Rita Gottschalk

Prevention and cure of autoimmune diabetes in nonobese diabetic mice by continuous administration of FTY720

Background. Treatment of nonobese diabetic (NOD) mice with FTY720 before the development of insulitis prevents the onset of diabetes. In this study, the authors investigated whether FTY720 treatment of NOD mice with established insulitis prevents the development of diabetes. Methods. FTY720 (1 mg/kg) was administered continuously to euglycemic NOD mice starting at 14 or 23 weeks of age. A group of untreated, age-matched NOD mice served as controls. Mice with more than 300 mg/dL blood glucose on three consecutive measurements were considered diabetic. Results. Diabetes developed in control mice starting at 13 weeks of age and reached 78% by 33 weeks of age. Mice at 14 and 23 weeks of age exhibited extensive insulitis that progressed with age. Continuous oral administration of FTY720 starting at either age completely prevented the development of diabetes. However, its withdrawal at 37 weeks of age led to abrupt diabetes onset. Pancreases of FTY720-treated diabetes-free mice showed peripheral insulitis, with strong insulin staining. The protection from diabetes was also achieved by intraperitoneal injection of FTY720 or sirolimus (1.5 mg/kg). Unlike FTY720, withdrawal of sirolimus did not induce diabetes. Continuous oral FTY720 (3 mg/kg) treatment in overtly diabetic NOD mice led to complete reversal of diabetes in 6 of 11 mice. The standard adoptive transfer study in NOD-severe combined immunodeficient mice showed that peripheral lymphoid organs of FTY720-treated mice contained diabetogenic cells but not dominant immunoregulatory cells. Conclusions. FTY720, which does not cause generalized immunosuppression, may be a safe and benign therapeutic agent for chronic use to prevent or cure type 1 diabetes.

Establishment of stable multilineage hematopoietic chimerism and donor-specific tolerance without irradiation.

BACKGROUND Induction of tolerance to organ transplants will increase graft survival and decrease patient mortality and morbidity. Radiation-induced cytoreduction/ablation followed by donor hematopoietic cell reconstitution has been the most consistently successful approach to experimental tolerance induction. However, reluctance of clinicians to expose recipients to radiation has hampered its clinical application. METHODS In the studies described, administration of polyclonal antilymphocyte serum (ALS), donor-specific bone marrow (DSBM) (150x10(6) cells), and sirolimus (24 mg/kg) in a completely mismatched murine model (B10.A donor, C57B/10 recipient) produced 100% indefinite (>250 days) skin graft survival. The level and character of donor-specific chimerism was evaluated with flow cytometry. RESULTS Specific tolerance was confirmed by continued acceptance of primary and secondary donor-specific skin allografts and rejection of third-party grafts. The level and duration of chimerism induced was directly related to the dose of DSBM administered. Mice given 150x10(6) DSBM cells showed levels of 8-10% donor peripheral blood mononuclear cell chimerism by 30 days, and these levels persisted indefinitely (>250 days) in association with permanent tolerance of donor grafts. Eighty percent of donor chimeric cells were B lymphocytes (MHC class I and II positive, Fc receptor positive, CD45/B220 positive but negative for CD4, CD8 and Thy 1.2) and 20% were sorted in the macrophage monocyte population. CONCLUSIONS These studies demonstrate for the first time that cytoreduction/ablation with ALS combined with sirolimus and reconstitution with donor bone marrow induces tolerance and chimerism in a completely mismatched murine combination. The use of ALS and sirolimus, currently employed therapies in clinical transplantation, and the lack of requirement for radiation make this tolerance protocol attractive for clinical application.

Use of CTLA4-Ig in combination with conventional immunosuppressive agents to prolong allograft survival

BACKGROUND The objective of our study was to determine the effectiveness of CTLA4-Ig, a novel immunosuppressive agent, in augmenting allograft survival when combined with either cyclosporine, sirolimus, donor-specific bone marrow alone (BM), or bone marrow in conjunction with antilymphocyte serum (ALS). METHODS Full-thickness skin allografts were used in C3H to B6AF1 (class I mismatch) and AKR to C57BL/6 (complete mismatch) models. Groups of mice (n=6-14) were treated with various combinations of the following treatment protocols: murine CTLA4-Ig, L-6 control Ig, sirolimus, cyclosporine, ALS, or ALS/BM. RESULTS In the class I mismatch model, L-6 control Ig had no effect whereas use of CTLA4-Ig alone resulted in a doubling of the median graft survival compared with controls. The addition of either sirolimus or cyclosporine to CTLA4-Ig increased graft survival over that achieved with CTLA4-Ig alone. CTLA4-Ig demonstrated no efficacy when used in combination with BM, ALS, or ALS/BM. CTLA4-Ig was clearly less effective in the complete mismatch model. CONCLUSION These data suggest that CTLA4-Ig may be effective clinically in combination with cyclosporine or sirolimus but offers no additional effectiveness in combination with antilymphocyte serum with or without donor-specific bone marrow.

