The immunosuppressant 15-deoxyspergualin [correction of 1,5-deoxyspergualin] reveals commonality between preT and preB cell differentiation

Novel Complement C5 Small-interfering RNA Lipid Nanoparticle Prolongs Graft Survival in a Hypersensitized Rat Kidney Transplant Model

BACKGROUND

Prophylaxis of antibody-mediated rejection (AMR) caused by donor-specific antibodies remains challenging. Given the critical roles of complement activity in antibody-mediated graft injury, we developed a lipid nanoparticle (LNP) formulation of small-interfering RNA against complement C5 (C5 siRNA-LNP) and investigated whether C5 siRNA-LNP could downregulate the complement activity and act as an effective treatment for AMR.

METHODS

Lewis recipient rats were sensitized by skin grafting from Brown Norway donor rats. Kidney transplantation was performed at 4 wk post-skin grafting.C5 siRNA- or control siRNA-LNP was administered intravenously, and the weekly injections were continued until the study's conclusion. Cyclosporin (CsA) and/or deoxyspergualin (DSG) were used as adjunctive immunosuppressants. Complement activity was evaluated using hemolysis assays. The deposition of C5b9 in the grafts was evaluated using immunohistochemical analysis on day 7 posttransplantation.

RESULTS

C5 siRNA-LNP completely suppressed C5 expression and complement activity (hemolytic activity ≤ 20%) 7 d postadministration. C5 siRNA-LNP in combination with CsA and DSG (median survival time: 56.0 d) prolonged graft survival compared with control siRNA-LNP in combination with CsA and DSG (median survival time: 21.0 d; P = 0.0012; log-rank test). Immunohistochemical analysis of the grafts revealed that downregulation of C5 expression was associated with a reduction in C5b9-positive area ( P = 0.0141, Steel-Dwass test).

CONCLUSIONS

C5 siRNA-LNP combined with immunosuppressants CsA and DSG downregulated C5 activity and significantly prolonged graft survival compared with control siRNA-LNP with CsA and DSG. Downregulation of C5 expression using C5 siRNA-LNP may be an effective therapeutic approach for AMR.

A small molecule inhibitor for ATPase activity of Hsp70 and Hsc70 enhances the immune response to protein antigens

The ATPase activities of Hsp70 and Hsc70 are known to be responsible for regulation of various biological processes. However, little is known about the roles of Hsp70 and Hsc70 in modulation of immune responses to antigens. In the present study, we investigated the effect of apoptozole (Az), a small molecule inhibitor of Hsp70 and Hsc70, on immune responses to protein antigens. The results show that mice administered with both protein antigen and Az produce more antibodies than those treated with antigen alone, showing that Az enhances immune responses to administered antigens. Treatment of mice with Az elicits production of antibodies with a high IgG2c/IgG1 ratio and stimulates the release of Th1 and Th2-type cytokines, suggesting that Az activates the Th1 and Th2 immune responses. The observations made in the present study suggest that inhibition of Hsp70 and Hsc70 activities could be a novel strategy designing small molecule-based adjuvants in protein vaccines.

Is there B cell involvement in a rat model of spontaneous idiopathic nephrotic syndrome treated with LF15-0195?

BACKGROUND

The Buffalo/Mna (Buff/Mna) rat spontaneously develops idiopathic nephrotic syndrome (INS), and its nephropathy recurs after the renal transplantation of a healthy graft. Only LF15-0195 is able to cause regression of the Buff/Mna nephropathy and to induce regulatory T cells, which decrease proteinuria when transferred into proteinuric Buff/Mna rats. Based on previous research on B cells in human INS, we evaluated the involvement of B cells in our model and the impact of LF15-0195.

METHODS

We studied the effect of LF15-0195 on peripheral B cells by flow cytometry and quantitative reverse transcription-polymerase chain reaction. B cells were purified from LF15-0195-treated Buff/Mna rats in remission, and transferred into proteinuric Buff/Mna rats. We treated the Buff/Mna rats with mitoxantrone and measured the depletion of B/T cells in parallel with proteinuria.

