Influence of a radioprotector WR-638 on the lymphoid compartment of the irradiated rat thymus: a flow cytometric analysis

The T cell composition of the thymus of X-ray irradiated (3.5 Gy) Wistar rat protected with WR-638 was analyzed by flow cytometry using monoclonal antibodies directed to the Thy 1.1, CD43, CD2, CD5, CD4, CD8 and class I and II MHC antigens. It was shown that this dose of X-rays caused cyclic changes in thymic cellularity manifested as: primary involution (until day 2), primary regeneration (from days 2 to 14), secondary involution (from days 14 to 21) and secondary regeneration (from days 21 to 30). WR-638 reduced the magnitude of thymocyte depletion in the primary involutive phase of the irradiated thymi, primarily as a result of protection of Thy 1.1high+ CD2low+ CD5high+ CD4+ CD8+ class I antigen high+ subpopulations of thymocytes. In the early regenerative phase, WR-638 accelerated the regeneration of CD4-CD8- and CD4-CD8+ thymocyte subsets, followed by subsequent increase of CD4+CD8+ and CD4+CD8- thymocyte subsets. Secondary involutive and regenerative phases in protected animals were characterized by higher absolute cell number of almost all thymocyte subpopulations in comparison with those in irradiated, non-protected animals.

Hyperfractionated total lymphoid irradiation and cyclophosphamide for preparation of previously transfused patients undergoing HLA-identical marrow transplantation for severe aplastic anemia

PURPOSE

To assess the immunosuppressive capacity of hyperfractionated total lymphoid irradiation and cyclophosphamide for transplantation of unmodified allogeneic marrow in sensitized aplastic anemia patients.

METHODS AND MATERIALS

From February 1983 to September 1990, 23 multiply transfused aplastic anemia patients underwent unmodified bone marrow transplantation from HLA genotypically identical sibling donors following preparation with 6 Gy hyperfractionated total lymphoid irradiation and 160 mg/kg cyclophosphamide. Graft-versus-host disease prophylaxis included steroids in one patient, methotrexate in four, cyclosporine in seven, and methotrexate/cyclosporine in 12. There were 17 males and 6 females with a median age of 13 (range: 2.5-32).

RESULTS

One patient died early before engraftment of bacterial sepsis. Twenty-two patients were evaluable for engraftment. Three experienced graft failure including one primary, and two late graft failures associated with cyclosporine withdrawal. Acute graft-versus-host disease occurred in 7/22 (> or = grade II in 6), and chronic graft-versus-host disease in 3/17 patients. Except for a patient who received total body irradiation for a second transplant, no patient in this series developed interstitial pneumonia. Fifteen patients are alive with follow-up of 38-125 months (median 68). The overall actuarial survival at 5 years is 69%, at 8 years it is 60%, with one late death. The survival of adult patients was similar to that of younger patients (> or = 16 years old: 63%, < 16 years old: 55%). The development of acute graft-versus-host disease adversely influenced survival (88% with Grade 0-I, 17% with grade II-IV; p = 0.002). No hypothyroidism or secondary malignancies have been documented in this series.

CONCLUSION

Pretransplant immunosuppression with 6 Gy of hyperfractionated total lymphoid irradiation and 160 mg/kg CY reduces but does not eliminate the incidence of graft failure in sensitized aplastic anemia patients. The dose and the mode of administration of total lymphoid irradiation in this trial may be associated with a lower incidence of late side effects. Survival is comparable to that obtained using preparative regimens without radiation.

Nonspecific mixed lymphocyte culture inhibitory antibodies in sera of tolerant transplanted baboons conditioned with total lymphoid irradiation

Pretransplant conditioning of baboons with total lymphoid irradiation allows long-term renal allograft acceptance in one third of the recipients. Brief additional immunosuppression was given to some animals, but always for less than 14 days after transplant. This enabled us to study mechanisms of graft tolerance in the absence of long-term, nonspecific drug immunosuppression. While 3 patterns of unresponsiveness were noted, this study concentrated on serum-mediated suppression. Eleven of 16 (69%) baboons destined to become tolerant to their grafts developed a nonspecific MLC inhibitory factor in their sera. In most animals it appeared within 3-5 weeks after transplantation and persisted over the period of study (91-793 days after Tx). The suppressor factor was absent in sera from 38 control animals and 8/9 rejectors. It was shown to be a low affinity IgG antibody that inhibited MLC by binding to stimulator cells, an effect that could be overcome by addition of rIL-2 to cultures. NK cell lysis, cell-mediated lympholysis, and polyclonal mitogenesis were unaffected. Antibody binding to purified baboon T cells could not be demonstrated, though binding to EBV-transformed B cells was readily shown. Our study shows that total lymphoid irradiation permits the generation of blocking antibodies directed against APCs as one mechanism of maintaining T cell unresponsiveness. These observations are consistent with the masking of ligands involved in antigen presentation or costimulation leading to a sustained state of autoenhancement.

