, which allows study with F1 and homozygous parental combinations in an MHC genetically defined large animal, is particularly useful for the understanding of GVHD pathogenesis, prevention, and treatment.     

异基因造血干细胞移植受者外周血中可溶性HLA-G与急性GVHD的相关性

目的 探讨异基因造血干细胞移植(allo-HSCT)受者外周血中可溶性HLA-G(sHLA-G)的水平与急性移植物抗宿主病(aGVHD)间的相关性以及与CD4+CD25~(hlgh)调节性T淋巴细胞(Treg)水平的相关性.方法 选择27例allo-HSCT受者,将其中13例术后发生aGVHD者作为aGVHD组,14例未发生aGVHD者作为对照组.在移植预处理前、移植后第2、4、8、14周时,分别抽取两组受者清晨空腹肘静脉血2～4 ml,采用酶联免疫吸附试验双抗夹心法定量检测sHLA-G,采用流式细胞术检测CD4+CD25+Treg.动态监测术后第2和14周受者sHLA-G水平的变化;动态监测和分析术后第8和14周两组受者间sHLA-G的差异.观察sHLA-G与发生aGVHD的相关性;检测术后第14周两组受者CD4+CD25+Treg的数量,观察sHLA-G水平与CD4+CD25+Treg的相关性.结果 预处理前,对照组和aGVHD组受者sHLA-G的水平分别为(75.4±13.1)/μg/L和(47.0±14.1)btg/L,两组间差异有统计学意义(P<0.05).术后第8周和第14周,对照组受者sHLA-G的水平明显高于相应时间点aGVHD组受者,两组间差异均有统计学意义(P<0.01).对照组受者术后第14周的sHLA-G水平与第2周相比,增长了1.2～3.4倍,两时间点的差异有统计学意义(P<0.05).术后第14周,通过Spearman等级相关检验显示受者sHLA_G水平与CD4+CD25+Treg比例具有统计学上的相关性(相关系数r=0.810,P<0.05),结论 allo-HSCT后受者体内sHIA-G对aGVHD的发生起负性调节作用;sHLA-G的水平与外周血CD4+CD25~(hlgh) T淋巴细胞的比例旱正相关,二者之间可能存在相互诱导和调节的信号途径,在诱导和维持移植免疫耐受中起着重要的协同作用.     

Pemphigoid-like ocular lesions in patients with graft-versus-host disease following allogeneic bone marrow transplantation

We present two patients who developed keratitis sicca and pemphigoid-like symptoms following allogeneic bone marrow transplantation (BMT). The diagnosis of ocular graft-versus-host disease (GvHD) was considerably delayed in both. They were admitted to the reference ophthalmology and posttransplant care departments years after allogeneic BMT, when skin biopsy revealed changes typical for chronic GvHD. In both cases either systemic or local immunosuppressive treatment led to improvement of the clinical condition but did not significantly change patients' quality of life.     

The influence of T cell depletion on recovery of T cell proliferation to herpesviruses and Candida after allogeneic bone marrow transplantation

To test the influence of T cell depletion of the marrow in allogeneic bone marrow transplantation on functional T cell recovery, in vitro lymphocyte proliferation tests (LPTs) to microbial antigens were regularly performed in 23 recipients of normal BM and in 25 patients receiving BM with a fixed low number of T cells (1 x 10(5) T cells/kg body weight; recipients of T-depleted BM). The long-term recovery of positive LPT to at least 1 of the 4 tested microbial antigens--Candida, herpes simplex virus (HSV), varicella-zoster virus (VZV), and cytomegalovirus--was nearly similar in both groups: 16/23 versus 18/25. Recovery of LPT to Candida and HSV in the first 3 months appeared to be greatly influenced by prophylactic measures; only 2/23 recipients of normal BM, receiving amphotericin B, showed a positive LPT to Candida versus 13/25 recipients of T-depleted BM (P less than 0.01). In contrast, only 1/23 seropositive recipients of T-depleted BM, receiving acyclovir, showed a positive LPT to HSV versus 9/22 recipients of normal BM (P less than 0.05). A positive LPT to CMV in the first 3 months was found in 9/9 seropositive recipients of normal BM, versus in 5/11 seropositive recipients of T-depleted BM (P less than 0.05). Five of the 6 patients with a negative LPT died of CMV-interstitial pneumonia versus 1/14 with positive LPT (P less than 0.01). We conclude that in CMV-seropositive recipients of allogeneic BM, T cell depletion of the graft affects the early recovery of T cell proliferation to CMV, which is associated with a higher risk of fatal CMV-interstitial pneumonia.     

