Clinical aspects of cytomegalovirus infection after allogenic bone marrow grafts

CMV infection is one of the major infection after bone marrow transplantation. CMV viremia was systematically studied in 66 patients with aplastic anemia or leukemia undergoing BMT. 57% patients had CMV viremia with a frequency peak between 7 and 9 weeks after transplant. Clinical symptoms found during viremia were pancytopenia, fever, cytolytic hepatitis. Interstitial pneumonitis was found only in 4 cases. In 3 cases, viremia was not associated with clinical symptoms. Survival was identical to the group of patients without viremia. Viremia was positively associated with the presence of high anti-CMV antibody titer in donor or recipient before transplant, or to a lymphocyte proliferative response against CMV antigens in donor or recipient before BMT. Granulocyte transfusions increased the frequency of CMV viremia. CMV infection was significantly associated with acute and chronic graft versus host disease. The relation showed between these parameters and viremia provides a basis for an accurate diagnosis of CMV infection and a better background for the study of prophylactic or curative treatment of CMV infection.     

Human memory B cells transferred by allogenic bone marrow transplantation contribute significantly to the antibody repertoire of the recipient

The bone marrow is an important source of Abs involved in long-term protection from recurrence of infections. Allogenic bone marrow transplantation (BMT) fails to restore this working memory. Attempts to overcome this immunodeficiency by immunization of the donor have not been very successful. More needs to be known about transfer of B cell memory by BMT. We tracked memory B cells from the donor to the recipient during BMT of a girl with leukocyte adhesion deficiency. Vaccination of her HLA-identical sibling donor 7 days before harvest induced Haemophilus influenzae type b (Hib) capsular polysaccharide (HibCP)-specific B cells readily detectable in marrow and blood. BMT did not lead to spontaneous production of HibCP Abs, but the recipient responded well to booster immunizations 9 and 11 mo after BMT. HibCP-specific B cells were obtained 7 days after the vaccinations, and their V(H) genes were sequenced and analyzed for rearrangements and unique patterns of somatic hypermutations identifying clonally related cells. Ninety (74%) of 121 sequences were derived from only 16 precursors. Twelve clones were identified in the donor, and representatives from all of them were detected in the recipient where they constituted 61 and 68% of the responding B cells after the first and second vaccinations, respectively. No evidence for re-entry of memory clones into the process of somatic hypermutation was seen in the recipient. Thus, memory B cells were transferred from the donor, persisted for at least 9 mo in the recipient, and constituted the major part of the HibCP-specific repertoire.     

Cytogenetic studies using Q-band polymorphisms in patients with AML receiving marrow from like-sex donors

Summary After bone marrow transplantation (BMT), it is important to monitor the bone marrow and lymphoid cell populations of the recipient to document engraftment. When donor and recipient are of unlike sex, the sex chromosomes serve as a useful marker to determine cellular origin. When donor and recipient are of like sex, autosomal heteromorphisms can be used to identify the origin of cells in metaphase. Using Q-banding, we found that 17 of 20 patient/donor pairs (85%) examined showed at least one chromosome heteromorphism that distinguished between recipient and donor cells with certainty. Five of the patients were followed up after BMT in order to document engraftment. Donor metaphases could be detected in the marrow within two weeks of BMT when the graft was successful. Chimaerism was detected in the lymphocyte population even when the graft persisted. In a case of graft failure, donor cells did not persist in the marrow, and the lymphocyte population did not convert to donor type. These studies demonstrate that autosomal heteromorphisms are useful in the study of myeloid and lymphoid chimaeric states after BMT.     

Alterations of glycosphingolipid-based blood group antigen expression on erythrocytes and in plasma studied on consecutive samples after a blood group O to A bone marrow transplantation.

