Monoclonal anti-T Cell Research Articles

Biological Drugs in Guillain-Barré Syndrome: An Update.

Background: Guillain-Barré Syndrome (GBS) is currently considered the most common global cause of acute flaccid paralysis. Currently, standard therapy for Guillain-Barré Syndrome includes intravenous immunoglobulin or plasma exchange. Despite medical advances regarding these treatments, many treated patients do not reach full recovery. Therefore several biological agents have attracted the attentions from researchers during the last decades, and various studies have investigated their role in Guillain-Barré Syndrome.Objective:The present study aims to address emerging biological approaches to GBS while considering their efficiency and safety in treating the disease.Materials and Methods: An extensive electronic literature search was conducted by two researchers from April 2016 to July 2016. Original articles, clinical trials, systematic reviews (with or without meta-analysis) and case reports were selected. Titles and abstracts of papers were screened by reviewers to determine whether they met the eligibility criteria, and full texts of the selected articles were retrieved.Results: Herein authors focused on the literature data concerning emerging biological therapeutic agents, namely anti-C5 monoclonal antibody (Eculizumab), anti-C1q monoclonal antibody, anti-T cell monoclonal antibody, anti-CD2 monoclonal antibody, anti L-selectin monoclonal antibody, anti-CD20 monoclonal antibody (Rituximab), anti-CD52 monoclonal antibody (Alemtuzumab) and cytokine targets. By far, none of these agents have been approved for the treatment of GBS by FDA.Conclusion:Literature findings represented in current review herald promising results for using these biological targets. Current review represents a summary of what is already in regards and what progress is required to improve the immunotherapeutic approach of treating GBS via future studies.

CD3 Monoclonal Antibodies: A First Step Towards Operational Immune Tolerance in the Clinic

Type 1 diabetes (T1D) is a prototypic organ-specific autoimmune disease resulting from the selective destruction of insulin-secreting β-cells within the pancreatic islets of Langerhans. It is caused by an immune-mediated inflammation, involving autoreactive CD4⁺ and CD8⁺ T lymphocytes that infiltrate the islets and initiate insulitis. The use of exogenous insulin is the current standard treatment. However, in spite of significant advances, this therapy is still associated with major constraints, including risk of hypoglycemia and severe degenerative complications. As T1D mainly affects children and young adults, any candidate immune therapy must be safe, and it must avoid a sustained depression of immune responses with all its attendant problems of recurrent infection and drug toxicity. In this context, inducing or restoring immune tolerance to target autoantigens would be the ideal approach. We refer to immune tolerance here as the selective damping of the damaging autoimmune response following a short treatment, while keeping intact the capacity of the host to respond normally to exogenous antigens. The therapeutic approach we discuss in this article originates from attempts to induce tolerance both to soluble antigens and tissue antigens (i.e. alloantigens and autoantigens) by using biological agents that selectively interfere with lymphocyte activation, namely polyclonal and monoclonal anti-T cell antibodies. The challenged dogma was that, in an adult-primed immune system, it was not possible to restore self-tolerance therapeutically without the use of exogenous autoantigen administration. The reality has been that, in diabetes, endogenous host autoantigen can fulfill this role because a significant amount of functioning β-cells remains, even at the time of established hyperglycemia. Experimental results obtained in the 1990s showed that a short-term CD3 antibody treatment in recently diagnosed diabetic non-obese diabetic (NOD) mice induced permanent remission of the disease by restoring self-tolerance. Based on these findings, phase I, II, and III trials were conducted using two distinct humanized Fc-mutated antibodies to human CD3, namely ChAglyCD3 (otelixizumab) and OKT3γ1 Ala-Ala (teplizumab). Overall, when dosing was adequate, the results demonstrated that CD3 antibodies preserved β-cell function very efficiently, maintaining significantly high levels of endogenous insulin secretion in treated patients for up to 24 months after treatment. These data provided the first proof of concept for a long-term therapeutic effect in T1D following a short course administration of a therapeutic agent. Our aim is to review these data and to discuss them in the context of the pitfalls linked to pharmaceutical development, especially in the context of pediatric patients, as in autoimmune diabetes.