Ganciclovir-sensitive acute graft-versus-host disease in mice receiving herpes simplex virus-thymidine kinase-expressing donor T cells in a bone marrow transplantation setting

BACKGROUND: The use of donor T cells expressing the herpes simplex thymidine kinase (HSV-TK) gene followed by ganciclovir (GCV) treatment could allow for specific modulation of the alloreactivity occurring after bone marrow transplantation. We are presently exploring such an approach in a phase I clinical trial. METHODS: To examine the beneficial effect of administrating HSV-TK-expressing donor T lymphocytes +/- GCV treatment on acute graft-versus-host disease (aGVHD) control, irradiated Balb/c or C57BL/6 mice underwent transplantation with allogeneic bone marrow cells in conjunction with CD3+ allogeneic splenocytes from transgenic mice expressing an HSV-TK transgene. GCV treatment was initiated upon the occurrence of severe aGVHD. RESULTS: GCV treatment resulted in a 40-60% long-term survival rate of GVHD-free recipients having received HSV-TK-expressing T cells, whereas only 0-6% of mice survived without GCV treatment. Lethal aGVHD occurred in all the control animals having received non-HSV-TK-expressing T cells, irrespective of GCV treatment. CONCLUSION: Our results demonstrate that the administration of donor HSV-TK-expressing T cells to hematopoietic stem cell graft recipients followed by GCV treatment at the onset of severe aGVHD significantly reduces aGVHD-induced mortality and results in GVHD-free surviving recipients.     

FK 506 reverses acute graft-versus-host disease after allogeneic bone marrow transplantation in rats.

Severe graft-versus-host disease was induced by transplantation of ACI rat bone marrow and spleen cells into irradiated Lewis rat recipients. Treatment with FK 506 or cyclosporine A (CsA) was started after clinical and histologic evidence of acute GVHD was present. A 14-day course of FK 506 at 1.0 mg/kg/day could rescue 100% of the animals suffering from GVHD. In contrast only one half of the animals treated with CsA at a high dose of 25 mg/kg/day recovered. After cessation of immunosuppressive therapy, FK 506-treated animals displayed a marked prolonged disease-free interval as compared to CsA-treated bone marrow recipients. Recurrence of the disease in these animals could be prevented when FK 506 treatment was continued after the induction period with a low maintenance dose of 0.1 mg/kg/day every other day.     

Cyclosporine in human bone marrow transplantation. Serum concentration, graft-versus-host disease, and nephrotoxicity

Serum concentrations of cyclosporine were studied in 42 patients given cyclosporine for the prevention of graft-versus-host-disease (GVHD) following allogeneic bone marrow transplantation (BMT). Serum trough levels for cyclosporine were determined in each patient at least once weekly during the first 3 months and were compared with the occurrence of GVHD and with nephrotoxicity. Cyclosporine was given as 20 mg/kg i.m. or as a 24-hr infusion for the first 5-7 days. This was followed by a single daily oral dose of 12.5 mg/kg for 6 months. Cyclosporine was then gradually reduced and stopped after one year. After a median observation period of 2 years 25 of the 42 patients (59%) are alive. Twenty six patients (62%) developed GVHD, which was stage II or more in 11 (26%) and fatal in 2 patients (5%). Five patients developed GVHD 6-8 weeks after withdrawal of cyclosporine one year after BMT. All patients improved after restarting cyclosporine. No correlation between cyclosporine serum concentration and GVHD was observed, but patients with GVHD had greater fluctuations of their serum trough levels. Serum creatinine increased in all patients soon after BMT and was correlated with cyclosporine serum concentration during the first month. Serum creatinine, however, rose further despite lower cyclosporine concentrations in the second month. These results show that cyclosporine effectively reduces the severity, but not the incidence, of GVHD suggesting that there is a subset of cells resistant to cyclosporine. The therapeutic range, however, between high doses (which are often associated with nephrotoxicity) and the minimal effective dose of cyclosporine, has yet to be defined.     

Monoclonal antibodies for the prevention of graft-versus-host disease and marrow graft rejection. The depletion of T cell subsets in vitro and in vivo

One of the major complications of allogeneic bone marrow transplantation is graft-versus-host disease. This can be avoided by removing the mature T cells from the marrow, most conveniently by the use of monoclonal antibodies. However, T cell purging results in an increased tendency for the recipient to reject the donor marrow. We have developed monoclonal antibodies to L3/T4 and Lyt-2 that specifically deplete functional T cell subsets in mice. We demonstrate that such reagents can be used to control both graft-versus-host disease and marrow rejection in mouse models of bone marrow transplantation across one-haplotype or two-haplotype major histocompatibility differences. Such strategies to abrogate host resistance, by administration of anti-T-cell monoclonal antibodies to the recipient, may complement marrow T cell purging for human allogeneic bone marrow transplantation.     