A blood group A1Le(a-b+) individual with chronic myeloid leukaemia had received a bone marrow graft from an HLA-identical OLe(a+b-) donor. Twelve months after bone marrow transplantation (BMT), the red blood cells of the patient became agglutinable with anti-A blood group reagents. To elucidate whether the blood group A antigen expression was of plasma or of bone marrow origin, total non-acid glycosphingolipid fractions were prepared from red blood cells and plasma collected 17 months after BMT, and from plasma collected 13, 15 and 19 weeks after BMT. The glycolipid fractions were analysed by thin-layer chromatography and immunostained with monoclonal A-antibodies, and permethylated and permethylated-reduced derivatives of selected plasma samples were analysed by mass spectrometry. The results strongly indicate the presence of host bone marrow-produced blood group A red blood cells. Furthermore, the presence of a blood group H active pentaglycosylceramide type 1 (H-5-1) (Table I), characteristic for an OLe(a-b-) secretor, was seen in plasma 3-4 weeks before clinical chronic graft versus host disease (GVHD). After treatment of chronic GVHD, this expression disappeared. The blood group ALeb (A-7-1) antigen produced by the recipient seems to be present and to increase with time in all plasma samples. This also seems to be the case for the Leb and A-6-1 antigens.     

Recipient nonhematopoietic antigen-presenting cells are sufficient to induce lethal acute graft-versus-host disease

The presentation pathways by which allogeneic peptides induce graft-versus-host disease (GVHD) are unclear. We developed a bone marrow transplant (BMT) system in mice whereby presentation of a processed recipient peptide within major histocompatibility complex (MHC) class II molecules could be spatially and temporally quantified. Whereas donor antigen presenting cells (APCs) could induce lethal acute GVHD via MHC class II, recipient APCs were 100-1,000 times more potent in this regard. After myeloablative irradiation, T cell activation and memory differentiation occurred in lymphoid organs independently of alloantigen. Unexpectedly, professional hematopoietic-derived recipient APCs within lymphoid organs had only a limited capacity to induce GVHD, and dendritic cells were not required. In contrast, nonhematopoietic recipient APCs within target organs induced universal GVHD mortality and promoted marked alloreactive donor T cell expansion within the gastrointestinal tract and inflammatory cytokine generation. These data challenge current paradigms, suggesting that experimental lethal acute GVHD can be induced by nonhematopoietic recipient APCs.     

B cell development and regulation after T cell-depleted marrow transplantation

Antibody secreting B lymphocytes from immunized donors can be adoptively transferred after T cell-depleted marrow transplantation to produce protective levels of antibody in the recipient. We have investigated whether these transferred lymphocytes remain subject to continued clonal selection and subsequently became memory B cells even in the initial absence of T cells. Twenty-eight donor/recipient pairs were randomized pretransplant to be immunized or not with tetanus toxoid (TT). The recipients were then vaccinated with TT at 3, 6, and 12 mo posttransplant, and the anti-TT antibody response (IgG and IgM) was measured. Only when both donor and recipient were immunized pretransplant could the recipient respond to antigen challenge within the first year posttransplant. Examination of the spectrotype pattern of the recipient anti-TT antibody shows that selection of B cell clones continues, so that T cell depletion does not prevent the appearance of oligoclonal antibody responses. However, because the spectrotype pattern of the recipient did not match the donors, B cell regulatory mechanisms in donor and recipient are nonidentical. These data contrast with observations made in recipients of non-T cell-depleted marrow and serve to illustrate the role of T lymphocytes in the induction and regulation of secondary antibody responses in man. The results also suggest that optimal humoral responses to any antigen after T cell depletion can only occur when both donor and recipient are immunized pretransplant, a prediction borne out by studies on the influence of donor cytomegalovirus status on the severity of cytomegalovirus infection in the recipient.     