Antigen-dependent T lymphocytes (TcRβ +) are primarily differentiated in the thymus rather than in other lymphoid tissues in sea bass ( Dicentrarchus labrax, L.)

All jawed vertebrates share lymphocyte receptors that allow the recognition of pathogens and the discrimination between self and non-self antigens. The T cell transmembrane receptor (TcR) has a central role in the maturation and function of T lymphocytes in vertebrates via an important role in positive selection of the variable region of TcR αβ/γδ chains. In this study, the TcRβ transcript expression and TcRβ + cell distribution during the ontogeny of the immune system of sea bass ( Dicentrarchus labrax, L.) were analysed. RT-PCR analysis of larvae during early development demonstrated that the β chain transcript is expressed by 19 days post-fertilisation (p.f.). RNA probes specific for the β chain were synthesised and used for in situ hybridisation experiments on 30 day p.f. to 180 day old juvenile larvae. A parallel immunohistochemical study was performed using the anti-T cell monoclonal antibody DLT15 developed in our laboratory [Scapigliati et al., Fish Shellfish Immunol 1996; 6:383–401]. The first thymus anlage was detectable at 32–33 days p.f. (Corresponding to about 27 days post-hatch). DLT15 + cells were detected at day 35 p.f. in the thymus whereas TcRβ + cells were recognisable at day 38 p.f. in the thymus and at day 41 p.f. in the gut. TcRβ + cells were observed in capillaries from 41 to 80 days p.f. At day 46 p.f., TcRβ + cells were identified in the head kidney and were detected in the spleen 4 days later. The present results demonstrate that TcRβ + cells can be differentiated first in the thymus and then in other organs/tissues, suggesting potential TcRβ + cell colonisation from the thymus to the middle gut. Once the epithelial architecture of the thymus is completed with the formation of the cortical-medullary border (around 70–75 days p.f.), DLT15 + cells or TcRβ + cells are confined mainly to the cortex and cortical-medullary border. In particular, a large influx of TcRβ + cells was observed at the cortical-medullary border from 72 to 90 days p.f., suggesting a role in positive selection for this thymic region during the ontogeny of the fish immune system. This study provides novel information about the primary differentiation and distribution of TcRβ + cells in sea bass larvae and juveniles.

Local immunosuppressive therapy with monoclonal anti-T cell antibody on renal allograft survival in the rat.

Considerable interest in the experimental and clinical use of MoAbs as potential therapeutic agents in allograft rejection has been generated by the recent reports of striking prolongation. In this study we investigated the efficacy of the local administration of MoAb OX-19 which is directed to the rat CD5 equivalent, through the renal artery using a rat kidney transplant model, in order to develop a potent method for modifying rejection while minimizing the systemic side effects. Untreated Lewis rats (LEW, RT-1(1)) rejected Brown-Norway rat (BN, RT-1n) kidney at 7.8 +/- 0.2 days (n = 10). Mean survival time (MST) of recipients treated with OX-19 (75 micrograms/kg per day) as single bolus injections via the dorsal penile vein for 7 days was 7.0 +/- 0.2 days (n = 5, NS). LEW hosts receiving OX-19 (75 micrograms/kg per day) continuously for 7 days via a femoral vein by using an osmotic minipump (IV-treated group) showed a slight prolongation of graft survival (MST = 8.8 +/- 0.9 days, n = 5), but this was not statistically significant. On the other hand, local continuous intrarenal arterial infusion of OX-19 (75 micrograms/kg per day) for 7 days (RA-treated group) significantly prolonged the graft survivals (MST = 16.8 +/- 1.3 days, n = 8, P < 0.01). Histological examination of MoAb-treated LEW hosts on day 6 post-grafting revealed that kidney grafts from RA-treated hosts showed a slight tubular necrosis, but reduced mononuclear cell infiltration, whereas kidney grafts from IV-treated hosts displayed a severe mononuclear cell infiltration around the artery with interstitial oedema. Moreover, the local intrarenal administration of OX-19, even when the dose is delayed until day 4 after renal grafting, has a therapeutic effect for on-going acute allograft rejection (MST = 11.4 +/- 0.8 days, n = 8) compared with administration of OX-19 intravenously from day 4 after grafting (MST = 7.6 +/- 0.2 days, n = 5, P < 0.01) or with no treatment (MST = 7.8 +/- 0.2 days, P < 0.01). The phenotype of graft infiltrating cells (GIC) was investigated on day 6 post-grafting. There was a significantly lower percentage of cells positive for OX-19, OX-8, OX-26 (transferrin receptor), and OX-39 (IL-2 receptor) in the RA group than in the IV group.(ABSTRACT TRUNCATED AT 400 WORDS)