The effect of injection of donor bone marrow on the frequency of donor-reactive CTL in antilymphocyte serum-treated, grafted mice.

The survival of C3H/He skin grafts can be prolonged on B6AF1 mice immunosuppressed with ALS by the injection of C3H/He marrow 1 week postgrafting. The precursor frequencies of donor-reactive CTL in the spleen and lymph nodes of ALS-treated, grafted mice given donor marrow were compared with CTL frequencies observed in ALS-treated, grafted controls. Spleens and nodes were removed from experimental and control mice on days +8, +14, +21, +58, and 1 year postgrafting, and used as effectors in the LDA. Donor-reactive CTL in the marrow-injected group remained suppressed as long as the recipients maintained their grafts. The frequency of CTL to third-party antigens was normal in mice bearing long-term C3H/He grafts. When marrow-injected mice rejected their grafts, the total donor-reactive CTL frequency returned to normal. In contrast, in ALS-treated controls that did not receive marrow, the total number of donor-reactive CTL returned to normal levels with recovery from the immunosuppressive effects of ALS. These results suggest that donor marrow suppresses the regeneration of donor-reactive CTL in the lymphoid tissues of ALS-treated mice, possibly by veto cell activity.

EFFECT OF BLOOD TRANSFUSION ON IL-2 PRODUCTION

Spleen cells from B10.A mice transfused with B10.D2 blood suppress the immune responses of normal B10. A to B10.D2 in coculture as early as 2 days posttransfusion. In addition, the ability of B10.A mice to respond in cell-mediated lymphocytotoxicity (CML) is significantly impaired as early as 2 days after B10.D2 transfusion. Experiments were performed to characterize the cells mediating the suppressive effect and to determine whether the inability of transfused mice to generate a cytotoxic response is due to an inhibition of IL-2 production. To characterize the suppressor cells, spleen cells from B10.A mice were assayed 2 or 16 days after B10.D2 transfusion for the ability to suppress mixed lymphocyte culture (MLC) and CML responses of normal B10.A mice in coculture. The putative suppressor cells were either passed over a Sephadex G-10 or nylon wool column, treated with anti-Thy antibody or left untreated before addition to the coculture. Untreated cells from transfused mice suppressed the CML response of normal B10.A both 2 and 16 days posttransfusion, while the effect on the MLC response was inconsistent. Passage of the cells over Sephadex G-10 or nylon wool before assaying abrogated the suppressive effect, while treatment with anti-Thy antibody had no effect. These results suggest that the suppressor cells appearing shortly after blood transfusion have the characteristics of macrophages and not T lymphocytes. To determine the effect of transfusion on IL-2 production, cells from transfused mice were assayed for their ability to produce IL-1 and IL-2 and for the formation of IL-2 receptors. In addition, the effect of exogenous IL-1 and IL-2 on restoring the CML response of transfused mice to normal was assayed. The production of IL-1 by transfused mice was normal, while the production of IL-2 was significantly suppressed both 2 and 16 days posttransfusion. Activated cells from normal and transfused mice showed equal ability to absorb IL-2, indicating that IL-2 receptor formation is normal after transfusion. The addition of exogenous IL-2, but not IL-1, to CML cultures containing cells from transfused mice as responders restored the response to normal. These results indicate that the inability of transfused mice to respond in CML is due, at least in part, to an inability to produce IL-2. This could be mediated by prostaglandins released by activated macrophages.

Determination of an improved sirolimus (rapamycin)-based regimen for induction of allograft tolerance in mice treated with antilymphocyte serum and donor-specific bone marrow.