Nonmyeloablative bone marrow transplantation of BXSB lupus mice using fully matched allogeneic donor cells from green fluorescent protein transgenic mice

Male BXSB mice, a mouse model of systemic lupus erythematosus, were given bone marrow transplants (BMT) at 20 wk of age using MHC-matched donor cells and nonmyeloablative conditioning (550 cGy irradiation). Transplanted mice and irradiation controls were followed for a period of 20 wk. Mice transgenic for green fluorescent protein were used as donors to allow tracking of donor cells and a determination of chimerism. Radiation controls had reduced renal pathology at 10 wk posttransplant, but not at 20 wk compared with untreated mice, while nonmyeloablative BMT mice had significantly reduced pathology at both time intervals. The monocytosis characteristic of older BXSB mice was also reduced by BMT, but the treatment did not prevent production of Ab to dsDNA. A stable chimerism of 24-40% donor CD45-positive cells was achieved in spleen and bone marrow, and there was no evidence of clinical graft vs host disease. Donor cells were detected in most recipient organs, notably the thymus and renal glomeruli. The results suggest that complete depletion of mature lymphocytes or of progenitor stem cells is not required to control lupus nephritis in BXSB mice.     

Busulfan as a Myelosuppressive Agent for Generating Stable High-level Bone Marrow Chimerism in Mice

Bone marrow transplantation (BMT) is often used to replace the bone marrow (BM) compartment of recipient mice with BM cells expressing a distinct biomarker isolated from donor mice. This technique allows for identification of donor-derived hematopoietic cells within the recipient mice, and can be used to isolate and characterize donor cells using various biochemical techniques. BMT typically relies on myeloablative conditioning with total body irradiation to generate niche space within the BM compartment of recipient mice for donor cell engraftment. The protocol we describe here uses myelosuppressive conditioning with the chemotherapeutic agent busulfan. Unlike irradiation, which requires the use of specialized facilities, busulfan conditioning is performed using intraperitoneal injections of 20 mg/kg busulfan until a total dose of 60-100 mg/kg has been administered. Moreover, myeloablative irradiation can have toxic side effects and requires successful engraftment of donor cells for survival of recipient mice. In contrast, busulfan conditioning using these doses is generally well tolerated and mice survive without donor cell support. Donor BM cells are isolated from the femurs and tibiae of mice ubiquitously expressing green fluorescent protein (GFP), and injected into the lateral tail vein of conditioned recipient mice. BM chimerism is estimated by quantifying the number of GFP+ cells within the peripheral blood following BMT. Levels of chimerism >80% are typically observed in the peripheral blood 3-4 weeks post-transplant and remain established for at least 1 year. As with irradiation, conditioning with busulfan and BMT allows for the accumulation of donor BM-derived cells within the central nervous system (CNS), particularly in mouse models of neurodegeneration. This busulfan-mediated CNS accumulation may be more physiological than total body irradiation, as the busulfan treatment is less toxic and CNS inflammation appears to be less extensive. We hypothesize that these cells can be genetically engineered to deliver therapeutics to the CNS.     

Strategic nonmyeloablative conditioning: CD154:CD40 costimulatory blockade at primary bone marrow transplantation promotes engraftment for secondary bone marrow transplantation after engraftment failure

There is an increased risk of failure of engraftment following nonmyeloablative conditioning. Sensitization resulting from failed bone marrow transplantation (BMT) remains a major challenge for secondary BMT. Approaches to allow successful retransplantation would have significant benefits for BMT candidates living with chronic diseases. We used a mouse model to investigate the effect of preparative regimens at primary BMT on outcome for secondary BMT. We found that conditioning with TBI or recipient T cell lymphodepletion at primary BMT did not promote successful secondary BMT. In striking contrast, successful secondary BMT could be achieved in mice conditioned with anti-CD154 costimulatory molecule blockade at first BMT. Blockade of CD154 alone or combined with T cell depletion inhibits generation of the humoral immune response after primary BMT, as evidenced by abrogation of production of anti-donor Abs. The humoral barrier is dominant in sensitization resulting from failed BMT, because almost all CFSE-labeled donor cells were killed at 0.5 and 3 h in sensitized recipients in in vivo cytotoxicity assay, reflecting Ab-mediated cytotoxicity. CD154:CD40 costimulatory blockade used at primary BMT promotes allogeneic engraftment in secondary BMT after engraftment failure at first BMT. The prevention of generation of anti-donor Abs at primary BMT is critical for successful secondary BMT.     