RESULTS

LF15-0195 changed the phenotype of B cells: the number of naïve mature B cells increased significantly, while the number of switched, transitional 1, and transitional 2 B cells decreased. There were no changes in the amount of memory, activated or regulatory B cells. We observed a significant increase of immunoglobulin (Ig)M mRNA transcripts in the LF15-0195-treated Buff/Mna B cells compared to controls, but no difference in the level of IgG. This profile is consistent with a block in B cell maturation at the IgM to IgG switch. The transfer of B cells from LF15-0195-treated rats into proteinuric Buff/Mna rats did not have an effect on proteinuria. Mitoxantrone, despite causing a significant depletion of B cells, did not reduce proteinuria.

CONCLUSION

Despite LF15-0195 acting on B cells, the beneficial effects of this drug on nephrotic syndrome did not involve the induction of regulatory B cells. Moreover, the B cell depletion was not effective in reducing proteinuria, indicating that B cells are not a therapeutic target.

Regulatory T cells are critical to tolerance induction in presensitized mouse transplant recipients through targeting memory T cells

Memory T cells are a significant barrier to induction of transplant tolerance. However, reliable means to target alloreactive memory T cells have remained elusive. In this study, presensitization of BALB/c mice with C57BL/6 skin grafts generated a large number of OX40(+)CD44(hi)effector/memory T cells and resulted in rapid rejection of donor heart allografts. Recognizing that anti-OX40L monoclonal antibody (mAb) (alpha-OX40L) monotherapy prolonged graft survival through inhibition and apoptosis of memory T cells in presensitized recipients, alpha-OX40L was added to the combined treatment protocol of LF15-0195 (LF) and anti-CD45RB (alpha-CD45RB) mAb-a protocol that induced heart allograft tolerance in non-presensitized recipients but failed to induce tolerance in presensitized recipients. Interestingly, this triple therapy restored donor-specific heart allograft tolerance in our presensitized model that was associated with induction of tolerogenic dendritic cells and CD4(+)CD25(+)Foxp3(+) T regulatory cells (Tregs). Of note, CD25(+) T cell depletion in triple therapy recipients prevented establishment of allograft tolerance. In addition, adoptive transfer of donor-primed effector/memory T cells into tolerant recipients markedly reduced levels of Tregs and broke tolerance. Our findings indicated that targeting memory T cells, by blocking OX40 costimulation in presensitized recipients was very important to expansion of Tregs, which proved critical to development of tolerance.

C5 blockade with conventional immunosuppression induces long-term graft survival in presensitized recipients

We explored whether a functionally blocking anti-C5 monoclonal antibody (mAb) combined with T- and B-cell immunosuppression can successfully prevent antibody-mediated (AMR) and cell-mediated rejection (CMR) in presensitized murine recipients of life-supporting kidney allografts. To mimic the urgent clinical features of AMR experienced by presensitized patients, we designed a murine model in which BALB/c recipients were presensitized with fully MHC-mismatched C3H donor skin grafts one week prior to C3H kidney transplantation. Presensitized recipients demonstrated high levels of circulating and intragraft antidonor antibodies and terminal complement activity, rejecting grafts within 8.5 +/- 1.3 days. Graft rejection was predominantly by AMR, characterized by interstitial hemorrhage, edema and glomerular/tubular necrosis, but also demonstrated moderate cellular infiltration, suggesting CMR involvement. Subtherapeutic treatment with cyclosporine (CsA) and LF15-0195 (LF) did not significantly delay rejection. Significantly, however, the addition of anti-C5 mAb to this CsA/LF regimen prevented terminal complement activity and inhibited both AMR and CMR, enabling indefinite (>100 days) kidney graft survival despite the persistence of antidonor antibodies. Long-term surviving kidney grafts expressed the protective proteins Bcl-x(S/L) and A-20 and demonstrated normal histology, suggestive of graft accommodation or tolerance. Thus, C5 blockade combined with routine immunosuppression offers a promising approach to prevent graft loss in presensitized patients.

