Prevention of graft failure by an anti-HLFA-1 monoclonal antibody in HLA-mismatched bone-marrow transplantation

Assessing the Efficacy of Alkylating Agent Regimens in the Treatment of Infantile Malignant Osteopetrosis: Cyclophosphamide, Busulfan, or Thiotepa

Infantile malignant osteopetrosis is a debilitating disease that requires total bone marrow irradiation and transplant procedures for patients to survive. The major complication of this procedure is graft vs host disease (GVHD), followed by infections and end organ toxicity. Therefore, current research efforts into treatment mainly aim to reduce GVHD while limiting infections and organ toxicity. Different regimens of alkylating agents have been used to try to reduce GVHD. The most common regimen is cyclophosphamide (Cy) with busulfan (Bu), followed by Cy with Bu and thiotepa (Thio). This meta-analysis aimed to evaluate the efficacy of different treatments by comparing mortality and morbidity causes and rates across groups. The mean one-year survival rate for the Cy, Bu, Thio regimen studies in the human leukocyte antigen (HLA) unmatched group (45.01%) was statistically lower than the one-year survival rate for the studies using just a Cy, Bu regimen (70.8%) in the HLA unmatched studies (p<0.00142). The one-year survival in the studies which had HLA-matched donors was 80.56%, which is statistically higher (p<0.001) than the one-year survival in the HLA-unmatched studies (53.96%), indicating a benefit of finding HLA-matched donors. It seems that price and availability could be a factor in the widespread use of Cy.

Antigen-specific blocking of CD4-specific immunological synapse formation using BPI and current therapies for autoimmune diseases

In this review, we discuss T-cell activation, etiology, and the current therapies of autoimmune diseases (i.e., MS, T1D, and RA). T-cells are activated upon interaction with antigen-presenting cells (APC) followed by a "bull's eye"-like formation of the immunological synapse (IS) at the T-cell-APC interface. Although the various disease-modifying therapies developed so far have been shown to modulate the IS and thus help in the management of these diseases, they are also known to present some undesirable side effects. In this study, we describe a novel and selective way to suppress autoimmunity by using a bifunctional peptide inhibitor (BPI). BPI uses an intercellular adhesion molecule-1 (ICAM-1)-binding peptide to target antigenic peptides (e.g., proteolipid peptide, glutamic acid decarboxylase, and type II collagen) to the APC and therefore modulate the immune response. The central hypothesis is that BPI blocks the IS formation by simultaneously binding to major histocompatibility complex-II and ICAM-1 on the APC and selectively alters the activation of T cells from T(H)1 to T(reg) and/or T(H)2 phenotypes, leading to tolerance.

Long-term outcome following hematopoietic stem-cell transplantation in Wiskott-Aldrich syndrome: collaborative study of the European Society for Immunodeficiencies and European Group for Blood and Marrow Transplantation

Wiskott-Aldrich syndrome (WAS) is a rare X-linked immunodeficiency with microthrombocytopenia, eczema, recurrent infections, autoimmune disorders, and malignancies that are life-threatening in the majority of patients. In this long-term, retrospective, multicenter study, we analyzed events that occurred in 96 WAS patients who received transplants between 1979 and 2001 who survived at least 2 years following hematopoietic stem-cell transplantation (HSCT). Events included chronic graft-versus-host disease (cGVHD), autoimmunity, infections, and sequelae of before or after HSCT complications. Three patients (3%) died 2.1 to 21 years following HSCT. Overall 7-year event-free survival rate was 75%. It was lower in recipients of mismatched related donors, also in relation with an older age at HSCT and disease severity. The most striking finding was the observation of cGVHD-independent autoimmunity in 20% of patients strongly associated with a mixed/split chimerism status (P < .001), suggesting that residual-host lymphocytes can mediate autoimmune disease despite the coexistence of donor lymphocytes. Infectious complications (6%) related to splenectomy were also significant and may warrant a more restrictive approach to performing splenectomy in WAS patients. Overall, this study provides the basis for a prospective, standardized, and more in-depth detailed analysis of chimerism and events in long-term follow-up of WAS patients who receive transplants to design better-adapted therapeutic strategies.

Gene frequencies of the HNA-4a and -5a neutrophil antigens in Brazilian persons and a new polymerase chain reaction-restriction fragment length polymorphism method for HNA-5a genotyping

BACKGROUND

The HNA-4a (Mart) and HNA-5a (Ond) antigens are polymorphic variants of alpha(M) (CD11b) and alpha(L) (CD11a) subunits of the beta(2)-integrin, and are associated with single nucleotide polymorphisms (SNP) leading to amino acid dimorphisms. HNA-4a has been linked to alloimmune neonatal neutropenia, but the HNA-5a clinical significance is unclear.

STUDY DESIGN AND METHODS

Using a polymerase chain reaction (PCR) with sequence-specific primers, the frequency of HNA-4a among 121 Brazilian blood donors and 114 Amazon Indians was determined. A PCR-restriction fragment length polymorphism (RFLP) method for HNA-5a genotyping was developed, and the gene frequencies of this antigen were determined among 123 blood donors and 114 Indians. To validate the genotyping method, the amplified DNA from six previously obtained samples (two of each genotype) was sequenced.

RESULTS

The HNA-4a (+/+), HNA-4a (+/-), and HNA-4a (-/-) genotype frequencies of blood donors (0.686, 0.273, 0.041) and Indians (1.000, 0.000, 0.000) were different (p < 0.01). The frequencies of HNA-5a (+/+), HNA-5a (+/-), and HNA-5a (-/-) genotypes among blood donors (0.512, 0.399, 0.089) and Indians (0.746, 0.219, 0.035) also differed (p < 0.01). Sequencing demonstrated concordance with PCR-RFLP genotyping in all six evaluated samples.

CONCLUSION

Comparing to another populations, Brazilians present a higher frequency of HNA-4a-negative allele, suggesting that Brazilians would be more susceptible to HNA-4a alloimmunization. Moreover, the distribution of the HNA-4 alleles observed in Amazon Indians is quite similar to that reported among Koreans. Besides that, a new effective and efficient HNA-5a genotyping technique is now available for population studies.