Cell-cell cooperation in lymphocyte colony formation: studies in human allogeneic marrow transplantation

The pace of restoration of phytohemagglutinin- (PHA) stimulated lymphocyte colony-forming response was investigated in 50 bone marrow transplant (BMT) recipients (49 allogeneic, 1 syngeneic) studied on 86 occasions. On the majority of occasions (28 of 48), patients studied early (3 to 8 wk) after BMT failed to make detectable lymphocyte colonies, whereas patients studied late (greater than 6 mo) after BMT displayed responses comparable to those of healthy adult volunteers. The sequential study of 10 of the 15 patients with positive lymphocyte colony-forming responses early after BMT revealed that this response is short-lived. The results of recipient donor mixing experiments and experiments involving the addition of the lymphokine interleukin 2 (IL 2) to recipient cells indicated that lymphocytes obtained from unresponsive recipients evaluated early after BMT can be driven to colony formation, and suggest that the major limiting component in such subjects is functional T help.     

Role of immunoregulatory donor T cells in suppression of graft-versus-host disease following donor leukocyte infusion therapy

In murine models of allogeneic bone marrow transplantation (BMT), MHC-mismatched recipients given a delayed infusion of donor leukocytes (DLI) at 21 days posttransplant develop significant GVHD whereas MHC-matched recipients do not. The current study was initially designed to test the hypothesis that small numbers of T cells in the MHC-mismatched donor bone marrow (BM) graft exacerbated graft-vs-host disease (GVHD) when DLI was administered at 21 days after BMT. Ex vivo depletion of Thy1+ cells from the donor BM had no impact on the severity of GVHD after DLI. However, depletion of donor T cells in vivo with a Thy1 allele-specific mAb given after BMT resulted in significantly more severe GVHD after DLI. Similar results were obtained in a MHC-matched model of allogeneic BMT, indicating that this was a general phenomenon and not model dependent. These results indicated that a population of donor-derived Thy1+ cells suppressed graft-vs-host reactivity after DLI. Results of experiments with thymectomized recipients demonstrated that an intact thymus was required for generation of the immunoregulatory donor cells. Experiments using TCR beta-chain knockout mice as BM donors indicated that the immunosuppressive Thy1+ cells coexpressed alphabetaTCR heterodimers. Similar experiments with CD4 and CD8 knockout donor BM suggested that the immunoregulatory Thy1+alphabetaTCR+ cells consisted of two subpopulations: a CD4+CD8- subpopulation and a CD4-CD8- subpopulation. Together, these results show that thymus-derived, Thy1+alphabetaTCR+ donor cells generated early after allogeneic BMT suppress the graft-vs-host reactivity of T cells given as DLI. These cells may mediate dominant peripheral tolerance after allogeneic BMT.     

Development of a single probe for documentation of chimerism following bone marrow transplantation.

Although numerous genetic markers are available for studying chimerism after bone marrow transplantation (BMT), there remains a need for a practical and highly informative method that is applicable in the early posttransplantation period. Using DNA restriction-fragment-length polymorphisms (RFLPs), we have evaluated the feasibility of developing a single synthetic oligonucleotide probe to study post-BMT chimerism. We have thus tested three candidate probes, termed O-3315-32, O-3315-80, and O-AY-29, that are homologous to tandemly repetitive sequences. Our results demonstrated donor-specific and recipient-specific fragments in 11 of 11 HLA-matched sibling pairs tested using probes O-3315-32 and O-3315-80. When probe O-AY-29 was used, 14 of 17 sibling pairs showed both donor and recipient markers, one had only a recipient marker, and two were identical. We showed that each of the three synthetic probes was effective in documenting donor marrow engraftment, mixed hematopoietic chimerism, the patient's pre-BMT phenotype (by using cultured skin fibroblasts obtained after BMT), and the origin of the malignant hematopoietic cells (i.e., of donor or recipient origin) in patients who developed recurrent hematologic malignancy following BMT. Compared with the use of cloned genomic probes, there are several important advantages to the use of synthetic oligonucleotide probes in studying post-BMT chimerism. Synthetic probes have absolute hybridization specificity and can be designed to suit the purposes of an individual study, since they have adjustable specificity that can be altered by changes in the length of the probe and by changes in the hybridization temperature. A single synthetic probe analogous to several highly polymorphic loci can have a polymorphism information content sufficiently high so that all but a small percentage of BMT patients could be followed easily; for example, if a probe were complementary to three highly polymorphic unlinked loci, it would discriminate approximately 98% of sibling donor/recipient pairs. This would be accomplished using only one restriction-endonuclease digestion and only one gel electrophoresis. Since other genetic markers, e.g., red blood cell antigens, immunoglobulin allotypes, and chromosome analysis, are not uniformly informative and, in some cases, cannot be used in the early posttransplantation period, the use of synthetic oligonucleotide probes for analysis of DNA RFLP is emerging as the method of choice for studies of post-BMT chimerism. This method will allow for the development of new knowledge that has not been possible with previous methods.     