15-deoxyspergualin prevents mucosal injury by inhibiting production of TNF-α and down-regulating expression of MD-1 in a murine model of TNBS-induced colitis

The immunosuppressive drug 15-deoxyspergualin (DSG) is currently being used in clinical trials to prolong graft survival and reverse graft rejection. Here we evaluated whether DSG has a potential for ameliorating diseases characterized by mucosal inflammation. Using a murine model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, we were able to demonstrate that DSG reduced the severity of colitis. Therefore, colitic mice pretreated with DSG showed a striking improvement of the wasting disease compared with colitic mice, as assessed by weight loss as well as clinical, macroscopic and microscopic analysis. Also, we observed the significant change occurred in the CD19(+) B cell subset, which was decreased 15% in DSG pretreated colitic mice compared with colitic mice. However, DSG pretreatment does not influence the apoptotic population of T and B cells. Compared with colitic mice, down-regulation of TNF-alpha production was observed in DSG pretreated colitic mice. In addition, DSG pretreated colitic mice significantly reduced expression of MD-1 compared with colitic mice on B cells and dendritic cells (DCs). Therefore, pretreatment with DSG resulted in a significant histologic improvement, protecting against mucosal ulcerations and reduced inflammatory response by modulating expression of MD-1, which plays a very important role in immune response on B cells and DCs. Also, this improvement was paralleled by a reduction in TNF-alpha levels. Collectively, current results demonstrate that DSG may be an effective agent for the treatment of diseases characterized by mucosal inflammation.

Therapeutics of Wegener's granulomatosis

The treatment of Wegener's granulomatosis, one of the most common forms of systemic vasculitis, has changed substantially over the past two decades. The principal aims of therapy are to control the disease swiftly, to limit the extent and severity of permanent organ damage, and to minimize the short-term and long-term morbidities that often result from therapy. This review provides an overview of the treatment regimens that are currently available for inducing and maintaining remission in patients with Wegener's granulomatosis, and also discusses newer agents that might have a role in the management of this disease in the future. Severe toxicity associated with the available agents and, therefore, there is keen interest in the development of alternative treatment strategies for this disease.

15-Deoxyspergualin and cyclophosphamide, but not mycophenolate mofetil, prolong survival and attenuate renal disease in a murine model of ANCA-associated crescentic nephritis

BACKGROUND

Here we compare the efficacy of cyclophosphamide (CYC) for treatment of crescentic nephritis (CGN) with the newer immunosuppressants 15-deoxyspergualin (DSG) and mycophenolate mofetil (MMF) in SCG/Kj mice, an inbred mouse strain that spontaneously develops CGN, systemic necrotizing vasculitis and antineutrophil cytoplasmic antibodies (ANCAs).

METHODS

Mice were randomly assigned to intraperitoneal treatment with either DSG (2 mg/kg/day), CYC (50 mg/kg/week), MMF (60 or 100 mg/kg/day) or vehicle (VEH, dextrose 5% 0.3 ml/day) beginning at the 10th week of life. ANCA, blood urea nitrogen (BUN) and proteinuria were determined in all animals regularly, and survival was calculated. Renal histology was obtained in the 18th week of life in the MMF- or VEH-treated groups and in the 24th week in DSG- or CYC-treated animals.

RESULTS

Mean survival in VEH-treated animals was 123 days. At that point, survival was 100% in the CYC- or DSG-treated animals (P<0.001). Survival in the MMF group (pooled data) was not significantly different from the VEH-treated animals [MMF, 117 days (95% CI 108-127)]. BUN (18th week, CYC 43+/-9 mg/dl and DSG 36+/-6 mg/dl vs VEH 73+/-28 mg/dl, P<0.001, MMF 66+/-26 mg/dl), 24 h proteinuria (18th week, CYC 0.4+/-0.2 mg and DSG 0.7+/-0.6 mg vs VEH 2.7+/-3 mg, P<0.001, MMF 2.2+/-3 mg) crescent formation (18th week, VEH 42+/-9%, MMF 39+/-11%; CYC 5+/-2% and DSG 22+/-7% vs VEH, P<0.05), glomerular immune complex deposition, and ANCA formation were significantly improved in CYC- and DSG- but not in MMF-treated animals when compared with controls.