Effect of total lymphoid irradiation on natural killer cells and cytotoxic and primed T lymphocytes

Total lymphoid irradiation (TLI), which results in prolonged depression of the number and function of T and B cells, augments the natural killer (NK) cell activity. Small doses of irradiation (200-400 cGy) in vitro did not reduce the lytic activity of TLI-induced NK cells, whereas irradiation with 1,500 and 3,000 cGy decreased NK function by 50-70%. Addition of TLI spleen cells, containing a high proportion of large mononuclear cells, to cytotoxic T lymphocytes (CTL), generated in vitro by one-way mixed lymphocyte reaction and tested against 51Cr labeled target cells, suppressed the lytic activity 27-57% of that observed following the addition of normal spleen cells. The suppressive effect induced by spleen cells of TLI-treated mice was H2 nonrestrictive. Primed T lymphocytes (PTL) stimulated with irradiated allogeneic cells were inhibited by cocultured TLI spleen cells, causing inhibition of 57% as measured by secondary proliferative response and 86% inhibition by primary response to a third strain of cells. Our results, together with previously published data, indicate that TLI-induced suppressor cells inhibit the generation of PTL and CTL. Secondary proliferative responses of T cells primed to alloantigens are suppressed, as is the lysis of target cells by CTL. All suppressive phenomena presented here are antigen nonspecific.

Ionizing radiation and autoimmunity. Induction of autoimmune disease in mice by high dose fractionated total lymphoid irradiation and its prevention by inoculating normal T cells

Ionizing radiation can functionally alter the immune system and break self-tolerance. High dose (42.5 Gy), fractionated (2.5 Gy 17 times) total lymphoid irradiation (TLI) on mice caused various organ-specific autoimmune diseases, such as gastritis, thyroiditis, and orchitis, depending on the radiation dosages, the extent of lymphoid irradiation, and the genetic background of the mouse strains. Radiation-induced tissue damage is not the primary cause of the autoimmune disease because irradiation of the target organs alone failed to elicit the autoimmunity and shielding of the organs from irradiation was unable to prevent it. In contrast, irradiation of both the thymus and the peripheral lymphoid organs/tissues was required for efficient induction of autoimmune disease by TLI. TLI eliminated the majority of mature thymocytes and the peripheral T cells for 1 mo, and inoculation of spleen cell, thymocyte, or bone marrow cell suspensions (prepared from syngeneic nonirradiated mice) within 2 wk after TLI effectively prevented the autoimmune development. Depletion of T cells from the inocula abrogated the preventive activity. CD4+ T cells mediated the autoimmune prevention but CD8+ T cells did not. CD4+ T cells also appeared to mediate the TLI-induced autoimmune disease because CD4+ T cells from disease-bearing TLI mice adoptively transferred the autoimmune disease to syngeneic naive mice. Taken together, these results indicate that high dose, fractionated ionizing radiation on the lymphoid organs/tissues can cause autoimmune disease by affecting the T cell immune system, rather than the target self-Ags, presumably by altering T cell-dependent control of self-reactive T cells.

Total lymphoid irradiation, anti-lymphocyte globulin and Campath 1-G for immunosuppression prior to bone marrow transplantation for aplastic anemia after repeated graft rejection

Allogeneic BMT for severe aplastic anemia is associated with a significant rate of graft rejection, especially in patients who have been previously transfused. We report a child with aplastic anemia who rejected donor marrow twice despite adequate immunosuppression as part of the conditioning therapy but engrafted successfully following combined administration of three modalities of immunosuppression: antithymocyte globulin, total lymphoid irradiation and the monoclonal antibody Campath-1G. Restriction fragment length polymorphism studies > 1 year after BMT show full donor hematopoiesis with no evidence of autologous recovery.