The role of haploidentical stem cell transplantation in the management of children with haematological disorders

The broader application of stem cell transplantation (SCT) for paediatric diseases has been limited by a lack of human leucocyte antigen (HLA)-matched donors. Virtually all children, however have at least one haploidentical parent who could serve as a donor. Such a donor is immediately available and the considerable costs of additional HLA typing, registry and banking expenditures that are necessary to procure an unrelated donor, could be reduced. Recent technological advances appear to have overcome the historical problems of graft rejection and severe graft versus host disease in the haploidentical setting, and in the latest studies the overall survival for children undergoing haploidentical SCT for leukaemia is now comparable with that following unrelated donor bone marrow or cord blood transplantation. Post-transplant infectious complications and leukaemia relapse remain the most important barriers yet to overcome, and new directions in the use of adoptive cellular immunity appear to be promising in this respect. Haploidentical SCT is now a viable option for those children who do not have an HLA compatible sibling or fully matched unrelated donor. The relative merits of a haploidentical family donor versus mismatched unrelated bone marrow or cord blood donation needs to be assessed in prospective, randomized clinical trials.

Leukocyte depletion attenuates expression of neutrophil adhesion molecules during cardiopulmonary bypass in human beings

BACKGROUND

On the basis of scanty information, the effects of a leukocyte filter during cardiac operations in human beings have been examined from the viewpoint of the expression of neutrophil adhesion molecules. This study was therefore designed to determine whether leukocyte depletion during cardiopulmonary bypass may interfere with neutrophil adhesion properties.

METHODS

Twenty-four patients undergoing elective heart operations were randomly allocated to a leukocyte-depletion group or a control group. Blood samples were collected at 7 points: before sternotomy, at 10, 30, and 60 minutes of cardiopulmonary bypass, at termination of cardiopulmonary bypass, 5 minutes after protamine administration, and 2 hours after cardiopulmonary bypass. The expression of the neutrophil surface adhesion molecules L-selectin and beta2-integrins was determined by flow cytometric analysis in whole blood.

RESULTS

(1) CD11a expression did not change significantly in either group. There were no significant differences between control and leukocyte-depletion groups (P =.63). (2) There was a significantly higher expression of CD11b on the neutrophils during cardiopulmonary bypass in the control group than in the leukocyte-depletion group (P =.01). (3) CD11c expression was initially up-regulated from the onset of cardiopulmonary bypass, reaching a peak at 60 minutes after bypass in the control group (P =.02). The expression of CD11c did not differ significantly between groups (P =.23). (4) L-selectin expression was significantly lower in the leukocyte-depletion group than in the control group (P =.03).

CONCLUSIONS

The major findings of the present study in human subjects undergoing elective cardiac operations with cardiopulmonary bypass are as follows: (1) bypass was associated with an up-regulation of the adhesion molecules L-selectin, CD11b, and CD11c but with no significant change in CD11a expression, and (2) the clinical use of a leukocyte-depleting filter could down-regulate the expression of CD11b and L-selectin.

Mechanisms of tolerance induction: blockade of co-stimulation

Induction of tolerance to transplantation antigens is believed to be a promising way to achieve long-term allograft survival without a deleterious immunosuppressive regimen. T-cell activation, which is an essential feature of graft rejection, requires a first signal provided by T-cell receptor (TCR) ligation and a second signal provided by engagement of co-stimulatory molecules with their respective ligands on antigen-presenting cells. The coordinated triggering of these two independent signalling systems ensures the full T-cell activation, including proliferation and acquisition of effector function. TCR occupancy in the absence of co-stimulatory signals leads to a sustained loss of antigen responsiveness called clonal anergy, which could be of major importance in transplantation. In vivo, co-stimulation blockade was indeed shown to allow for long-term allograft survival in several transplantation models. However, the current continuous identification of new co-stimulatory molecules suggests that a functional redundancy of the system exists and that tolerance to transplantation antigens might be achieved more easily through the combined blockade of two or several co-stimulatory signals. In this review, we analyse the biological effects of the disruption of some co-stimulation pathways in vitro and in vivo and discuss their potential interest for tolerance induction.

Genetically haploidentical stem cell transplantation for acute leukemia

Genetically haploidentical stem cell transplants have been performed for several decades, mostly for patients with advanced acute leukemia. Such transplants are an option for those patients who do not have a histocompatible sibling donor. The historical data have been disappointing due to graft-versus-host disease, engraftment failure and delayed immune reconstitution. Recent modifications and new technological developments have led to more encouraging clinical results. Haploidentical transplantation is immediately available to the majority of patients with acute leukemia and is an acceptable alternative to matched unrelated donor transplantation.

Proteasome activity is required for T lymphocyte aggregation after mitogen activation

The proteasome is a multicatalytic complex of proteases involved in T lymphocyte proliferation and activation through multiple mechanisms. In this study, we investigated its role in lymphocyte aggregation. We found that blocking proteasome activity by a proteasome-specific inhibitor lactacystin (LAC) prevented clustering of T lymphocytes after stimulation with various mitogens. Expression of adhesion molecules ICAM-1 and LFA-1 at cell surfaces of activated T cells was decreased after treatment with LAC. Mechanisms by which the proteasome intervenes in the expression of these adhesion molecules were different. LAC inhibited ICAM-1 expression at the mRNA level, whereas LFA-1 inhibition was probably at a post-translational level. Downregulation of these molecules after proteasome inhibition likely contributes to the observed repression of T cell aggregation. Our results show that the proteasome plays an important role in cell-cell interaction during T cell activation.

Haploidentical transplantation

When allogeneic transplant is indicated and a MSD is not available, most centers first seek an unrelated donor. However, one must avoid undue delays when a donor is not available and family members should be typed to identify the preferred donor amongst the family. Since a family donor can provide access to transplant for almost every patient, a greater effort should be encouraged to improve and expand haploidentical transplantation. The advantages, outlined in Table 1, suggest compelling reason to perfect the use of haploidentical related donors.

Improved long-term results with thymoglobuline induction therapy after cardiac transplantation: a comparison of two different rabbit-antithymocyte globulines

BACKGROUND

The aim of this retrospective single center analysis was to compare possible long-term benefits of two different rabbit-antithymocyte globuline (ATG) induction therapies after cardiac transplantation.

PATIENTS AND METHODS

A total of 484 primary cardiac transplanted patients received induction therapy with two different rabbit-ATGs (thymoglobuline: n=342, ATG-fresenius: n=142). All patients received immunosuppressive maintenance therapy with cyclosporine, azathioprine, and prednisolone. Cardiac rejection was assessed by serial endomyocardial biopsies. Surveillance of graft arteriosclerosis was performed by angiograms 1, 3, and 5 years after transplantation.