Idiopathic small airways pathology in patients with graft-versus-host disease following allogeneic bone marrow transplantation

In a retrospective analysis (July 1979 to March 1984) of 120 allogeneic adult bone marrow transplant recipients, we identified seven patients with small-airway disease for whom no microbiologic agent was detected. Six had pulmonary function studies demonstrating air flow obstruction. Five of the seven patients had an open-lung biopsy showing pathologic changes within small airways; these varied from early bronchiolar wall damage to bronchiolitis obliterans. The inflammatory cell infiltrate was peribronchiolar, and consisted of polymorphonuclear leukocytes and lymphocytes in varying proportions. Three of the seven patients recovered following increased immunosuppressive therapy; the other four died. Because all seven patients had acute and chronic graft-versus-host disease, in the absence of any identifiable pathogen, we postulate that small-airway damage represents one of the facets of graft-versus host-disease. An additional analysis of 26 patients with respiratory symptomatology and available histologic material supports the hypothesis that small-airway disease in bone marrow transplant patients represents a risk factor for the subsequent development of respiratory opportunistic infections.     

The effect of G-CSF-stimulated donor marrow on engraftment and incidence of graft-versus-host disease in allogeneic bone marrow transplantation

Graft-versus-host disease (GVHD) and infection are major obstacles to successful allogeneic bone marrow transplantation (allo-BMT). In an attempt to improve the results of HLA-identical sibling BMT, we investigated the effect of accelerating hemopoietic reconstitution and reducing acute GVHD (aGVHD) in allo-BMT receiving G-CSF-stimulated donor marrow and the preliminary biological mechanism. The donors of 30 patients (study group) with leukemia were given G-CSF 3-4 microg/kg/d for 7 doses prior to marrow harvest. The results of subsequent engraftment in the recipients were compared with those of 18 patients without G-CSF (control group). Five donors themselves were studied to assess the effects of G-CSF on the hematopoietic progenitor cells and lymphocyte subsets in the bone marrow (BM). We observed that the stimulated BM yielded higher numbers of nucleated cells as well as CFU-GM and CD34+ cells (p<0.01), and that hemopoietic reconstitution was accelerated. The median number of days of granulocyte count exceeding 0.5x10(9)/L and platelet count exceeding 20x10(9)/L was 16 (range 10-23 d) and 18.5 (range 13-31 d), respectively (control group: median 22 d, range 13-29 d and median 23 d, range 17-34 d; p=0.001). The incidence of grade II-IV severe aGVHD was very low, with only 1 case (3.3%) with acute grade II aGVHD limited to the skin in the study group. Five of 18 patients in the control group manifested grade II-IV severe aGVHD (27.8%, p=0.02). The number of T-lymphocyte subsets in the harvested BM using G-CSF stimulation was changed. In the G-CSF-stimulated marrow group, CD4+ decreased and CD8+ increased significantly (p=0.02). The changes of progenitor cells and T-lymphocyte subsets in donors' BM from pre- and post-G-CSF stimulation showed that the percentage of CD4+ reduced (p=0.04) and that of CD8+ increased (p=0.06), while that of CD34+ also increased (p=0.002). The incidence of chronic GVHD and relapse had no significant difference between both groups. These results indicate that allo-BMT in BM G-CSF priming can accelerate engraftment and minimize the incidence of severe aGVHD. There is a trend in favor of improved transplantation-related mortality.     

Increased donor CD86+CD14+ cells in the bone marrow and peripheral blood of patients with chronic graft-versus-host disease

BACKGROUND: Based on experimental models, chronic graft-versus-host disease (cGVHD) may depend on activated donor antigen-presenting cells presenting host antigens to donor T cells. METHODS: Peripheral blood (PB) and marrow samples from 24 patients with cGVHD and 17 patients without GVHD after an allogeneic hematopoietic stem-cell transplant were analyzed by flow cytometry. The absolute number of myeloid dendritic cells (mDC) (BDCA1+CD19-), plasmacytoid DC (pDC) (BDCA2+CD123+) and monocytes (CD45+CD14+), and mean fluorescence intensity of costimulatory molecules and chemokine receptors were assessed in each antigen-presenting cell population. RESULTS: Patients with cGVHD showed increased numbers of marrow monocytes when compared with patients without cGVHD (P=0.006). Moreover, monocytes of cGVHD patients had greater CD86 mean fluorescence intensity in marrow (P=0.02) and PB (P=0.04). Treatment with prednisone resulted in decreased CD86 expression in marrow (P=0.02) and PB (P=0.04) monocytes. The number and phenotype of mDC and pDC were similar in patients with or without cGVHD. Full-donor chimerism was detected in the PB of all patients, and in purified CD14+ monocytes from three cGVHD patients. CONCLUSION: Our results show an increased activation of donor-derived marrow and blood monocytes in patients with cGVHD, possibly suggesting the need to target monocytes in the treatment of cGVHD.