Induction of tolerance to heart allografts in rats using posttransplant total lymphoid irradiation and anti-T cell antibodies

This study examined whether posttransplant anti-T cell monoclonal or polyclonal antibody therapy could provide a window of treatment to allow posttransplant total lymphoid irradiation (TLI) to induce tolerance. These experiments were conducted in a high responder strain combination of an ACI cardiac allograft into a Lewis rat. In this situation, treatment with antibody or posttransplant TLI alone is insufficient to induce tolerance, while similar treatments alone have been shown to induce tolerance in low responder strains. The affects of three anti-T cell therapies were compared: anti-CD4 mAb therapy, anti-CD3 mAb, and rabbit antithymocyte globulin (RATG). None of these antibody therapies alone prolonged graft survival indefinitely. Combining anti-CD4 therapy with posttransplant TLI markedly delayed rejection but failed to induce long-term graft survival. Tolerance could be induced by a combination of anti-pan T cell antibody (anti-CD3) and TLI, and, all grafts survived beyond 100 days. RATG failed to prevent graft rejection when used alone or in combination with TLI. However, posttransplant therapy with a combination of RATG, TLI, and single-donor blood transfusion resulted in graft survival beyond 100 days. Recipients bearing long-term donor grafts rejected third-party (PVG) grafts within 2 weeks. Low density donor bone marrow cells used instead of a blood transfusion did not facilitate tolerance. The results indicate that monoclonal or polyclonal anti-pan T cell antibodies, TLI, and a donor blood cell infusion function synergistically in facilitating tolerance to allografts in the posttransplant period.

[Comparative study of the effect of radiation and other lymphatic agents on lymphoid tissue of dogs and rats: chromatin degradation, DNA and protein synthesis in cells]

It is established that lymphatic tissue of dogs shows far less degradation of chromatin after whob body irradiation (6 Gy) or exposure to lympholytic agents (hydrocortisone and colchicine), compared to rats. The fragmentation of chromatin in dog thymus occurs, like in rat, according to the internucleosome type, but affects a considerably less part of the thymocyte population.

Nonhuman primate responses to murine and humanized OKT4A

A nonhuman primate antimurine response (MAMA) has been observed in 17 cynomolgus renal allograft recipients of murine OKT 4A. Neither cyclosporine, nor total-lymphoid irradiation, nor donor bone marrow preparation inhibited this antixenogeneic response. In an attempt to alter the antimurine basis of the response, a humanized chimeric OKT4A (IgG4) containing the entire variable portion of the murine OKT4A and a humanized CDR grafted OKT4A mAb sharing only the Complementarity Determining Region from the murine OKT4A, were administered to 8 cynomolgus allograft recipients. MAMA was detected in each recipient. In contrast to sera from recipients of murine OKT4A, sera from recipients of humanized OKT4A displayed no reactivity to other murine mAbs. MAMA specificity did not assay constant (C) region differences between the murine and humanized mAb; however, C region homology in humans should preclude a human antimouse antibody (HAMA) to the Fc portion of a humanized mAb. Furthermore, cynomolgus recipient serum levels of the humanized OKT4A mAb were maintained (> 1 microgram/ml) for a longer period than following treatment with murine OKT4A (murine < 12 days versus between 12 and 24 days for the humanized). If the HAMA response to humanized mAb in future clinical trials, were to be predictably anti-idiotypic, then the opportunity for treatment with sequential mAbs of differing idiotypes would be retained. Moreover, these current studies also suggest that humanized construction may influence the duration of therapeutic mAb levels. Thus, anti-idiotypic reactivity may not be as consequential to the clinical administration of humanized mAb to allograft recipients.

Is aggressive therapy effective for lupus?

Intravenous cyclophosphamide is an effective form of aggressive therapy for the management of a wide range of serious manifestations of systemic lupus erythematosus. Although it has been best studied in patients with progressive lupus nephritis, recent evidence indicates an important role for this therapy for other clinical lupus indications, particularly acute neurologic diseases. The available comparative data suggest that intravenous cyclophosphamide is far more effective than intensive corticosteroid therapies, including conventional high-dose oral therapy as well as bolus intravenous therapy. Differences in efficacy compared with oral regimens of cyclophosphamide or azathioprine are less clear, although clinical experience would seem to suggest that intravenous cyclophosphamide has a more rapid onset of action clinically than low-dose oral therapies. Finally, the toxicity profile of intravenous cyclophosphamide compares favorably with other aggressive approaches to drug management and does not pose an unacceptable risk. The future impact of several current investigational therapies remains to be defined.