BACKGROUND Posttransplant donor-specific bone marrow (BM) infusion in mice treated with antilymphocyte serum (ALS) induces specific unresponsiveness (tolerance) to skin allografts, which can be augmented by the adjuvant administration of chemotherapeutic immunosuppressive agents. The purpose of this study was to determine the optimal dose and timing of administration of sirolimus (rapamycin) to induce maximal skin allograft survival in ALS-treated, BM-infused recipients. METHODS DBA/2 donor skin grafts were placed on B6AF1 recipients (class I- and II-disparate). Groups of recipient mice (n=10 each) received combinations of the following treatment protocols: ALS, 0.5 ml on days -1 and 2; BM, 25x10(6) donor-specific cells on day 7; sirolimus, 6, 12, 18, or 24 mg/kg at times indicated; and cyclosporine, 50 mg/kg at times indicated. The immune status of putatively tolerant animals was examined with mixed lymphocyte cultures, cell-mediated lympholysis assays (CML), and limiting dilution analyses. RESULTS When administered in conjunction with ALS/BM, a single dose of sirolimus (6 mg/kg) on days 21, 18, 14, 10, or 7 resulted in median skin graft survival times of 35, 26, 40, 46, and 103 days, respectively, versus a median survival of 27 days in mice given ALS and BM alone. The addition of cyclosporine to sirolimus (6 mg/kg) given on day 7 or days 7 and 10 did not significantly increase graft survival over that achieved with sirolimus alone. A single dose (18 or 24 mg/kg) of sirolimus administered on day 7 to ALS/BM-treated recipients resulted in 100% 200-day skin graft acceptance. Tolerant mice demonstrated nonspecific suppression of the mixed lymphocyte culture assays at 90 and 200 days and a nonspecific reduction of the CML assay at 50 days. By 200 days, the third-party CML response was restored, whereas donor-specific cell-mediated cytotoxicity remained suppressed. There was a donor-specific reduction in the number of alloreactive cytotoxic T lymphocyte clones by limiting dilution assay at 120 days. In vivo specificity of immunosuppression induced with this protocol was demonstrated by indefinite survival of second donor-specific skin grafts placed on putatively tolerant mice at day 90, whereas third-party skin grafts were rejected in 14 days. CONCLUSION A single dose of sirolimus (18-24 mg/kg) administered on day 7, within the context of an ALS/BM immunosuppressive regimen, reliably induces permanent skin allograft acceptance in this model. In vitro measures of immunocompetence demonstrated an early nonspecific suppression of the recipients immune status and later recovery of third-party immunoreactivity. In vivo testing indicates an operationally tolerant state that is donor-specific 90 days after treatment.

Superiority of sirolimus (rapamycin) over cyclosporine in augmenting allograft and xenograft survival in mice treated with antilymphocyte serum and donor-specific bone marrow.

BACKGROUND Sirolimus is a potent immunosuppressive agent with great therapeutic potential. The objective of our study was to evaluate the efficacy of sirolimus versus cyclosporine in augmenting the unresponsiveness induced by an antilymphocyte serum (ALS)/donor-specific bone marrow (BM)-based regimen across three levels of histoincompatibility: class I and II disparate (DBA/2 to B6AF1), complete mismatch (AKR to C57BL/6), and xenograft (ACI rat to B6AF1). METHODS Full-thickness skin grafts were taken from donors and placed on recipients in standard fashion. Seven groups of recipient mice (n=10-28) received various combinations of the following treatment protocols: sirolimus, 1.5 mg/kg (3.0 mg/kg for xenografts) every other day from day 0 to day 12; cyclosporine, 50 mg/kg every other day from day 10 through 22; ALS, 0.5 ml on days -1 and 2 for allografts and days -1, 2, and 4 for xenografts; and BM, 25 million donor-specific cells IV on day 7. RESULTS The administration of ALS or ALS/BM resulted in modest but significant prolongation of skin graft survival in all combinations tested. Cyclosporine combined with ALS or ALS/BM significantly extended allograft survival compared with ALS or ALS/BM alone (P<0.05) but had no effect on xenograft survival. In contrast, the combination of sirolimus with ALS or ALS/BM resulted in a two- to threefold increase in allograft survival and over a fourfold increase in xenograft survival when compared with the comparable cyclosporine-based regimen. Additionally, lymphocytes isolated from class I and II incompatible mice with skin grafts surviving >100 days demonstrated markedly reduced interleukin 2 and interferon-gamma secretion in response to irradiated donor-specific lymphocytes in culture. CONCLUSIONS In the regimens tested, sirolimus was superior to cyclosporine in augmenting donor BM-induced skin graft prolongation in ALS-treated mice across all levels of histoincompatibility.