RESULTS

Five-year survival was significantly better in the thymoglobuline group (76 vs. 60%). Thymoglobuline patients had a lower rate of death from rejection (2.3 vs. 10%; P<0.01) and graft arteriosclerosis (0.88 vs. 5.6%; P<0.01). After 5 years, freedom from rejection was 72% in the thymoglobuline group compared to 42% in the ATG-fresenius group (P<0.01). Graft arteriosclerosis appeared in 14% of thymoglobuline patients and in 28% of ATG-fresenius patients (P<0.01). Viral infections occurred more often in thymoglobuline patients (53 vs. 39%, P<0.05) although there was no difference in appearance of cytomegalovirus disease (17 vs. 13%). Freedom from posttransplant malignant disease was comparable between the two groups.

CONCLUSION

These results suggest that there are differences between rabbit ATG products. The superior prevention of rejection with thymoglobuline may be the reason for the lower rate of graft arteriosclerosis.

Immune-adhesion molecules in the prevention of allograft rejection and reperfusion injury

Control of the immune system is of indispensable importance for graft acceptance and function. Immunological changes in the graft before and after organ harvesting, the transplantation procedure itself and the organ recipients clinical state contribute to the immune response. Leukocyte trafficking [1] into a graft is regulated by various signal transducing molecules, which have been characterised during the past years. Ligand molecules on endothelial cells and in the organ parenchyma are the counterparts for leukocyte adhesion and tissue infiltration. The expression of these ligand molecules is regulated by soluble factors and cell-cell interactions [2]. The regulation of tissue inflammation and repair mechanisms involving components of the immune system therefore depends on a number of cell-surface interactions. The processes of intravascular adhesion, transmigration and infiltration by leukocytes and platelets are mainly mediated by receptor ligand interactions with target cells (cell-cell) and extracellular matrix proteins (cell-matrix). The main molecular families of adhesion receptor/ligand molecules have been identified. Today, we are still far from understanding this network of interactions. The numbers of molecules and factors involved are still increasing. This review summarises the currently available knowledge on the intervention in this system by monoclonal antibodies (mAbs), peptides and blocking agents. From this review, it is evident that further investigations are justified.

Effect of anti-LFA-1 monoclonal antibody on rat small bowel allograft survival and circulating leukocyte populations

Anti-LFA-1 monoclonal antibodies (mAb) prolong graft survival in several animal models. This study assessed the effect of an anti-LFA-1 mAb (WT.1) on small bowel allograft rejection, circulating leukocyte subsets and in vivo target cell antigen blockade. Heterotopic small bowel transplantation was performed between PVG donor and DA recipient rats. Transplanted animals received 1 mg/kg per day WT.1 on days -1, 0 (day of transplantation) and 1. Three doses of WT.1 were also administered to a group of untransplanted animals to monitor circulating leukocyte populations and in vivo binding. WT.1 prolonged recipient survival from 7 to 14 days. Peripheral leukocyte counts increased more than twofold, primarily due to marked increases in both CD4+ and CD8+ lymphocytes. Approximately 85% of WT.1 binding sites on lymphocytes and monocytes were blocked/modulated after the course of therapy. WT.1 has marked effects on circulating leukocytes and target cell binding capacities and can affect the survival of rat small bowel transplant recipients.

Treatment of Familial Hemophagocytic Lymphohistiocytosis With Bone Marrow Transplantation From HLA Genetically Nonidentical Donors

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare genetic disorder associated with the onset early in life of overwhelming activation of T lymphocytes and macrophages invariably leading to death. Allogeneic bone marrow transplantation (BMT) from an HLA-identical related donor is the treatment of choice in patients with this disease. However, fewer than 20% of patients have a disease-free HLA-identical sibling. BMT from HLA-nonidentical related donors has previously met with poor results, with graft rejection a major obstacle in all cases. We describe BMTs from HLA-nonidentical related donors (n = 13) and from a matched unrelated donor (n = 1) performed in two centers in 14 consecutive cases of FHL. Remission of disease was achieved before BMT in 10 patients. Marrow was T-cell–depleted to minimize graft-versus-host disease (GVHD). Antiadhesion antibodies specific for the α chain of the leukocyte function–associated antigen-1 (LFA-1, CD11a) and the CD2 molecules were infused pre-BMT and post-BMT to help prevent graft rejection, in addition to a conditioning regimen of busulfan (BU), cyclophosphamide (CP), and etoposide (VP16) or antithymocyte globulin (ATG). Sustained engraftment was obtained in 11 of 17 transplants (3 patients had 2 transplants) and disease-free survival in 9 patients with a follow-up period of 8 to 69 months (mean, 33). Acute GVHD greater than stage I was not observed, and 1 patient had mild cutaneous chronic GVHD that resolved. Toxicity due to the BMT procedure was low. Results obtained using this protocol are promising in terms of engraftment and event-free survival within the limitations of the small sample. We conclude that an immunologic approach in terms of drugs used to obtain disease remission and a conditioning regimen that includes antiadhesion molecules in T-cell–depleted BMT from HLA genetically nonidentical donors is an alternative treatment that warrants further study in FHL patients who lack a suitable HLA genetically identical donor.

Treatment of Familial Hemophagocytic Lymphohistiocytosis With Bone Marrow Transplantation From HLA Genetically Nonidentical Donors

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare genetic disorder associated with the onset early in life of overwhelming activation of T lymphocytes and macrophages invariably leading to death. Allogeneic bone marrow transplantation (BMT) from an HLA-identical related donor is the treatment of choice in patients with this disease. However, fewer than 20% of patients have a disease-free HLA-identical sibling. BMT from HLA-nonidentical related donors has previously met with poor results, with graft rejection a major obstacle in all cases. We describe BMTs from HLA-nonidentical related donors (n = 13) and from a matched unrelated donor (n = 1) performed in two centers in 14 consecutive cases of FHL. Remission of disease was achieved before BMT in 10 patients. Marrow was T-cell–depleted to minimize graft-versus-host disease (GVHD). Antiadhesion antibodies specific for the α chain of the leukocyte function–associated antigen-1 (LFA-1, CD11a) and the CD2 molecules were infused pre-BMT and post-BMT to help prevent graft rejection, in addition to a conditioning regimen of busulfan (BU), cyclophosphamide (CP), and etoposide (VP16) or antithymocyte globulin (ATG). Sustained engraftment was obtained in 11 of 17 transplants (3 patients had 2 transplants) and disease-free survival in 9 patients with a follow-up period of 8 to 69 months (mean, 33). Acute GVHD greater than stage I was not observed, and 1 patient had mild cutaneous chronic GVHD that resolved. Toxicity due to the BMT procedure was low. Results obtained using this protocol are promising in terms of engraftment and event-free survival within the limitations of the small sample. We conclude that an immunologic approach in terms of drugs used to obtain disease remission and a conditioning regimen that includes antiadhesion molecules in T-cell–depleted BMT from HLA genetically nonidentical donors is an alternative treatment that warrants further study in FHL patients who lack a suitable HLA genetically identical donor.