Total lymphoid irradiation for treatment of drug resistant chronic GVHD

We report our experience with total lymphoid irradiation (TLI) in three patients with GVHD which had failed to respond to standard drug treatment. The clinical manifestations of GVHD markedly improved with TLI treatment.

Sunlight and skin-associated lymphoid tissues (SALT): if UVB is the trigger and TNF alpha is its mediator, what is the message?

The damaging effects on cutaneous immunity of low-dose ultraviolet B (UVB) radiation in sunlight are genetically determined in mice. Polymorphic alleles at the Tnf alpha and Lps loci dictate whether mice are UVB susceptible or resistant, i.e., develop contact hypersensitivity or not when hapten is painted on UVB-exposed skin. In mice, UVB susceptibility is mediated almost exclusively by tumor necrosis factor-alpha (TNF alpha). Circumstantial evidence implicates urocanic acid (UCA) in the stratum corneum as the photoreceptor for UVB, and recent results suggest that cis-UCA in turn instigates the intraepidermal accumulation of TNF alpha. It is hypothesized that TNF alpha interrupts the induction of contact hypersensitivity by preventing epidermal Langerhans cells from carrying hapten to the draining lymph node, where activation of naive, hapten-specific T cells must first occur. The phenotypic traits of UVB susceptibility (UVB-S) and UVB resistance (UVB-R) have now been documented in human beings, and the frequency of UVB-S is high (approximately 40-45%) in both Caucasians and individuals with deeply pigmented skin. Because the frequency of UVB-S is extremely high in patients with biopsy-proved basal and squamous cell skin cancer, this trait appears to be a risk factor for this disease. The unexpectedly high frequency of UVB-S in human beings, including black-skinned persons, implies that the trait is not perceived by evolutionary processes as deleterious. The possible selective advantages conferred by alleles that determine UVB-S are discussed with respect to cutaneous infections in which mortality and morbidity are primarily mediated by immunopathogenic processes.

One-year monkey heart xenograft survival in cyclosporine-treated baboons. Suppression of the xenoantibody response with total-lymphoid irradiation

The shortage of cadaveric human organs for transplantation could be alleviated by the use of xenografts. Long-term (> one-year) survival of xenografts in humans or experimental animals has not been achieved with previous immunosuppressive protocols. Poor results in xenotransplantation compared with allotransplantation have been attributed to a more potent antibody response rather than to cell-mediated responses. To investigate these issues a concordant heterotopic cardiac xenograft model was developed in conjunction with cyclosporine and/or total-lymphoid irradiation. Concordant models permit examination of xenoantigen induced antibody and cell-mediated responses since preformed humoral factors (in discordant models) do not cause hyperacute rejection. Four groups of baboon recipients received cervical heart transplants from cynomolgous monkeys. Group I (n = 2), untreated, mean survival (MS) = 6 days; group II (n = 5), CsA and methylprednisolone, MS = 25 days; group III (n = 3), preoperative TLI, MS = 29 days; group IV (n = 6), preoperative TLI and CsA+MP, MS = 255 days (> 77, > 108, > 142, 184, > 480, 540 days). Heart xenografts of CsA-MP-treated recipients appear to be destroyed predominantly by antibody (IgM)-mediated processes whereas cell-mediated rejection is likely the major reaction in TLI-treated recipients. CsA-MP-treated recipients had early immunohistochemical evidence of antibody and complement-mediated rejection (deposition of IgM and complement but not IgG on heart xenografts). In contrast IgM and complement deposits were not detected on heart xenografts in TLI- and TLI-CsA-treated recipients. IgG xenoantibodies were only detected on the two rejected heart grafts of TLI-CsA-treated recipients. CsA-MP-treated recipients rapidly developed high xenoantibody titers (1:256 to 1:512) that immediately preceded rejection. In contrast, TLI-treated animals developed lower levels of xenoantibody (< or = 1:8) and TLI-CsA-treated recipients had no detectable xenoantibody during the initial three months after transplantation (and titers no greater than 1:8 thereafter.) The lack of xenoantibody was likely not due to a generalized inhibitory effect of the immunosuppressants on B cell function since all classes of serum immunoglobulins were in the normal range. Intragraft cytolytic lymphocyte activity was detected in rejecting TLI- and TLI-CsA-treated recipients but could not be detected in xenografts of CsA-MP-treated recipients. One explanation for these data is that TLI (either directly or indirectly) induces a state of specific B cell unresponsiveness to monkey xenoantigens, thereby preventing IgM mediated rejection in the third week after transplantation.(ABSTRACT TRUNCATED AT 400 WORDS)