The Additive Effect of Mesenchymal Stem Cells and Bone Morphogenetic Protein 2 on γ-Irradiated Bone Marrow in Mice

Irradiation from γ-rays can cause severe damage to bone marrow and hematopoietic tissues. Presently, the most effective method available to treat severe hematopoietic injury is a bone marrow transplant (BMT). Allogeneic BMT is a difficult technique to perform due to the differences in human leukocyte antigen proteins between the donor and recipient, with acute graft-versus-host disease being a major complication of the technique. This limits the widespread applicability of allogeneic BMT. To develop a novel treatment for acute hematopoietic damage, we transplanted bone marrow derived mesenchymal stem cells (MSCs) into recipient mice and treated them with recombinant human bone morphogenetic protein 2 (rhBMP2) to investigate whether MSCs and rhBMP2 could additively promote the restoration of hematopoietic function. MSCs are vital components of the hematopoietic microenvironment that supports hematopoiesis, and bone morphogenic protein is a key factor in hematopoiesis. The 30-day survival rate as well as the numbers of nucleated cells, bone marrow colony-forming unit-granulocyte macrophages, spleen colony-forming units and peripheral blood cells were enumerated. The results showed that, after γ-irradiation and transplantation, MSCs and rhBMP2 additively promoted and improved hematopoietic restoration and function in vivo and in vitro. This additive effect of MSCs and rhBMP2 may one day provide a novel means of treating acute hematopoietic damage.     

Requirements for the adoptive transfer of antibody responses to a priming antigen in man

Antibody responses to recall vaccines can be adoptively transferred after marrow transplantation in man. Transfer of responses to priming Ag has not been successful, although this would broaden the range of organisms to which recipients could be protected. To investigate the importance of T cells and Ag in such transfer we primed marrow donors with keyhole limpet hemocyanin (KLH) 1 or 3 wk before marrow harvesting. B cells secreting IgM and IgG anti-KLH antibody were present in donor marrow at both 1 and 3 wk after immunization. After T cell depletion, donor marrow was infused into chemo-irradiated recipients, half of whom were immunized pretransplant with KLH. We found no evidence for the transfer of the IgM component of the response. Clonal expansion of the transferred IgG antibody-secreting cells with a corresponding rise in recipient serum IgG antibody levels was seen only when donors were primed 3 wk before marrow harvest and when the recipients were also immunized. IEF and immunoblotting demonstrated that successful transfer coincided with maturation of the IgG primary response from a polyclonal to an oligoclonal pattern and confirmed that donor oligoclonal bands appeared in the recipient serum. We conclude that the immunization protocols required for the transfer of antibody responses to priming Ag reflect the initial dependence of unprimed B cells on T cell help and on prolonged Ag stimulation. Ag-stimulated primary B cells in T cell-depleted marrow respond only to the noncognate growth and differentiation signals available in the chemo-irradiated recipient after an initial period of clonal selection and expansion in the donor which is both T cell and Ag dependent. Even after this initial selection, continued expansion of antibody-secreting clones in recipients retains an absolute dependence on Ag stimulation. Immunization techniques to protect transplant recipients against organisms such as Pseudomonas and CMV may need to be modified accordingly.     

Dissociation of hemopoietic chimerism and allograft tolerance after allogeneic bone marrow transplantation.