Correction of Fas (CD95) deficiency by haploidentical bone marrow transplantation

Recently, an inherited syndrome characterized by nonmalignant lymphoproliferation with autoimmune manifestations, caused by mutations of the Fas (CD95) receptor gene has been described. Because of disease severity, i.e. unremitting lymphoproliferation in a child with complete Fas deficiency, a haploidentical bone marrow transplantation (BMT) was performed despite the known resistance of Fas-deficient lpr mice to bone marrow transplantation. Marrow graft was rejected early; however, a second attempt using bone marrow from the mother led to engraftment and to control of lymphoproliferation and of autoimmune thrombocytopenia up to the last follow-up at 24 months after BMT. This single case shows that resistance to bone marrow engraftment caused by survival of Fas-deficient cells can be overcome.

Specific immunosuppression of corneal allograft rejection by combination of anti-VLA-4 and anti-LFA-1 monoclonal antibodies in mice

It has been reported that allograft rejection is mediated by a variety of adhesion molecules. Using a corneal allograft model in mice, we studied the role of very late antigen (VLA)-4 and leukocyte function-associated antigen (LFA)-1 adhesion molecules in corneal allograft rejection and the effects of monoclonal antibodies (mAbs) to them in suppressing corneal rejection. C3H/He donor corneas were transplanted into BALB/c corneal beds. The allografted mice were treated with a control mAb (M18/2), mAbs to VLA-4, or LFA-1 or their combination by i.p. injection until day 7. The expression of VLA-4, LFA-1, major histocompatibility complex (MHC) class II antigens, interleukin (IL)-2, IL-2 receptor and interferon gamma (IFNgamma) in the grafted cornea were studied immunohistochemically. Cytotoxic T lymphocyte (CTL) responses to donor alloantigens were assessed. The skins from a syngeneic donor or a third-part strain were transplanted 8 weeks after the initial keratoplasty onto the mice treated with anti-LFA-1 plus anti-VLA-4 mAbs. Fourteen of 16 allografts in non-treated mice and control mAb-treated mice became opaque by 2 weeks after transplantation. At 2 weeks, non-treated allografts showed expression of MHC class II antigens on keratocytes and mononuclear cells at the host-graft junction. Also, mononuclear cells expressing VLA-4, LFA-1, IL-2, IL-2 receptor and IFNgammawere present in the stroma at the host-graft junction. The allografts treated with either anti-VLA-4 or anti-LFA-1 alone, or anti-VLA-4 plus anti-LFA-1 remained transparent for more than 2 weeks, and the survival rates at 14 weeks was 0%, 16.7%, and 75.0%, respectively. The combined use of anti-VLA-4 and anti-LFA-1 mAbs prolonged graft survival significantly (P<0.05) at 14 weeks as compared with anti-LFA-1 mAb alone. At 3 weeks, CTL responses to donor alloantigens were depressed in mice treated with either anti-LFA-1 alone or anti-LFA-1 plus anti-VLA-4. Specific prolongation of donor-syngeneic skin was observed after treatment with the combination of these two mAbs. These results indicate that VLA-4 and LFA-1 have important roles in rejection process of corneal allografts, and that the combined use of mAbs to these molecules has remarkable effects on inducing alloantigen-specific immunosuppression in corneal transplantation.

Will tolerance become a clinical reality?

The goal of transplant physicians is to create a state of antigen-specific tolerance in the recipient, whereby the graft is not rejected and the patient will not need a lifetime of medical therapy. Although the immunosuppressive medications used are effective in lowering the incidence of rejection, they produce significant side effects and do not induce a state of transplantation tolerance. Progress toward inducing transplantation tolerance has been made in animal models, primarily by the exploitation of the natural mechanisms that vertebrates have to maintain self-tolerance. These same strategies are being employed in clinical trials and consequently are promising and challenging for the future.

Folding of the beta-propeller domain of the integrin alphaL subunit is independent of the I domain and dependent on the beta2 subunit

We have studied the folding during biosynthesis of the lymphocyte function-associated antigen 1 (LFA-1) alphaL subunit using mAb to epitopes that map to seven different regions within the amino acid sequence. The N-terminal portion of alphaL is predicted to contain a beta-propeller domain, consisting of seven beta-sheets, and an I domain that is predicted to be inserted between beta-sheet 2 and beta-sheet 3 of the beta-propeller. The I domain of alphaL folds before association with the beta2 subunit, as shown by immunoprecipitation of the unassociated alphaL subunit by mAbs specific for four different sequence elements within the I domain. By contrast, the beta-propeller domain is not folded in unassociated alphaL after a chase of as long as 12 h after synthesis, but does fold upon association with beta2. This is shown with mAbs to regions of alphaL, that precede and follow the I domain in the primary structure. A mAb that maps near the junction of the C terminus of the I domain with the beta-propeller domain suggests that this region is partially folded before subunit association. The results show that the I domain and beta-propeller domains fold independently of one another, and suggest that the beta-propeller domain bears an interface for association with the beta subunit.

A randomized multicenter trial comparing leukocyte function-associated antigen-1 monoclonal antibody with rabbit antithymocyte globulin as induction treatment in first kidney transplantations

Adhesion molecules are involved in several steps in the immune response: leukocyte adhesion to the endothelium, transendothelial migration, cooperation between immunocompetent cells, and cytotoxicity. Leukocyte function-associated antigen-1 plays a central role among adhesion molecules. In a multicenter randomized open trial, we compared a monoclonal antibody directed against the alpha chain of LFA-1 (Oduli-momab; IMTIX/Pasteur Mérieux Sérums et Vaccins) with rabbit antithymocyte globulin (rATG; IMTIX/Pasteur Mérieux Sérums et Vaccins), as part of a quadruple sequential protocol in 101 patients receiving a first kidney transplant. Clinical tolerance of anti-LFA-1 mAb was better than that of rATG. Short-term rejection rates (< 15 days) were not significantly different (15% and 16% for anti-LFA-1 mAb and rATG, respectively). However, 11% of the anti-LFA-1 mAb patients experienced rejection during the first 10 days of the treatment course compared with none of the patients treated with rATG. The incidence and severity of acute rejection in the first 3 months was not significantly different between groups. Of the LFA-1 and rATG patients, 96% and 92% of the grafts, respectively, were functioning at 12 months. The incidence and severity of infection, whatever the origin, were comparable in both groups. In addition, it was observed that fewer patients required posttransplantation dialysis in the anti-LFA-1 mAb group (19%, vs. 35% for rATG), although the difference was not statistically significant. Altogether, the beneficial action of this monoclonal antibody on short-term renal function recovery makes it a useful tool in the management of renal patients undergoing kidney transplantation.