CONCLUSION

DSG and CYC, but not MMF, prolong life, limit renal damage and prevent autoantibody formation in SCG/Kj mice.

Prolonged treatment of refractory Wegener's granulomatosis with 15-deoxyspergualin: an open study in seven patients

BACKGROUND

A subset of patients with Wegener's granulomatosis does not respond to daily oral cyclophosphamide (CYC) plus corticosteroids or suffers from intolerable side effects. A 6 month course of the immunosuppressant 15-deoxyspergualin (DSG) has previously been employed successfully in these refractory cases. However, there are no reports on long-term treatment with DSG.

METHODS

To document the effects of prolonged DSG treatment, this study reports on seven patients suffering refractory Wegener's granulomatosis, who were successfully treated with DSG over an average of 26.5 months (range: 11-55.5 months).

RESULTS

Before administration of DSG, patients had experienced an average of 6.6 relapses (range: 3-12) under an average of 5.4 (range: 2-11) different therapeutic approaches, which included CYC in all cases. All suffered active disease when DSG was initiated. Four were unresponsive to CYC and three did not tolerate it. DSG (0.5 mg/kg/day subcutaneous) was given for 2-3 weeks until the leukocyte count dropped to 3000/microl, followed by a rest until a leukocyte count of 4000/microl was reached again. No other immunosuppressants besides corticosteroids were given. All patients showed a long-lasting, favourable response to DSG with complete (n = 5) or partial (n = 2) remission. Only one case relapsed while being treated with DSG. Termination/interruption of DSG was followed by relapse in four of five occasions. Resumption of DSG led to complete remission. Currently, five of the seven patients are still treated with DSG and are in remission. Infections, mainly of the respiratory tract, were observed in five cases and resolved after treatment. One case developed a third-degree heart block that required pacing.

CONCLUSIONS

In patients with refractory Wegener's granulomatosis, prolonged treatment with DSG seems safe and successful.

Both T and non-T cells with proliferating potentials are effective in inducing suppression of allograft responses by alloantigen-specific intravenous presensitization combined with suboptimal doses of 15-deoxyspergualin

In an MHC class I-disparate combination of mouse strains, a single intravenous injection of donor spleen cells combined with 10 suboptimal doses of 15-deoxyspergualin (DSG) administration was effective in inducing donor-specific suppression of cytotoxic T-lymphocyte (CTL) responses and prolonged survival of the relevant skin allograft. Proliferative potentials of the donor spleen cells were requirement for the induction of suppressed allospecific responses, but both highly purified T cells and non-T cells were equally effective to induce the suppression of CTL responses by intravenous injection. These results have shown that, although working on different mechanisms, DSG is as effective as FK506 or rapamycin in inducing allograft tolerance when used at suboptimal doses along with the donor-specific intravenous presensitization, and an immune mechanism other than well-characterized veto T cells is working in this model in suppressing alloreactive CTL precursors.

Influence of immunosuppressive drugs on dendritic cells

Immunosuppressive drugs used to control allograft rejection and in efforts to promote transplant tolerance are well recognized for their abilities to inhibit lymphocyte activation and proliferation. In recent years, evidence has accumulated that these diversely acting agents (anti-proliferative drugs, calcineurin inhibitors, rapamycin, deoxyspergualin and glucocorticoids) also affect the development and functional immunobiology of dendritic cells, in vitro and in vivo. Here we review the influence of immunosuppressive drugs on the differentiation and function of these important antigen-presenting cells. We also consider how these effects influence immune reactivity and tolerance induction, implications for furthermore understanding of dendritic cell biology and prospects for improving the outcome of organ transplantation and therapy of other immune-mediated disorders by impacting dendritic cell function.