Heart allograft acceptance induced by anti-CD3 antibody in high-responder rats: Effect on foxp3 and cytokine expression and graft infiltration

The ability of anti-T cell monoclonal antibody G4.18 and polyclonal anti-lymphocyte serum (ALS) to induce long-term graft survival was examined in a high-responder rat heart transplant model. Heterotopic heart allografts were performed from PVG rat strain donors to high-responder Lewis recipients. Immunosuppressive properties of G4.18 and ALS were investigated by immunohistochemistry and PCR analysis. Untreated graft rejection was 8.5 days while treatment with 1 ml ALS prolonged survival to 11.5 days ( p = 0.01). Treatment with 7 mg/kg G4.18 on days 1 and 3 prolonged survival to > 100 days ( p = 0.002 vs. control and p = 0.002 vs. ALS) but did not induce tolerance. Acceptance was associated with marked inhibition of cellular infiltration and inflammatory cytokine expression and only a brief, slight increase in Foxp3:T cell ratio in the graft and no increase in the spleen. In conclusion, G4.18 treatment led to long-term heart transplant survival associated with marked inhibition of early inflammation. Failure to develop tolerance was associated with a lack of early accumulation of Foxp3 cells in the graft or spleen.

Update on Therapeutic Monoclonal Antibodies

Monoclonal antibodies are among the most important class of drugs introduced into the therapeutic armamentarium since the introduction of antimicrobials in the 1930s. The first therapeutic monoclonal antibody, the anti T-cell monoclonal antibody OKT4, was licensed in 1986. Since then, 18 additional antibodies have been licensed in the US, with many more in the pipeline. Before 1986, many monoclonal antibodies were available for laboratory studies, notably to identify specific cells in the blood and tissues. This is best illustrated by the cluster designation (CD) system for antigens present on hematopoietic cells, now numbering over 200.

Induction of immunological tolerance using monoclonal antibodies: Applications to organ transplantation and autoimmune disease

Immunologic tolerance is a state of immune paralysis specific to a given antigen (the tolerogen) coexisting with the maintenance of normal immunocompetence towards other antigens. Anti-T cell monoclonal antibodies allow its induction in organ transplantation and autoimmune disease essentially through the stimulation of regulatory T cells. Very promising results obtained in animals have been recently confirmed in the human in recent-onset insulin-dependent diabetes mellitus with an anti-CD3 antibody (with long-term remission of the disease following a treatment of only six days). To cite this article: J.-F. Bach, C. R. Biologies 329 (2006).

Long-Term Trends in Allograft Survival

Kidney transplantation has changed dramatically over the past decade. Many advances have occurred that result in shorter hospital stays, decreased acute rejection, less infectious morbidity, and improved long-term allograft survival. Many factors are responsible for the improvement in kidney transplantation, and these factors are discussed in this review. These successes have led to a paradox in the care of the kidney-transplant recipient, however. As the short-term complications are prevented or successfully managed, more patients will develop chronic problems with the function of the allograft.