Enhanced spontaneous and induced LAK function in baboons receiving total lymphoid irradiation (TLI)

TLI has potent immunosuppressive effects, but there is concern over its possible carcinogenic properties. The aim of the study was to assess to what degree TLI may compromise natural killer (NK) and lymphokine activated killer (LAK) cell function. There was a significant increase (P less than 0.0001) in both NK-cell function (measured against K562 targets) and spontaneous LAK-cell function (measured against DAUDI targets) in fresh blood lymphocytes throughout a course of 8 x 100 cGy fractionated TLI. This may be related to a three- and sevenfold increase, respectively, in CD16+ CD8- and CD56+ CD2- cell frequencies over the same period. Mitogen-induced interleukin 2 (IL-2) synthesis from blood lymphocytes was inhibited by up to 75% with as little as 100 cGy of TLI. Expression of IL-2 receptors on fresh lymphocytes did not vary and remained low. Therefore spontaneous LAK occurrence appeared to be triggered through an IL-2-independent pathway. The in vitro addition of IL-2 verified that cells retained their ability to respond to this lymphokine resulting in greatly enhanced induced LAK function. This was most probably mediated by CD56+ cells which were found to readily express IL-2 receptors upon mitogen stimulation. In conclusion, fractionated low-dose TLI appears to enhance MHC unrestricted immune surveillance in a manner independent of IL-2 production.

[A histochemical analysis of the reactions of the lymphoid organs and liver in a radiation lesion (experimental research)]

A histochemical study is presented of the functional state of the lymphoid organs and liver of guinea pigs under the effect of small and large doses of roentgen rays. Changes were found in the quantitative content of nucleic acids and lipofuscin already several days after irradiation accompanied by structural-qualitative reorganization of cells.

The effects of thymomodulin and thymolymphotropin on the stress response of neuroendocrine system by gamma-irradiated Wistar rat

Thymomodulin and Thymolymphotropin, biologically active thymus derivative peptides exert recovery effects on the functionality of some membrane bound, mitochondrial and lysosomal enzymes (monoamine oxidase, ATPase, phosphatases, cytochrome oxidase, succinate oxidase) affected by gamma-irradiation. These drugs exert antistress effect by re-establishing the function of hypothalamus-pituitary-adrenal axis and that of lymphoid organs.

Systemic administration of recombinant interleukin-6 in mice induces proliferation of lymphoid cells in vivo

Interleukin-6 (IL-6) is a pleiotropic cytokine and has been shown to support the growth of T and B lymphocytes in the presence of mitogens in vitro. IL-6 can induce human natural killer (NK) and interleukin-2 (IL-2)-induced lymphokine-activated killer cell (LAK) activity in vitro. It can also mediate antitumor effects in various murine models. In order to understand the mechanism of in vivo action, we have investigated the proliferation of lymphoid cells in vivo and the effects on NK, and LAK cell activities in response to IL-6 administration in mice. In vivo proliferation was measured by labeling the DNA of dividing cells with [125I]iodo-2'-deoxyuridine. C57BL/6 mice were injected ip with either IL-6 or HBSS control two times a day for 3 days and in vivo proliferation was measured. For comparative purpose IL-2 was administered and in vivo effects were analyzed. IL-6 caused significant proliferation of cells mainly in the spleen, while, IL-2 caused proliferation in the lungs, liver, spleen, and kidneys. Pretreatment irradiation (500 rad) of mice abrogated the IL-6-induced proliferation indicating radiosensitive cells are involved. Furthermore, in vivo proliferation was not observed in young nude mice treated with IL-6. To investigate whether the proliferating cells were cytotoxic, we tested for LAK (vs. fresh MCA-102 tumor targets) and NK (vs. Yac-1 tumor targets) activities in the organs of mice treated with IL-6 or IL-2 by 4 h 51Cr-release assay. IL-2 administration induced the generation of LAK activity and increased NK cytotoxicity in various organs, but IL-6 had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective radiation of hematolymphoid tissue delivered by anti-CD45 antibody