15-Deoxyspergualin in patients with refractory ANCA-associated systemic vasculitis: a six-month open-label trial to evaluate safety and efficacy

The combination of cyclophosphamide (CYC) and oral corticosteroids is effective in the majority of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AASV), but it carries substantial risk of drug-related morbidity and mortality. New regimens are desired, especially in refractory cases. The immunosuppressant 15-deoxyspergualin (DSG) is effective in experimental autoimmune disease and transplantation as well as in acute kidney transplant rejection in humans. To assess the efficacy and safety of DSG, an open label multicenter trial was conducted in patients with AASV who were either unresponsive or had contraindications for standard immunosuppressants. Included were 19 cases of Wegener granulomatosis and one case of microscopic polyangiitis. Nine of them had received CYC shortly before study entry without apparent therapeutic success. DSG (0.5 mg/kg per d) was given for 2 to 3 wk until the WBC count dropped to 3000/ micro l followed by a rest until at least a WBC of 4000/ micro l was reached again. This was repeated up to six cycles. During the study, no other immunosuppressants besides steroids were allowed. Disease improvement during treatment with DSG was achieved in 70% of cases (six cases of complete remission; eight cases of partial remission). Leucopenia occurred in each patient in a regular pattern during the cycles and was transient without exception. No mortality or septicemia was observed. Mild to moderate infections mainly in the respiratory tract were observed but resolved under adequate treatment without sequel. It is concluded that treatment with DSG is successful in patients with refractory Wegener granulomatosis under careful monitoring of WBC count.

The immunosuppressive agent 15-deoxyspergualin functions by inhibiting cell cycle progression and cytokine production following naive T cell activation

Immunosuppressive agents are commonly used in the prevention of graft rejection following transplantation and in the treatment of autoimmunity. In this study, we examined the immunosuppressive mechanism of the drug 15-deoxyspergualin (DSG), which has shown efficacy in the enhancement of graft survival and in the treatment of autoimmunity. Using a murine model of chronic relapsing and remitting experimental autoimmune encephalomyelitis, we were able to demonstrate that DSG both delayed and reduced the severity of experimental autoimmune encephalomyelitis. Subsequent in vitro studies to examine the mechanism of immune suppression showed that DSG was not able to inhibit early activation of naive CD4 T cells, but DSG did effectively inhibit the growth of naive CD4 T cells after activation. An analysis of cell proliferation and cell cycle showed that DSG treatment led to a block in cell cycle progression 2-3 days following Ag stimulation. In addition, DSG treatment inhibited the production of IFN-gamma by Th1 effector T cells. These studies suggest that CD4 T cells are a predominant target for DSG and the immunosuppressive effects of the drug may result from reduced CD4 T cell expansion and decreased polarization into IFN-gamma-secreting Th1 effector T cells in the induction of certain autoimmune disorders.

Induction of donor-specific allograft tolerance by short-term treatment with LF15-0195 after transplantation. Evidence for a direct effect on T-cell differentiation

A 20-day treatment with LF15-0195, a deoxyspergualine analog, induced long-term heart allograft survival in the rat without signs of chronic rejection. LF15-0195-treated recipients did not develop an anti-donor alloantibody response. Analysis of graft-infiltrating cells, IL10, TNFalpha, IFNgamma mRNA and iNOS protein expression in allografts, 5 days after transplantation, showed that they were markedly decreased in allografts from LF15-0195-treated recipients compared with allografts from untreated recipients. Surprisingly, spleen T cells from LF15-0195 recipients, 5days after grafting, were able to proliferate strongly in vitro, when stimulated with donor cells, but had reduced mRNA expression for IFNy compared with spleen T cells from untreated graft recipients. Furthermore, when T cells from naive animals were stimulated in vitro, using anti-CD3 and anti-CD28, LF15-0195 also increased T-cell proliferation in a dose-dependent fashion: however, these cells expressed less of the Th1 -related cytokines, IFNgamma and IL2, compared with untreated cells, suggesting that LF15-0195 could act on T-cell differentiation. In conclusion, we show here that a short-term treatment with LF15-0195 induced long-term allograft tolerance, decreasing the in situ anti-donor response, and we illustrate evidence for the development of regulatory mechanisms.