Prolonged survival of fetal pig islet xenografts in mice lacking the capacity for an indirect response.

Xenografts of islets from organ-cultured fetal pig pancreases transplanted into non-immunosuppressed mice are rejected within 10 days. Immunosuppression with anti-T cell (anti-CD4) monoclonal antibody alone delays rejection of these xenografts for about 28 days, but rejection eventually occurs despite marked depletion of T cells. To determine if the critical CD4+ T cells responsible for xenograft islet rejection function through the direct or indirect pathway, selective class II-deficient mice that express class II antigens only on their thymic epithelium (not on peripheral cells) with normal numbers of CD4+ T cells, (class II-, CD4+), were used as recipients of xenograft islets to test if rejection occurs in the absence of an indirect response. Control (C57BL/6) or class II-, CD4+ mice were transplanted under the kidney capsule with cultured fetal pig islets. Class II-, CD4+ mice have normal numbers of B cells, CD4+, gamma delta T cells, and slightly increased numbers of CD8+ T cells. Additional mice were thymectomized before receiving anti-CD4 or anti-CD8 monoclonal antibodies. Islet graft survival was determined histologically as fetal pig islets were too immature to secrete insulin. Xenograft survival in control animals was 7 to 14 days. In contrast, graft survival in class II-, CD4+ mice was significantly prolonged to greater than 35 days. Depletion of CD8+ T cells in class II-, CD4+ mice prolonged graft survival to about 70 days. Depletion of CD4+ T cells from these mice further prolonged xenograft survival to about 100 days. These results suggest that the rejection of pig islets by mice initially depends on a CD4 dependent indirect response. The CD4 direct response also contributes to graft destruction. CD8+ T cells also participate in graft destruction, albeit weakly.

Non-ischemic left ventricular dysfunction after pediatric cardiac transplantation: treatment with plasmapheresis and OKT3

Background Acquired left ventricular dysfunction after pediatric cardiac transplantation is associated with a high mortality rate. It often occurs without biopsy evidence of cellular rejection or severe transplant coronary arteriopathy. Methods We employed a protocol for treatment of acquired, non-ischemic left ventricular dysfunction utilizing plasmapheresis, monoclonal anti–T-cell antibody (OKT3), cyclophosphamide and steroids, regardless of the results of endomyocardial biopsy. Left ventricular dysfunction was defined as an echocardiographic shortening fraction of <29% and/or symptoms of congestive heart failure requiring inotropic support. Transplant coronary arteriopathy was excluded by coronary angiography in all cases. Results Ten pediatric heart transplant recipients were treated for 13 episodes of non-ischemic left ventricular dysfunction. Biopsy scores were low grade (ISHLT Grade 1A or 1B) in 8 episodes. Eight of 10 patients had a history of non-compliance in regularly taking immunosuppressant medications. Inotropic support was required in 9 of 13 cases, with a median duration of 5 days. Median left ventricular shortening fraction was 17% at time of presentation. Normalization of shortening fraction occurred a median of 40 days from the start of treatment. Survival to hospital discharge occurred in 11 of 13 (85%) patients. Long-term patient survival, however, was only 50% at 24 months after presentation with a first episode of acquired left ventricular dysfunction. Conclusions Use of plasmapheresis, OKT3, cyclophosphamide and steroids resulted in successful short-term reversal of non-ischemic left ventricular dysfunction in pediatric heart transplant patients, but long-term survival remained poor.