The ability to deliver radiation selectively to lymphohematopoietic tissues may have utility in conditions treated by myeloablative regimens followed by bone marrow transplantation. Since the CD45 antigen is the most broadly expressed of hematopoietic antigens, we examined the biodistribution of radiolabeled anti-CD45 monoclonal antibodies in normal mice. Trace 125I or 131I-labeled monoclonal antibodies 30G12 (rat IgG2a), 30F11 (rat IgG2b), and F(ab')2 fragments of 30F11 were injected i.v. at doses of 5 to 1000 micrograms. For both intact antibodies, a higher percentage of injected dose/g (% ID/g tissue) in blood was achieved with higher antibody doses. However, as the dose of antibody was increased, the % ID/g in the target organs of spleen, marrow, and lymph nodes decreased. At doses between 5 and 10-micrograms, % ID/g in these tissues exceeded that in lung, the normal organ with the highest concentration of radiolabel. In contrast, thymus was the only hematopoietic organ in which the % ID/g increased with increasing antibody dose, although at high dose the % ID/g was still far below that achieved in the other hematopoietic organs. Antibody 30F11 F(ab')2 fragments were cleared more quickly than intact antibody from blood and from both target and nontarget organs, although the relationship between increasing antibody dose and decreasing % ID/g in spleen, marrow, and lymph nodes was observed. The time-activity curves for each dose of antibody were used to calculate estimates of radiation absorbed dose to each organ. At the 10-micrograms dose of 30G12, the spleen was estimated to receive a radiation dose that was 13 times more than lung, the lymph nodes 3 to 4 times more, and the bone marrow 3 times more than lung. For each antibody fragment dose, the radiation absorbed dose per MBq 131I administered was lower because the residence times of the fragments were shorter than those of the intact antibody. Thus these estimates suggested that the best "therapeutic ratio" of radiation delivered to target organ as compared to lung was achieved with lower doses of intact antibody. We have demonstrated that radiolabeled anti-CD45 monoclonal antibodies can deliver radiation to lymphohematopoietic tissues with relative selectivity and that the relative uptake and retention in different hematolymphoid tissues change with increasing antibody dose.

The development of a posttransplant TLI treatment strategy that promotes organ allograft acceptance without chronic immunosuppression

The effectiveness of fractionated TLI in promoting allograft tolerance without chronic drug therapy is well established experimentally. TLI has not been widely applied in clinical transplantation, largely due to logistic and medical limitations of pretransplant TLI conditioning. Potential use of posttransplant TLI (PT-TLI) has not been critically evaluated. In this study we investigated PT-TLI in combination with rabbit antithymocyte globulin (RATG) in the absence of chronic immunosuppressive drugs as a strategy for inducing long-term kidney allograft acceptance. Recipients were studied with and without infusion of DR-CD3- donor bone marrow cells (DBMC). Normal rhesus monkeys, which received no pretransplant treatment, underwent bilateral intrinsic nephrectomy and splenectomy at the time of transplantation. RATG was administered daily for 3-5 consecutive days beginning on day 0. A total dose of 500-625 cGy of fractionated TLI was given in 4-5 treatments at 125 cGy per day beginning on day +1. Whereas neither PT-TLI nor RATG monotherapy induced long-term graft acceptance in splenectomized recipients, the combination of these modalities was remarkable in promoting long-term allograft acceptance without immunosuppressive drug therapy. Of 4 recipients given RATG x 5, splenectomy and PT-TLI, all were free of acute rejection. Of these, 3/4 had graft survivals greater than 100 days, 2/4 were greater than 150 days and 1/4 greater than 365 days. Of 5 recipients given this treatment plus an infusion of DR-CD3-DBMC, 4/5 grafts survived greater than 150 days and 3/5 still have normal functioning grafts at greater than 365 days. PT-TLI accentuated and prolonged changes in PBL subpopulations that were initially affected by RATG. Depressed levels of CD3+ cells were present for 4-5 months, with large numbers of circulating CD4+CD3- and especially CD8+ CD3- cells. In addition, antibody responses to RATG and alloantigens were suppressed in PT-TLI-treated recipients. Overall, the combination of PT-TLI, splenectomy, and RATG was found to be effective in promoting long-term allograft acceptance without chronic immunosuppressive drug therapy. The infusion of DR-CD3- DBMC in recipients treated with PT-TLI, RATG and splenectomy appeared to further increase the incidence of stable long-term survivors. If infectious complications can be improved, this approach may provide a clinically applicable posttransplant treatment strategy for inducing functional allograft tolerance.