Creation of stable hemopoietic chimerism has been considered to be a prerequisite for allograft tolerance after bone marrow transplantation (BMT). In this study, we demonstrated that allogeneic BMT with bone marrow cells (BMC) prepared from either knockout mice deficient in both CD4 and CD8 T cells or CD3E-transgenic mice lacking both T cells and NK cells maintained a high degree of chimerism, but failed to induce tolerance to donor-specific wild-type skin grafts. Lymphocytes from mice reconstituted with T cell-deficient BMC proliferated when they were injected into irradiated donor strain mice, whereas lymphocytes from mice reconstituted with wild-type BMC were unresponsive to donor alloantigens. Donor-specific allograft tolerance was restored when donor-type T cells were adoptively transferred to recipient mice given T cell-deficient BMC. These results show that donor T cell engraftment is required for induction of allograft tolerance, but not for creation of continuous hemopoietic chimerism after allogeneic BMT, and that a high degree of chimerism is not necessarily associated with specific allograft tolerance.     

Problems posed by the preparation of specific anti-cytomegalovirus immunoglobulins

The authors describe the preparation of a first batch of intravenous cytomegalovirus (CMV) immune globulin at the Nancy Regional blood transfusion centre. Immune plasmas were selected from 3 640 healthy volunteer blood donors on the basis of CF antibody titers to CMV (Kolmer's method modified) of, at least, 1:8; plasmas from approximately 10% of the donors were therefore selected. The 68 liters of pooled immune plasma had à CF antibody titer of 1:16 (CMV antibody titers of 1: 10 000 and 1: 640 when tested in the ELISA assay and passive hemagglutination assay respectively). Intravenous immune globulin was produced from pooled plasma by Cohn fractionation and treatment with pepsin at pH 4; 4.8 liters of immune globulin were prepared and divided in 96 doses of 50 ml each. The final product was found to have a CMV antibody titer of 1: 32 (CF) 1: 50 000 (ELISA) or 1: 2 560 (passive hemagglutination). Recent reports on the preparation of CMV immune globulin are briefly reviewed.     

Absence of host tumor necrosis factor receptor 1 attenuates manifestations of idiopathic pneumonia syndrome

The interaction of TNF-alpha with TNF receptor 1 (TNFR1) activates several signal transduction pathways that lead to apoptosis or NF-kappa B-dependent inflammation and immunity. We hypothesized that host TNFR1 expression contributes to noninfectious lung injury and inflammation commonly observed after bone marrow transplantation (BMT), termed idiopathic pneumonia syndrome (IPS). C57BL/6 TNFR1-sufficient (TNFR1(+/+)) and -deficient (TNFR1(-/-)) mice were total body irradiated with or without cyclophosphamide conditioning and were given bone marrow plus IPS-inducing donor spleen T cells from B10.BR wild-type mice. TNFR1(-/-) recipient mice exhibited improved early post-BMT survival associated with decreased permeability edema. In addition, the low lung compliance measured in anesthetized, ventilated TNFR1(+/+) mice on day 7 after BMT was restored to baseline during TNFR1 deficiency. Importantly, bronchoalveolar lavage fluid (BALF) inflammatory cells from TNFR1(-/-) vs. TNFR1(+/+) mice generated less nitric oxide (.NO) and nitrating species and exhibited suppressed programmed cell death as assessed using flow cytometry. However, cellular infiltration and levels of proinflammatory cytokines and chemokines were generally higher in BALF collected on day 7 after BMT from TNFR1(-/-) compared with TNFR1(+/+) recipient mice. Our results support a major role of host TNFR1 in regulation of .NO production and lung dysfunction after allogeneic BMT.     

Time course of onset and decay of humoral natriuretic activity in the rat.