Positive T lymphocytotoxic cross-match in living donor liver transplantation

The influence of lymphocytotoxic cross-match on survival or acute rejection in living donor liver transplantation (LDLT) has not been well examined. We analyzed 133 consecutive adult LDLT cases and assessed patient survival and acute rejection rates. Patients with a positive T lymphocytotoxic cross-match (n = 12) had a significantly higher chance of rejection within 6 weeks of LDLT (67% versus 28%, P < .001). All of the rejection episodes were successfully treated with bolus methylprednisolone therapy or anti-T cell monoclonal antibody. T lymphocytotoxic cross-match-positive grafts had no influence on patient survival (79% versus 90% at 3 years, P = .91). The results show that a positive cross-match graft should not be considered a contraindication for LDLT. (Liver Transpl 2003;9:1062-1066.)

Antitumor effect of donor marrow graft rejection induced by recipient leukocyte infusions in mixed chimeras prepared with nonmyeloablative conditioning: critical role for recipient-derived IFN-γ

AbstractSome patients lose chimerism following nonmyeloablative hematopoietic cell transplantation (HCT), yet, surprisingly, enjoy sustained tumor remissions. We hypothesized that host-versus-graft (HVG) alloresponses might induce antitumor effects against recipient tumors. We explored this question in mice by administering recipient leukocyte infusions (RLIs) to mixed chimeras established with nonmyeloablative conditioning. Mixed chimeras were prepared in the B10.A (H2a)→B6 (H2b) strain combination using depleting anti–T-cell monoclonal antibodies (mAbs), cyclophosphamide, and thymic irradiation. B6 myeloid leukemia cells (MMB3.19) were administered 7 days following donor lymphocyte infusion (DLI) or RLI on day 35. Conversion to full donor chimerism occurred without graft-versus-hostdisease (GVHD) following DLI, whereas RLI led to loss of chimerism. Both RLI and DLI significantly delayed tumor mortality. In another strain combination (B10.BR [H2k]→BALB/c [H2d]), RLI-induced or spontaneous loss of chimerism was associated with antitumor effects against the host-type B-cell lymphoma A20. HCT was essential for the antitumor effect of RLI. RLI induced elevated serum interferon-γ (IFN-γ) levels, and recipient-derived IFN-γ was critical for their antitumor effects. Thus, HVG reactions (spontaneous or induced by RLI) mediate antitumor effects against hematologic malignancies via a recipient-derived IFN-γ–mediated mechanism. A novel approach to achieving anti-tumor effects without the risk of GVHD is suggested.

Tolerance induction in clinical transplantation: the pending questions.

Despite the dramatic improvement of early graft survival due to the introduction of cyclosporin, late graft loss caused by chronic rejection and the lethal consequences of long-term immunosuppression, such as infection and cancer, remain major concerns for the transplantation community. Tolerance induction would avoid these complications. The ways to go are controversial, reflecting the redundancy of rejection pathways. They include the induction of central tolerance by establishment of mixed chimerism through hematopoietic stem cell transplantation and the induction of "operational tolerance" through immunodeviation involving dendritic or regulatory T cells. Major advances have been made in animal models exploring these strategies and, some preliminary data are even now available in humans, allowing the initiation of pilot clinical trials. In this article, we discuss the key questions that these trials will have to address.

Lymphohematopoietic graft-vs.-host reactions can be induced without graft-vs.-host disease in murine mixed chimeras established with a cyclophosphamide-based nonmyeloablative conditioning regimen.