Prevention of graft-versus-host disease following small bowel transplantation with polyclonal and monoclonal antilymphocyte serum : the effect of timing and route of administration

Graft-versus-host disease is a potential problem following small bowel transplantation. We have previously shown that a two-day intraperitoneal course of polyclonal antilymphocyte serum completely prevents GVHD without impairing allograft function in a unidirectional rat small bowel transplant model. In the present study we sought to determine the optimum route and timing of ALS administration and whether donor pretreatment with the anti—T cell receptor monoclonal antibody R73 would be similarly effective in preventing GVHD. Both intravenous and intraperitoneal injection of ALS effectively prevent GVHD in this model. ALS must be given to donors at least 48 hr prior to graft procurement for maximum effectiveness. Prevention of GVHD correlates with lymphocyte depletion in mesenteric lymph nodes, as opposed to peripheral blood or small bowel lamina propria. Donor pretreatment with the monoclonal antibody R73 significantly delays the onset of GVHD in this small bowel transplant model but appears less effective than polyclonal ALS.

Characterization of spleen cells capable of inducing unresponsiveness in ALS-treated mice.

C3H/He skin allografts are significantly prolonged in ALS-treated B6AF1 mice by the injection of 50 x 10(6) C3H/He spleen cells 1 week postgrafting. To identify and characterize the spleen cell active in promoting graft survival, C3H/He spleen cells were separated on a discontinuous Percoll gradient and the various fractions were assayed for the ability to prolong skin graft survival in ALS-treated B6AF1 mice. In addition, unfractionated spleen and spleen fractions were depleted of specific cell populations before injection to determine the effect of various cell populations on graft prolongation. The active cell was recovered primarily in the 52.5% Percoll fraction. Cells in the 60% fraction also had a graft-prolonging effect, but not as significant as that of the 52.5% fraction. Depletion of Thy 1, Ia and Ig-positive cells from unfractionated spleen or spleen fractions did not decrease the graft-prolonging effect. Both Fc gamma R-positive and Fc gamma R-negative cells prolonged graft survival, but the Fc gamma R- cells were the most effective. In contrast to the effect of spleen cells, lymph node cells and thymocytes are relatively ineffective in prolonging graft survival in ALS-treated mice. When lymph node lymphocytes and thymocytes were separated on a Percoll gradient, the cell population active in prolonging graft survival was recovered primarily in the 52.5% fraction. Treatment of the 52.5% fraction of lymph node lymphocytes or thymocytes with monoclonal antibody to Thy 1 before injection abrogated the graft-prolonging effect. These results indicate that the spleen cell(s) active in prolonging graft survival in ALS-treated mice is a non-T, non-B cell, as it lacks Thy 1, Ia, and Ig surface markers. Both Fc gamma R+ and Fc gamma R- spleen cells are effective in prolonging grafts, but Fc gamma R- cells are the most effective. In contrast, the active cell in lymph node and thymus is Thy 1-positive, indicating that it is a T lymphocyte.

Marked prolongation of rat skin xenografts induced by intrathymic injection of xenogeneic splenocytes and a short course of rapamycin in antilymphocyte serum-treated mice.

The effect of intrathymic (IT) injection of donor splenocytes and a short course of rapamycin (Rapa) treatment on rat to mouse skin xenograft survival was investigated. ACI rat skin xenografts were transplanted to (C57BL/6 x A)F1 mice treated with rabbit anti-mouse lymphocyte serum (ALS) on days -1, +2, and +4 relative to skin grafting on day 0. Fifty million donor-type splenocytes were injected intrathymically on day 7 after transplantation. Rapa was given intraperitoneally every other day from day 0 to day 12 at a dose of 3.0 mg/kg. Prolonged skin xenograft survival was observed in ALS- and Rapa-treated recipients (no IT injection) with a median survival time of 47 days. However, skin graft survival was markedly more prolonged in the group treated with ALS, Rapa, and IT injection of donor splenocytes did not have a beneficial effect on skin xenograft survival in ALS-treated recipients. An increased presence of donor-type cells was observed in the thymus of the ALS- and Rapa-treated recipients for 7 days after IT injection of donor splenocytes. In conclusion, a short course of Rapa markedly augments rat skin xenograft survival in ALS-treated mice injected intrathymically with donor-type splenocytes.