Experimental antileukocyte interventions in cerebral ischemia

White blood cells (WBCs) play vital roles in host defense. Recently, increasing interest has been directed toward the question of whether WBCs, particularly polymorphonuclear leukocytes, could also act as mediators of secondary brain damage in the setting of focal and global cerebral ischemia with and without reperfusion. Considerable insight into the importance of WBC-mediated tissue injury has been gained from studies employing antileukocyte interventions in experimental cerebral ischemia. The purpose of this article is to survey the different approaches taken to interfere with WBC inflammatory function. Emphasis is laid on a discussion of the efficacy of these interventions, their effects and side effects on cerebral and systemic parameters, and the power of evidence they provide for identification of WBCs as important factors in cerebral ischemia. The role of WBCs has been investigated in a great variety of global and focal cerebral ischemia models with and without reperfusion, leading to sometimes contradictory results. In the light of currently available data, it seems likely that WBCs contribute to secondary brain damage in the scenario of experimental transient focal cerebral ischemia, if the insult is not too severe.

Aspects concerning busulfan pharmacokinetics and bioavailability

Busulfan as a high-dose therapy is an important component of many of the myeloablative regimens for both allogeneic and autologous bone marrow transplantation (BMT) in adults and children. During the last decade, several studies have shown a wide inter- and intra-patient variability of busulfan disposition in adults and children. Some of the factors affecting the interpatient-variability were identified as circadian rhythmicity, age, disease, drug interaction, alteration in hepatic function and recently busulfan bioavailability. In adults, pharmacodynamic studies have shown a positive correlation between high-systemic exposure of the drug and venocclusive disease (VOD). However, pharmacodynamic studies in children did not establish any correlation between the systemic exposure and VOD. Drug-monitoring and dose adjustment in adults were used successfully to decrease the occurrence of VOD and mortality. It was observed that about 20% of the busulfan dose crosses the blood brain barrier. The high amount of the drug which enters the brain can probably be involved in the CNS toxicities reported. In children, a low rate of toxicity combined with a high rate of engraftment failure were observed. Several investigators have expressed their concern about the dosage in children and many suggested higher doses based on the body surface area for young children. However, recently it was shown that busulfan bioavailability varied by 2-fold in adults (0.5-1.03) while in children a 6-fold variation was observed (0.22-1.20). The access to an intravenous form of busulfan and a deeper understanding of pharmacodynamics of the drug might be essential to optimize the treatment, reach a successful engraftment and lower the therapy related toxicities.

Bone marrow transplantation in 26 patients with Wiskott-Aldrich syndrome from a single center

We retrospectively analyzed the outcome of bone marrow transplantation (BMT) performed in 26 patients with Wiskott-Aldrich syndrome (WAS) in one center. Twenty-eight transplantation procedures were performed. Ten unselected patients received unmanipulated marrow from a donor with genetically identical human leukocyte antigen (HLA). Eight patients were cured and survive 1.5 to 16.5 years after BMT. One patient successfully received a T-cell-depleted marrow from a matched unrelated donor. Sixteen patients were selected to receive a related HLA partially incompatible BMT because of the occurrence of life-threatening complications from the WAS (i.e., refractory thrombocytopenia, autoimmunity including vasculitis and sepsis). All but one received T-cell-depleted marrow after a conditioning regimen of busulfan and cyclophosphamide. One patient had two BMTs. Engraftment occurred in 12 of 17 attempts. The addition of monoclonal antibodies to lymphocyte function-associated antigen-1 and CD2 molecules appeared to improve engraftment. Six patients were long-term survivors, whereas others died of viral infections (n = 7), among which Epstein-Barr virus-induced B-lymphocyte proliferative disorder was predominant. Delay in development of full T- and B-cell functions accounted for severe infectious complications. These results confirm the excellent outcome of HLA genetically identical BMT in WAS, whereas BMT from HLA partially incompatible donors should be strictly restricted to patients with severe complications of WAS.

Drug-induced in vitro inhibition of neutrophil-endothelial cell adhesion

1. Leukocyte-endothelial cell interactions play an important role during ischaemia-reperfusion events. Adhesion molecules are specifically implicated in this interaction process. 2. Since defibrotide has been shown to be an efficient drug in reducing damage due to ischaemia-reperfusion in many experimental models, we analysed the effect of defibrotide in vitro on leukocyte adhesion to endothelial cells in basal conditions and after their stimulation. 3. In basal conditions, defibrotide (1000 micrograms ml-1) partially inhibited leukocyte adhesion to endothelial cells by 17.3% +/- 3.6 (P < 0.05), and after endothelial cell stimulation (TNF-alpha, 500 u ml-1) or after leukocyte stimulation (fMLP, 10(-7) M), it inhibited leukocyte adhesion by 26.5% +/- 3.4 and 32.4% +/- 1.8, respectively (P < 0.05). 4. In adhesion blockage experiments, the use of the monoclonal antibody anti-CD31 (5 micrograms ml-1) did not demonstrate a significant inhibitory effect whereas use of the monoclonal antibody anti-LFA-1 (5 micrograms ml-1) significantly interfered with the effect of defibrotide. 5. This result was confirmed in NIH/3T3-ICAM-1 transfected cells. 6. We conclude that defibrotide is able to interfere with leukocyte adhesion to endothelial cells mainly in activated conditions and that the ICAM-1/LFA-1 adhesion system is involved in the defibrotide mechanism of action.