Mixed hematopoietic chimerism can be induced in mice receiving allogeneic bone marrow transplantation (BMT) after nonmyeloablative host conditioning with depletion T cells with of anti-T cell monoclonal antibodies (mAbs), low-dose (3 Gy) total-body irradiation (TBI), and local thymic irradiation (7 Gy). These mice are specifically tolerant to donor and host antigens. When nontolerant donor T cells are given to chimeras several months after BMT, full donor-type chimerism develops, but graft-vs.-host disease (GVHD) does not occur. The induction of such lymphohematopoietic GVH reactions without GVHD could provide an approach to separating graft-vs.-leukemia (GVL) from GVHD in patients with hematologic malignancies. To make the nonmyeloablative conditioning regimen described above more cytoreductive for such malignancies, we have now modified it by replacing TBI with cyclophosphamide (CP). Treatment with anti-CD4 and anti-CD8 mAbs on day -5, 200 mg/kg CP on day -1, and 7 Gy thymic irradiation on day 0 was only slightly myelosuppressive and allowed fully major histocompatibility complex (MHC)-mismatched (with or without multiple minor antigen disparities) allogeneic bone marrow to engraft and establish long-term mixed chimerism in 40 to 82% of recipients in three different strain combinations. The administration of nontolerant donor spleen cells at 5 weeks or at 5, 8, and 11 weeks posttransplant was capable of eliminating host hematopoietic cells, leading to full or nearly full donor chimerism in six of six and two of four chimeric animals in two different strain combinations. No clinical evidence of GVHD was observed in any recipients of these donor leukocyte infusions (DLI). These studies demonstrate that induction of mixed chimerism with nonmyeloablative conditioning followed at appropriate times by DLI might allow lymphohematopoietic GVH reactions, and hence GVL effects, to eliminate chronic hematologic malignancies without causing clinically significant GVHD.

Cyclophosphamide, but not CTLA4Ig, prolongs survival of fetal pig islet grafts in anti-T cell monoclonal antibody-treated NOD mice.

Fetal pig islets, xenografted after organ culture into non-immunosuppressed prediabetic NOD mice, are rejected within 10 days. Immunosuppression with anti-T cell (anti-CD4 and anti-CD3) monoclonal antibodies alone is highly effective in delaying graft rejection in this discordant model, but rejection eventually occurs, usually within 80 days, despite marked depletion of T cells. In an attempt to prevent rejection, we used cyclophosphamide (CP), a powerful anti-B cell agent, or CTLA4Ig, an inhibitor of T-cell co-stimulation [via B7-1 (CD80) and B7-2 (CD86)], either given in combination with anti-CD4 (GK1.5) or anti-CD3 (KT3) MAb to the recipient mice. The addition of cyclophosphamide in a dose that significantly depleted B cells in peripheral blood was highly effective in preventing rejection, with xenografts surviving for at least 112 days, when the experiment was terminated. CTLA4Ig, administered alone, did not prevent delayed rejection (rejection occurred in <60 days) and, in contrast to CP, did not prevent delayed rejection when used in combination with GK1.5 and KT3 treatment. Thus, immunosuppressive agents found to be highly effective in other strains, e.g., CTLA4Ig and anti-T cell MAbs, had a lesser effect in NOD mice but the addition of an anti-B cell drug, CP, was useful. This finding may be applicable to patients with IDDM.

Rheumatoid Arthritis--heresies and speculations.