The natriuretic mechanism.tic activity shown in earlier cross-circulation experiments to develop in the blood of rats undergoing sustained vascular expansion has been further characterized. Following whole blood infusion and urine reinfusion of the donor rat, a cross-circulated isovolaemic partner exhibits a natriuresis of gradual onset, requiring 60-80 min to reach a peak (0.04-3.24 muequiv./min per gram kidney weight). The gradual feature of recipient natriuresis was unchanged by infusing the donor rat 1 h prior to cross-circulation. Once developed, the recipient natriuresis was sustained when fluid depletion by the renal response was prevented, but was reversible with a half-life of about 30 min on interruption of the cross-circulation; reconnection of cross-circulation promptly restored recipient natriuresis. No significant natriuresis (0.04-0.16 muequiv/min per gram kidney weight) occurred in the recipients if the donors in comparable cross-circulations were not infused. These findings confirm that a natriuretic activity develops in the blood as a consequence of vascular expansion, and reveal that the activity has a slowly developing and reversible action on the renal natriure     

CMV infections in bone marrow transplanted patients--evaluation of prophylaxis with Cytotect (CMV hyperimmuneglobulin)

Cytomegalovirus (CMV) infection is a frequent and clinically important infection following bone marrow transplantation. Candidates for this study were patients admitted for transplantation: 22 patients received bone marrow from a HLA-identical, MCR-nonreactive sibling, in 9 patients an autologous BMT was performed. The anti-CMV IgG (Cytotect) was administered at a dosage of 1 ml/kg on days -7, 13, 33, 53, 73 and 93 after BMT. 5 patients in the very beginning of our BMT program did not receive Cytotect. Patients were given random blood products from the bloodbank not tested for CMV positivity. Active CMV infection or seroconversion in our patients was defined as a rise in IgG titer against the late antigen of fourfold or more or an IgM increase. In the allogeneic BMT group the pretransplant serological status was in 6 cases negative in recipients and donor, in 7 patients positive in recipients and negative in donors, and in 4 patients positive in recipients and donors. Of the 6 patients seronegative in recipients and donors, 3 developed active infection and of the 7 patients pretransplant positive with seronegative donors 3 developed active infection and 4 latent infections during the period from 2 to 100 days following grafting. 1 patient out of the group transplanted in third partial remission of AML developed interstitial pneumonia and died on day +30.4 of the 4 cases with seropositivity of recipients and donors developed active CMV infection. Of 9 patients with autologous transplantation 6 patients were pretransplant seropositive. 3 of these 6 developed active infection and 2 latent infection 30 to 180 days after grafting.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immune Reconstitution Kinetics following Intentionally Induced Mixed Chimerism by Nonmyeloablative Transplantation

Establishing mixed chimerism is a promising approach for inducing donor-specific transplant tolerance. The establishment and maintenance of mixed chimerism may enable long-term engraftment of organ transplants while minimizing the use of immunosuppressants. Several protocols for inducing mixed chimerism have been reported; however, the exact mechanism underlying the development of immune tolerance remains to be elucidated. Therefore, understanding the kinetics of engraftment during early post-transplant period may provide insight into establishing long-term mixed chimerism and permanent transplant tolerance. In this study, we intentionally induced allogeneic mixed chimerism using a nonmyeloablative regimen by host natural killer (NK) cell depletion and T cell-depleted bone marrow (BM) grafts in a major histocompatibility complex (MHC)-mismatched murine model and analyzed the kinetics of donor (C57BL/6) and recipient (BALB/c) engraftment in the weeks following transplantation. Donor BM cells were well engrafted and stabilized without graft-versus-host disease (GVHD) as early as one week post-bone marrow transplantation (BMT). Donor-derived thymic T cells were reconstituted four weeks after BMT; however, the emergence of newly developed T cells was more obvious at the periphery as early as two weeks after BMT. Also, the emergence and changes in ratio of recipient- and donor-derived NKT cells and antigen presenting cells (APCs) including dendritic cells (DCs) and B cells were noted after BMT. Here, we report a longitudinal analysis of the development of donor- and recipient-originated hematopoietic cells in various lymphatic tissues of intentionally induced mixed chimerism mouse model during early post-transplant period. Through the understanding of immune reconstitution at early time points after nonmyeloablative BMT, we suggest guidelines on intentionally inducing durable mixed chimerism.