Reduced levels of Hsp70 result in a therapeutic effect of 15-deoxyspergualin on acute graft-versus-host disease in (DA x LEW)F1 rats

We have shown previously that increased levels of hsp70, and antibodies reactive with hsp70 parallel the onset and severity of graft-versus-host disease (GVHD) in a parent --> (DA x LEW)F1 rat model. In this study we have assessed the effect of reducing the levels of the 70 kDa heat shock protein (hsp70), on the morbidity and mortality of acute GVHD in (DA x LEW)F1 rats. The reduction was accomplished by the administration of 15-deoxyspergualin (DSG), an immunosuppressive agent which binds to a constitutively expressed member of the 70 kDa heat shock protein family. DSG administered via three different protocols reduced GVHD-associated morbidity. One of the regimens, which consisted of intermittent DSG administration, also significantly reduced GVHD associated mortality. This DSG treatment reduced hsp70 levels in spleen and lymph nodes, inhibited anti-hsp70 antibody production, and diminished the serum levels of IL-2, IFN-gamma, TNF-alpha, and IL-10. IL-4 levels in the serum did not change during GVHD and were not effected by DSG. These results show that the mechanism of DSG immunosuppressive effect in rat GVHD may involve DSG's capacity to bind to hsp70, which in turn may lead to a decrease in levels of circulating anti-hsp70 antibodies, and reduced production of cytokines.

The HSC73 Molecular Chaperone: Involvement in MHC Class II Antigen Presentation

Heat shock proteins (HSP) are conserved proteins, many of which share the ability for indiscriminate peptide binding and ATPase-coupled peptide release. In this paper, we show that heat shock cognate protein (HSC)73, a constitutively expressed member of the HSP70 family, could be a candidate for chaperone activity within the MHC class II presentation pathway. HSC73 expression in macrophages was shown to overlap with expression of MHC class II; overexpression of HSC73 in stable transfectants of a macrophage line markedly enhanced their presentation of exogenous Ag without affecting presentation of processing independent peptide. Ag from an exogenous source was demonstrated to associate with HSC73 in macrophages, and this association was sensitive to ATP treatment and inhibited by deoxyspergualin, an immunosuppressive agent that has previously been shown to bind specifically to HSC73. Furthermore, deoxyspergualin reduced Ag presentation by macrophages in relation to the amount of HSC73 expressed in these cells. The data are consistent with a potential role for HSC73 in binding and protecting peptides from extensive degradation and/or facilitating the kinetics of peptide transfer to MHC class II molecules.

T cell repertoire expression in murine recipients of bone marrow transplant after LF 08-0299 (Tresperimus) administration

LF 08-0299 (Tresperimus), a novel immunosuppressive compound, has been previously shown to prevent graft-versus-host disease in murine models. In this study, we investigated the influence of LF 08-0299 on the TCR Vbeta repertoire of irradiated F1 recipient mice reconstituted with either syngeneic or parental bone marrow cells. We showed that a partial blockade of thymic differentiation occurred in normal mice under treatment at the transition CD4-/CD8- to CD4+/CD8+, and that this blockade was fully reversible. Despite the effect on the thymus, normal T cell repertoire negative selection was preserved following syngeneic bone marrow transplantation. We further assessed whether LF 08-0299 administration could modify Vbeta T cell expression in irradiated recipients reconstituted with parental bone marrow cells. In our murine parental to F1 transplant model, abnormal TCR Vbeta3, Vbeta5, Vbeta6 and Vbeta11 expression was demonstrated in peripheral lymph nodes of irradiated recipients. Moreover, Vbeta6 and Vbeta3 T cell populations were overexpressed. Administration of LF 08-0299 modified the pattern of Vbeta T cell expression. The expansion of Vbeta6 T cells was selectively inhibited under LF 08-0299 therapy and, in contrast, Vbeta5 T cells were overexpressed. Lymph node histological analysis showed that LF 08-0299 administration fully prevented the graft-versus-host reaction occurring in untreated recipient mice.