RHEUMATOID ARTHRITIS—HERESIES AND SPECUIATIONS DAVID A. FOX" Introduction Since rheumatoid arthritis (RA) gradually became defined as a distinct clinical entity early in the 20th century, intensive and prolonged efforts to understand its cause have met largely with frustration. Concurrently, improvement in the treatment of RA has occurred slowly and has made only a modest impact on the natural history of this condition. In the course of RA, polyarticular inflammation is generally followed by destruction of cartilage, bone, and other structures of the joint, with consequent deformity and disability. The dogma that joint damage is the consequence of inflammation, rather than a parallel process, has been called into question by discrepancies between the anti-inflammatory potencies ofvarious therapeutic maneuvers and their generally unimpressive effects on erosion of cartilage and bone. Ultimately, RA is certainly capable of being a fatal condition , and on average, the mortality of individuals with this condition is approximately doubled, once adjustments for age and other comorbid conditions have been made. In this essay, I will present a series of "heresies" and speculations designed to challenge current concepts of the pathogenesis of RA. I will attempt to focus on issues for which current dogma leads to predictions that are difficult to verify, or seems to be hampering our understanding of RA rather than yielding clear insights. Heresy #1: RA Does Not Have a Cause It seems reasonable that clues to proper treatment of RA will come from delineation ofits cause. Figure 1 shows four hypotheses or paradigms within This work was supported in part by NIH grant AR-38477. The author wishes to thank Gigi Rowe for preparation of the manuscript. *Rackhara Arthritis Research Unit, Division of Rheumatology, Specialized Center of Research in Rheumatoid Arthritis, and The University of Michigan Multipurpose Arthritis and Musculoskeletal Diseases Center, Ann Arbor, MI 48109.© 1997 by The University of Chicago. AU rights reserved. 0031-5982/97/4002-1001$01.00 Perspectives in Biology and Medicine, 40, 4 ¦ Summer 1997 | 479 Synoviocyte transformation, synoviocyte interaction with macrophages, cartilage, and bone Cellular immune mechanisms (T cells, cytokines, monocytes) Humoral immune mechanisms (RF, immune complexes,---------complement ) Infection_______________________^. 19201940196019802000 Fig. 1.—Hypotheses for the cause of RA. which the cause of RA has been sought for most of this century. Once RA was defined as a distinct entity, early concepts of its etiology centered on infectious agents. However, with the discovery of rheumatoid factor and subsequent understanding of antibodies at a protein and genetic level, humoral immune mechanisms took center stage in studies of the pathogenesis and even the etiology of RA. It was believed at that time that an autoimmune response mediated by antibodies could cause RA, as well as a variety of other autoimmune diseases. In the 1980s, the development of monoclonal antibodies led to rapid growth in understanding of T cell development , T cell activation, and T lymphocyte surface structures, and immunogenetic studies established the association of various rheumatic diseases, including RA, with specific major histocompatibility complex (MHC) polymorphisms . In this setting cellular immune responses driven by T lymphocytes became the focus ofattention in the pathogenesis ofRA, as the disease was redefined as a T cell-driven autoimmune condition [I]. Within the past few years, however, the role of the T cell has come into question, in view of the presence of only modest amounts of T cell cytokines in the synovial compartment and disappointing results in therapeutic trials of anti-T cell monoclonal antibodies [2]. The apparently autonomous destructive potential of synoviocytes in chronic RA has intensified focus on the transformation of such cells and unusual cell-cell interactions within the joint as central to the etiology and pathogenesis of this disease. Each new paradigm for looking at RA has been too simple at its inception and has been accompanied by excessive enthusiasm. Therefore, when limitations of the paradigm have been encountered, scientific opinion has shifted abruptly to a new model, unfortunately forgetting valuable clues gained by exploration of the previous model. In trying to identify the cause of RA, a reasonable question would be whether the correct technology exists to address this question. One might argue that until recently this may not have been the case. But given the imposing...

Superiority of polyclonal ATG (P-ATG) over monoclonal anti-T cell antibodies (M-ATA) in immunosuppression (IS) for islet allografting

The present study investigates the pharmacological activity of the nitric oxide (NO) donor S-nitrosoglutathione (GSNO) on the plasma glucose and insulin levels in healthy normoglycemic dogs. The plasma nitrate and nitrite concentrations were measured by a commercial autoanalyzer and taken as the biochemical markers of in vivo nitric oxide formation. Plasma glucose levels were measured by the glucose oxidase method, while the insulin levels were determined by radioimmunoassay. The possible effect of the coadministration of ascorbic acid (vitamin C) and GSNO on plasma glucose levels was also examined. In healthy normoglycemic dogs, administration of 35 and 50 mg/kg of GSNO caused a dose-dependent increase in postprandial plasma glucose levels. The plasma glucose levels were significantly elevated at the 1.5-, 2.0-, and 2.5-h time intervals of the oral glucose tolerance test at both concentrations of GSNO (P < 0.05). These values were significantly higher than those obtained using captopril (control). Furthermore, coadministration of 35 mg/kg of GSNO and 50 mg/kg ascorbic acid enhanced the postprandial hyperglycaemic effect observed for the administration of only 35 mg/kg of GSNO. There was a 35–100% increase in plasma nitrate concentration on administration of both doses of GSNO. Intravenous administration of GSNO (35 mg/kg) and captopril (20 mg/kg) significantly decreased the mean arterial blood pressure and increased the heart rate. The blood pressure-lowering effect of these drugs was more pronounced on systolic than on diastolic blood pressure (P < 0.05). These results suggests that in healthy normoglycaemic dogs: (a) nitric oxide released from GSNO increases postprandial plasma glucose levels and inhibits glucose-stimulated insulin secretion, (b) ascorbic acid enhances the postprandial hyperglycaemic effect of GSNO, probably by increasing the release of NO, and (c) GSNO decreases mean arterial blood pressure and increase heart rate in normotensive dogs.