Ibuprofen inhibits pyrogen-dependent expression of VCAM-1 and ICAM-1 on human endothelial cells

Leukocyte adhesion and transmigration through the endothelial cell (EC) layer plays a crucial role in inflammation. IL-1 alpha and TNF alpha increase EC-adhesiveness for leukocytes by stimulating surface expression of ICAM-1 (intercellular adhesion molecule 1, CD54), VCAM-1 (vascular cell adhesion molecule 1, CD106) and E-selectin (CD62E). In this study, the effects of ibuprofen on IL-1 alpha and TNF alpha-induced expression of ICAM-1, VCAM-1 and E-selectin on cultured human umbilical vein EC (HUVEC) were analyzed. Exposure to IL-1 alpha or TNF alpha resulted in an increased expression of VCAM-1, ICAM-1, and E-selectin. Ibuprofen was identified as a potent inhibitor of IL-1 alpha and TNF alpha-induced surface expression of VCAM-1 and a less potent inhibitor of pyrogen-induced expression of ICAM-1, whereas no effect on E-selectin was found. The effects of ibuprofen on VCAM-1 expression were dose-dependent (IC50 [IL-1 alpha]: 0.5 mM; IC50 [TNF alpha]: 0.5 mM) and time-dependent with maximum responses observed after 18 h. Moreover, ibuprofen abrogated pyrogen-dependent adhesion of leukocytes to HUVEC. Ibuprofen also inhibited VCAM-1 mRNA expression in pyrogen activated EC. VCAM-1-downregulation on EC by ibuprofen may contribute to the anti-inflammatory actions of the drug.

Specific acceptance of fetal bowel allograft in mice after combined treatment with anti-intercellular adhesion molecule-1 and leukocyte function-associated antigen-1 antibodies

OBJECTIVE

The aim of this study was to see whether tolerance could be induced by simultaneous administration of monoclonal antibodies (MoAbs) to intercellular adhesion molecule-1 (ICAM-1) and leukocyte function-associated antigen-1 (LFA-1) after transplantation of fetal small bowel between fully incompatible mice strains.

METHODS

Fetal small bowel from either BALB/c (H-2d) or C3H/He (H-2k) mice was transplanted into the space between the peritoneum and rectus abdominis of adult C3H/He recipient mice. Syngeneic (n = 6) and two allogeneic transplant groups were made. In one of the allogeneic groups (n = 8), no immunosuppressant was given. In the other allogeneic group (n = 13), both anti-LFA-1 and anti-ICAM-1 MoAbs (50 micrograms each/mouse/day) were given intraperitoneally after transplantation for the first 4 weeks. In the syngeneic and untreated allogeneic groups, all mice were killed 4 weeks after transplantation. In the treated allogeneic group, eight mice were killed 6 weeks after cessation of the MoAb treatment. At the time the mice were killed, the bowel graft as well as the recipient spleen were taken for histologic analysis and cytotoxic T-lymphocyte (CTL) assay, respectively. Each mouse in the remaining treated five mice was transplanted with BALB/c and C57BL/6 (as third-party) full-thickness skin simultaneously 8 weeks after cessation of the MoAb treatment.

RESULTS

All grafts in the syngeneic group survived with normally developing villi, whereas all grafts in the untreated allogeneic group disappeared. In the treated allogeneic group, all allografts developed normal mucosa without any sign of rejection. Splenocytes from the recipient mice in the untreated allogeneic group showed increased CTL induction against donor-type alloantigen (p < 0.005), compared with that in the syngeneic group. Suppressed CTL induction against donor-type alloantigen was observed in the treated allografted recipient (p < 0.001), whereas CTL induction against third-party alloantigen was intact (p = NS). Third-party skin graft was normally rejected within 10 days, whereas donor-type skin graft was accepted in all mice tested.

CONCLUSIONS

Specific tolerance for fetal bowel allografts could be induced by a relatively short-term treatment with anti-ICAM-1 and anti-LFA-1 MoAbs. This mode of immunointervention could perhaps be applied to humans undergoing small-bowel transplantation.

A binding interface on the I domain of lymphocyte function-associated antigen-1 (LFA-1) required for specific interaction with intercellular adhesion molecule 1 (ICAM-1)

Previous studies have shown that lymphocyte function-associated antigen-1 (LFA-1) molecules containing the human alpha (CD11a) and human beta (CD18) subunits but not the murine alpha and human beta subunits can bind to human intercellular adhesion molecule 1 (ICAM-1). Using human/mouse LFA-1 alpha subunit chimeras, we mapped regions required for binding to ICAM-1 N-terminal to amino acid (aa) residue 350. Ligand binding sites were mapped in greater detail by scanning this region with murine sequences from 56 down to 17 aa in length and finally by introducing single or few murine aa residue replacements into the human sequence. Replacement of two non-contiguous regions of aa residues 119-153 and 218-248 in the me domain with the corresponding mouse sequences abolished most binding to human ICAM-1, without affecting alpha beta subunit association or expression on the surface of transfected COS cells. Specific residues within the I domain found to be important were Met-140, Glu-146, Thr-243, and Ser-245. Using the recently solved structure of the Mac-1 (CD11b) I domain as a model (Lee, J.-O., Rieu, P., Arnaout, M.A., and Liddington, R. (1995) Cell 80, 631-638), these residues are shown to be located on the surface of the I domain surrounding the site to which Mg2+ is chelated, and fine a ligand binding interface. Mapping of the epitopes of a panel of mouse anti-human and rat anti-mouse monoclonal antibodies gave concordant results. Epitopes were mapped to two different regions in the N-terminal domain, four regions within the I domain, and two regions between the I domain and the EF hand-like repeats. Monoclonal antibodies to epitopes within the mid- to C-terminal portion of the I domain and the N-terminal portion of the region between the I domain and the EF hand-like repeats gave good inhibition of LFA-1-dependent homotypic aggregation with cells that express either ICAM-1 or ICAM-3 as the major LFA-1 ligand.

Anti-leukocyte function-1 antibody treatment prevents the rejection of intraocular regressor tumors and their metastases

The role of the cell adhesion molecules, LFA-1 and ICAM-1, in intraocular tumor rejection was examined using four different syngeneic intraocular regressor tumors and four different inbred mouse strains. All four tumors undergo T cell-dependent immune rejection in the syngeneic host. Two of the tumors, D5.1G4 melanoma and P91 mastocytoma, undergo rejection by a cytotoxic T lymphocyte-like immune process. The other two tumors, UV5C25 fibrosarcoma and 124E2 melanoma, are rejected by a process that appears to be mediated by delayed-type hypersensitivity. Systemic administration of anti-LFA-1 prevented the rejection of all four categories of tumors. By contrast, similar in vivo treatment with anti-ICAM-1 antibody did not inhibit tumor rejection. The effect of anti-LFA-1 and anti-ICAM-1 antibody treatment on the rejection of metastases arising from intraocular P91 tumors was also examined and found to be highly dependent upon normal LFA-1 function since antibody treatment with anti-LFA-1 prevented the rejection of metastases. Treatment with anti-ICAM-1 antibody alone had no appreciable effect on the rejection of metastases. The results from this study indicate that the expression and function of LFA-1 is crucial for the generation of immune responses to tumor antigens originating within the eye and the expression of tumor immunity within the eye and at distant sites.