Immunosuppressant deoxyspergualin induces apoptotic cell death in dividing cells

Deoxyspergualin (DSG) has been found to have an antitumour and immunosuppressive activity. However, the precise mechanism of action of DSG has not been clarified. We have used its analogue, methyldeoxyspergualin (MeDSG) for in vitro culture studies of DSG since it shows good stability in aqueous solution and retains strong immunosuppressive activity. In the present study, we found that MeDSG inhibited proliferation of rapidly dividing murine T-cell hybridomas, resulting in cell death. The cell death was accompanied by chromatin condensation and DNA cleavage at the linker regions between nucleosomes. Furthermore, MeDSG induced a reduction in mitochondrial transmembrane potential. When murine thymocytes were treated with MeDSG for 48 hr, a slight increase of DNA fragmentation was constantly observed, and selective depletion of CD4- CD8- cells was noticed. In contrast, CD4+ CD8+ cells were hardly affected. Moreover, splenic T-cells are resistant to MeDSG-induced apoptosis, as evaluated by measuring DNA cleavage. Our findings may account for the immunosuppressive and antitumour properties of DSG which were described in a number of previous studies.

Deoxyspergualin preferentially inhibits the growth and maturation of anti-CD40-activated surface IgD+ B lymphocytes

Deoxyspergualin (DSG), an analogue of spermidin, is a potent immunosuppressive drug with an action quite distinct from that of cyclosporin, rapamycin, or FK506. In this study we investigated the effect of DSG and methyldeoxyspergualin (MeDSG) on the proliferation and differentiation of human B cells stimulated with anti-CD40 MoAb. Highly purified B cells obtained from tonsillar samples were used as target cells. Both agents inhibited the proliferative response of anti-CD40-stimulated B cells in the absence and presence of IL-4, IL-2 or IL-10 in a dose-dependent manner. This inhibitory effect differed markedly among cell populations based on surface IgD expression: strong inhibition of sIgD+ B cells but little inhibition of sIgD- B cells. The drugs also suppressed the production of IgG, IgM and IgA by unfractionated B cells, which suggests that DSG acts against post-switch (sIgD-) B cells. Although the drugs suppressed immunoglobulin synthesis by both sIgD+ and sIgD- B cells, the effect was more marked in the sIgD+ B cells. Analysis of the subclass of IgG secreted by sIgD+ B cells revealed a decline in IgG1 and IgG3 in the presence of DSG. These results suggest that DSG preferentially inhibits the growth and maturation of sIgD+ naive B cells.

Deoxyspergualin neither counteracts lipopolysaccharide (LPS) or Staphylococcus aureus enterotoxin-B (SEB) induced lethality in mice nor does it modulate the release of tumor necrosis factor-alpha

To gain further insights into the immunopharmacological mode of action of the immunosuppressant antibiotic deoxyspergualin (DSP), its effects were evaluated in murine lethal endo- and exotoxemia. These are two cytokine-mediated macrophage and T cell dependent immunoinflammatory conditions that can be induced in D-Galactosamine (D-Gal) presensitized mice by the injections with either LPS or SEB, respectively. The results show that prophylactic treatment with DSP (2.5 or 5 mg/kg bd.wt. 48, 24 and 2 h prior to challenge) neither improved the rate of survival, nor influenced the massive increase in the blood levels of tumor necrosis factor-alpha which followed the challenge with LPS or SEB. In sharp contrast, these clinical and seroimmunological events were both markedly counteracted by prophylactic treatment with sodium fusidate, another immunosuppressive agent used as control.

Organ-specific disease provoked by systemic autoimmunity

Rheumatoid arthritis (RA) is a chronic joint disease characterized by leukocyte invasion and synoviocyte activation followed by cartilage and bone destruction. Its etiology and pathogenesis are poorly understood. We describe a spontaneous mouse model of this syndrome, generated fortuitously by crossing a T cell receptor (TCR) transgenic line with the NOD strain. All offspring develop a joint disease highly reminiscent of RA in man. The trigger for the murine disorder is chance recognition of a NOD-derived major histocompatibility complex (MHC) class II molecule by the transgenic TCR; progression to arthritis involves CD4+ T, B, and probably myeloid cells. Thus, a joint-specific disease need not arise from response to a joint-specific antigen but can be precipitated by a breakdown in general mechanisms of self-tolerance resulting in systemic self-reactivity. We suggest that human RA develops by an analogous mechanism.