Indefinite allograft survival induced by the combination of multiple donor-specific transfusions, cyclosporine, and anti-T cell monoclonal antibody in a protocol relevant to cadaveric organ transplantation: The importance of prolonged posttransplant cyclosporine coverage

Indefinite allograft survival induced by the combination of multiple donor-specific transfusions, cyclosporine, and anti-T cell monoclonal antibody in a protocol relevant to cadaveric organ transplantation: The importance of prolonged posttransplant cyclosporine coverage

Immunosuppression by Fc region‐mismatched anti‐T cell antibody treatment

Formation of anti-antibodies (anti-Ab) is known to counteract immunotherapy with anti-T cell antibodies. Our previously described immunological approach prevented anti-Ab with the consequence of prolonged survival of fully mismatched skin grafts in C57BL/6 mice. These mice were treated with a single priming injection of a monoclonal anti-T cell Ab followed by repeated injections of anti-T cell mAb differing in species origin from the priming mAb. We now show prolonged tolerance to discordant xenogeneic, to bispecific, and even to polyclonal Ab, and demonstrate that the underlying immunosuppressive principle is due to a difference in heavy chain constant region between first and second antibodies, independent of whether or not they share the same idiotype. To examine this phenomenon, a panel of mAb was generated which share the same mouse anti-Thy-1.2 idiotype, but carry a human IgG1(T23), IgG3(T212C8), or mouse IgG2a(MmT1) constant heavy chain region. We found that sequential injection of MmT1 and T23 according to the above treatment schedule induced huIgG1 isotype-specific tolerance to T23, which was similar to that seen when using a primary mAb (MmT5) that was, instead, fully mismatched with T23 in both idiotype and constant region. Thus, differences of idiotype between primary and booster Ab were inconsequential for their ability to inhibit anti-Ab formation. This novel form of induced specific tolerance to anti-T cell Ig survived graft rejection and was still evident 230 days after termination of the T cell depletion protocol. Taken together, these results demonstrate that rechallenge with Fc region-mismatched Ab opens an immunological window that allows for induction of tolerance to immunogenic anti-T cell Ab and prolonged immunosuppression.

Comparison of antibody specificities of four anti-thymocyte/anti-lymphocyte globulin products

The antibody specificities of four anti-thymocyte/anti-lymphocyte globulin (ATG/ALG) products were examined by using a competitive immunofluorescence assay as a first step in clarifying the mechanism of ATG/ALG action. Lymphoglobuline and thymoglobuline had similar specificities with the exception of reactivity to CD28 antigen. These two ATG products blocked anti—T-cell antibodies and anti—LFA-1α antibody, while they did not react with natural killer—cell and stem-cell antigens. Antibody specificity of ATG-Fresenius was also similar to that of lymphoglobuline and thymoglobuline, except that it did not contain anti-CD4 antibody. Ahlbulin did not inhibit the binding of anti—T-cell monoclonal antibodies. Analysis of antibody specificities contained in ATG/ALG products is necessary to define specificity or combinations of specificities that are responsible for the clinical effectiveness of ATG/ALG.