Prevention of fetal bowel allograft rejection by combined treatment with anti-ICAM-1 and anti-LFA-1 antibodies

Prevention and treatment of allograft rejection remain the major issues in clinical small bowel transplantation. New strategies for manipulating immune responses using more powerful immunosuppressive agents continue to be evaluated. The fetal small bowel from BALB/c (H-2d) or C3H/He (H-2k) mice was transplanted into the space between the peritoneum and rectus abdominis of adult C3H/He (H-2k) recipient mice. Syngeneic (n = 6) and allogeneic transplant groups were made. In the allogeneic group, the recipient mice were subdivided into three groups, depending on the duration of combined treatment with anti-LFA-1 and anti-ICAM-1 monoclonal antibodies (MAbs): untreated (n = 10), 7-day course (n = 10), and 4-week course (n = 14). A dose of 50 micrograms/mouse/d each of both MAbs was given intraperitoneally, immediately after transplantation and on the consecutive days. All mice were killed 4 weeks after transplantation, and the graft as well as the recipient spleen were taken for histological examination, graft survival ratio, mixed lymphocyte reaction (MLR) assay and cytotoxic T lymphocyte (CTL) assay. All grafts in the syngeneic group survived with normal villi, whereas all grafts in the allogeneic group without treatment disappeared within 4 weeks. All grafts in the allogeneic group with a 7-day course of MAb treatment showed marked disruption of the mucosa with massive cellular infiltration. However, in the allogeneic group treated for 4 weeks, all allografts had adequate growth and demonstrated normal villi with minimal cellular infiltration. Splenocytes from allografted recipient mice without MAb treatment showed markedly increased MLR and CTL activity, compared with the activity seen in the syngeneic MLR and CTL.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of proton magnetic resonance spectroscopy of blood serum as a diagnostic tool in bone marrow transplantation

The use of proton high-resolution magnetic resonance spectroscopy (MRS) allows the rapid detection and quantitation of modification in the blood serum metabolic profiles in haematooncological patients. This study examines the feasibility of using proton MRS as a diagnostic tool in predicting the outcome of bone marrow transplantation (BMT) at the earliest possible date. Proton spectra of serum samples from 18 BMT patients (11 autologous-BMT and seven allogeneic-BMT), six hematooncological patients that did not undergo BMT and six normal individuals were recorded at 400 MHz. A longitudinal MRS study was carried for these groups and the data were evaluated for statistical significance. It was determined that the MRS results, taken at different time points before and after the BMT treatment, are statistically significant. However, no significant difference was observed in the MRS parameters between the transplanted patients and the control patients. We could not obtain significant correlation between the MRS results and the immunoglobulin level, engraftment parameters or the age, sex, stage of basic disease, conditioning protocols, transplant type, post transplant complications (including death) and outcome.

Adhesion to human neurons and astrocytes of monocytes: the role of interaction of CR3 and ICAM-1 and modulation by cytokines

Monocytes but not unstimulated lymphocytes adhered to human neurons and astrocytes in primary culture, as demonstrated by double labeling. The expression of VCAM-1 was higher on neurons than on astrocytes, whereas that of beta 1, alpha 1, alpha 2, alpha 4 and alpha 5 chains from the integrins and of ICAM-1 was identical on both types of cells. The expression on neurons of ICAM-1, but not of integrins, was up-regulated by exogenous tumor necrosis factor (TNF) alpha, interleukin (IL)-1 alpha and interferon (IFN)-gamma. The same was observed on astrocytes associated with a sharp increase in the expression of VCAM-1. Adhesion between monocytes and neurons or astrocytes was 80% inhibited by mAbs directed against the CR3 determinant on monocytes or against ICAM-1 on neural cells but not by any of the other mAbs against adhesion proteins that were tested. Finally, the level of endogenous production of IL-1 alpha and TNF alpha was greatly increased after the adhesion of monocytes to CNS cells.

Monoclonal antibodies against ICAM-1 and LFA-1 prolong nerve allograft survival

In a rat nerve allograft model, specific immunosuppression was approached with monoclonal antibodies (MAbs) against cell-surface molecules. After engraftment, recipients were treated with antiintercellular adhesion molecule-1 (ICAM-1) and antilymphocyte function-associated antigen-1 (LFA-1) MAbs for 14 days. Functional recovery was evaluated biweekly. Electrophysiological and histological assessments were performed at 6 and 16 weeks. Immunologic responsiveness in the recipients was assessed with a cytotoxic T lymphocyte (CTL) assay at 16 weeks and skin grafts at 18 weeks. The untreated allograft group demonstrated complete disruption of fascicular architecture with poor nerve regeneration. The MAb-treated allografts maintained well-organized nerve architecture with a dense population of well-myelinated fibers. These animals showed functional and electrophysiological recovery. Suppression of CTL activity was nerve donor specific and the survival time of nerve donor skin grafts was prolonged, suggesting induction of alloantigen-specific tolerance. MAbs therapy directed against ICAM-1/LFA-1 presents a new approach for the management of the peripheral nerve allograft response.

Immunosuppressive effect of monoclonal antibodies to ICAM-1 and LFA-1 on peripheral nerve allograft in mice

This study evaluated the immunosuppressive effect of monoclonal antibodies against cell surface molecules in a murine peripheral nerve allograft model. After nerve allografting, 18 recipients were treated with both anti-intercellular adhesion molecule-1 (ICAM-1) and anti-lymphocyte function-associated molecule-1 (LFA-1) monoclonal antibodies in low or high dose. Nerve allografts were harvested at 8 weeks for histologic and morphometric evaluation. Recipients were subsequently challenged with skin grafts at 9 weeks and a cytotoxic assay at 12 weeks. The majority of the antibody-treated allografts (13 of 18) showed excellent regeneration comparable to the autografts with preservation of the normal nerve architecture and scant cellular infiltrate. All untreated allografts demonstrated severe structural disorganization with cellular infiltrate consistent with acute rejection. In the high dose group, the mean skin graft survival time from nerve donor mice, but not third-party mice, was significantly prolonged. (17.5 vs. 11.3 days). Similarly, the cytotoxic activity against nerve donor alloantigen was significantly suppressed. These preliminary findings suggest that antibody therapy alone can facilitate nerve regeneration in a murine nerve allograft model.

Transient immunosuppressive treatment leads to long-term retention of allogeneic myoblasts in hybrid myofibers

Normal and genetically engineered skeletal muscle cells (myoblasts) show promise as drug delivery vehicles and as therapeutic agents for treating muscle degeneration in muscular dystrophies. A limitation is the immune response of the host to the transplanted cells. Allogeneic myoblasts are rapidly rejected unless immunosuppressants are administered. However, continuous immunosuppression is associated with significant toxic side effects. Here we test whether immunosuppressive treatment, administered only transiently after allogeneic myoblast transplantation, allows the long-term survival of the transplanted cells in mice. Two immunosuppressive treatments with different modes of action were used: (a) cyclosporine A (CSA); and (b) monoclonal antibodies to intracellular adhesion molecule-1 and leukocyte function-associated molecule-1. The use of myoblasts genetically engineered to express beta-galactosidase allowed quantitation of the survival of allogeneic myoblasts at different times after cessation of the immunosuppressive treatments. Without host immunosuppression, allogeneic myoblasts were rejected from all host strains tested, although the relative time course differed as expected for low and high responder strains. The allogeneic myoblasts initially fused with host myofibers, but these hybrid cells were later destroyed by the massive immunological response of the host. However, transient immunosuppressive treatment prevented the hybrid myofiber destruction and led to their long-term retention. Even four months after the cessation of treatment, the hybrid myofibers persisted and no inflammatory infiltrate was present in the tissue. Such long-term survival indicates that transient immunosuppression may greatly increase the utility of myoblast transplantation as a therapeutic approach to the treatment of muscle and nonmuscle disease.

Bone marrow transplantation for autosomal recessive osteopetrosis. A report from the Working Party on Inborn Errors of the European Bone Marrow Transplantation Group

The outcomes of 69 patients who received allogeneic bone marrow grafts for autosomal recessive osteopetrosis in the period between 1976 and 1994 were analyzed retrospectively. Four patients received bone marrow transplants (BMT) without prior myeloablative conditioning; transient osteoclast function was demonstrated in one of them. Sixty-five patients received myeloablative pretreatment. Recipients of a genotypically human leukocyte antigen (HLA)-identical BMT had an actuarial probability for 5-year survival, with osteoclast function, of 79%; recipients of a phenotypically HLA-identical bone marrow graft from a related or unrelated donor, or one HLA-mismatched graft from a related donor, had an actuarial probability for 5-year survival, with osteoclast function, of 38%; patients who received a graft from an HLA-haplotype mismatched related donor had a probability for 5-year survival of only 13%. The main problems in haplotype-nonidentical BMT were graft failure and BMT-related complications such as sepsis, bleeding, and interstitial pneumonia. Osteoclast function developed in all patients with full engraftment. Recovery of osteoclast function was associated with severe hypercalcemia in 24% of the patients with engraftment, especially those older than 2 years of age. At the time of BMT, severe visual impairment was present in 35% of the patients; of the 15 patients who had visual impairment at the time that a successful BMT was performed, two had improvement after BMT (13%). Within the total group, one patient had neurodegeneration. Engraftment of healthy donor cells had no influence on the progression of that abnormality and BMT thus had no beneficial effect on this phenotype of osteopetrosis. In general, however, early BMT remains the only curative treatment for autosomal recessive osteopetrosis.

The role of cellular and extracellular matrix adhesion proteins in organ transplantation

The specific adhesion of cells to other cells or to particular tissue microenvironments is a basic function of cell migration and recognition, and underlines many biologic processes including embryogenesis, repair and immunity. Leukocytes express an array of surface receptors broadly known as "accessory adhesion molecules." which mediate most cell-cell interactions, direct lymphocyte traffic between anatomical compartments, and facilitate cellular adhesion to the inflammation or alloantigenic sites (Springer 1990). In addition, adhesion molecules are involved in the process of antigen recognition, and may costimulate cell activation and transformation. These proteins are thought to affect the very early antigen independent events between host leukocytes and vascular endothelium. Because of these activities, the subject of adhesion molecules is gaining interest in the field of organ transplantation, in both conceptualization and development of novel therapeutic strategies (de Sousa et al. 1991, Kupiec-Weglinski et al. 1993a, Heemann et al. 1993).

Characterization of anti-canine cytokine monoclonal antibodies specific for IFN-gamma: effect of anti-IFN-gamma on renal transplant rejection

Two murine monoclonal antibodies specific for IFN-gamma, ADI-1, and ADI-23 (both IgG1 kappa), were generated in BALB/c mice. The ADI-1 exhibited a higher avidity for canine rIFN-gamma than for nIFN-gamma and human rIFN-gamma. In contrast, the ADI-23 showed equal avidity for the three IFN-gamma preparations. The anti-canine IFN-gamma mAb did not bind to mouse and rat rIFN-gamma. The ADI-1, and ADI-23 mAb were also tested for binding to human rTFN-alpha and, contrary to our expectations, it was found that ADI-23 showed significant binding to human rTFN-alpha and rIFN-gamma, in contrast to ADI-1. Both anti-canine IFN-gamma mAb stained 48-h PHA-induced dog lymphoblasts. A two-site mAb ELISA was developed, which was linear in the range of 7-500 ng of canine rIFN-gamma, which indicated that the two mAb detected non-overlapping epitopes on the canine rIFN-gamma molecule. We studied the effect of ADI-1 on the prolongation of canine renal allografts. Recipients of kidney allografts, that were treated with ADI-1 by continuous arterial infusion, were prolonged to 22 and 25 days, compared to 9 and 13 days for animals given the IgG1 isotype control.

[Immunologic aspects of bone marrow transplantation]

Allogeneic bone marrow transplantation is concerned by immunology by at least two aspects: the first one is the acceptance of the graft by the host and reciprocally and the second one is that it constitutes an unique human model of immune reconstitution. In this review of the immunological aspects, we deal with the selection of the bone marrow donor (related or not) especially on the base of HLA compatibility and the graft-versus-host disease (GVH) with the clinical manifestations, the usual treatments, the supposed cellular mechanisms and the risk factors of developing such complications. The graft versus leukemia effect (GVL) which may be linked to the GVH disease and the mechanisms of rejection and take of the graft are also reviewed as well as the immune reconstitution following the immune deficiency due to the conditioning treatment and the occurrence of a GVH disease.