Blocking of mixed lymphocyte reaction by spleen cells from total lymphoid-irradiated mice involves interruption of the IL-2 pathway

Treatment with total lymphoid irradiation (TLI) before organ transplantation results in high incidences of donor-specific tolerance. However, the exact mechanism of how TLI induces or maintains tolerance is not known. In many experimental systems of tolerance, lack of IL-2 plays a central role in tolerance induction, as stimulation of immunocompetent cells with Ag in an insufficient IL-2 environment results in tolerance. To examine whether tolerance induction by TLI might involve the IL-2 pathway, we examined how TLI cells affect the ability of immunocompetent cells to produce IL-2 and express IL-2R in the MLR. Responder cells from MLR cultures in which cells from TLI-treated mice were added proliferated 50 to 70% less and produced 68 to 94% less IL-2 bioactivity than responder cells from control cultures. However, coculture of TLI cells into MLR did not alter IL-2R expression on responder cells, as measured by two-color FACS analysis. We found no evidence that TLI cells deleted MLR responder cells. Interestingly, exogenous IL-2 did not restore proliferation of MLR responder cells. These results suggest that TLI may induce tolerance by interrupting the IL-2 pathway in immunocompetent cells. Moreover, that exogenous IL-2 failed to restore immunocompetence suggests that tolerance in the TLI model may be easy to induce and very stable, and provides a rationale for the higher incidences of donor-specific tolerance after TLI treatment.

Prolongation of xenograft survival after combination therapy with 15-deoxyspergualin and total-lymphoid irradiation in the hamster-to-rat cardiac xenograft model

Adequate immunosuppression remains a major obstacle to successful xenotransplantation, with early xenograft rejection appearing to be mediated by humoral factors. Total-lymphoid irradiation (TLI) and 15-deoxyspergualin (DOSP) have been shown to be effective immunosuppressive agents in allografs. In this study, TLI alone and in combination with DOSP and cyclosporine were evaluated in the hamster-to-rat heterotopic cardiac xenograft model. The animals were divided into four groups: group 1--control (n = 9); group 2--TLI alone, administered pretransplant at 125 cGy/day, four days per week, for three weeks (n = 12); group 3--TLI plus CsA at 10 mg/kg/day (n = 17); and group 4--TLI plus DOSP at 2.5 mg/kg/day (n = 10). Tissue sections were taken from rejected xenografts in all treatment groups for histological examination. Complement-dependent cytotoxicity assays were performed on the control group and also the TLI-DOSP group. The control animals were found to have a mean graft survival of 3.2 +/- 0.4 days. TLI alone (5.8 +/- 0.7 days) did not significantly improve graft survival in comparison with the control group. Combination of TLI with DOSP (26.3 +/- 5.9 days) results in significantly improved survival (P less than 0.05) in comparison with the control, TLI alone, and combination of TLI and CsA (13.6 +/- 8.6 days). Complement-dependent cytotoxicity assays revealed that control groups have low rat antihamster lymphocytotoxic antibody titer (1/1-1/10) prior to xenografting, and that these antibody titers show a precipitous rise to a level of 1/640-1/1280 by day 3, the time at which rejection occurred. This correlates with the histological findings of the rejected hearts showing a severe humoral type of rejection and no evidence of cellular rejection. In contrast, animals in the TLI-DOSP group had markedly lowered rat antihamster lymphocytotoxic antibody titers (1/20-1/40) on day 3, and these titers only increased to 1/160 at time of rejection. This correlates with the histological findings of a lesser degree of humoral rejection in the TLI-DOSP group. Combination therapy with TLI and DOSP results in a marked increase of survival in xenografts in this model not seen with any other drug combination studied in over 500 xenografts in our laboratory. This study indicates that TLI combined with DOSP results in prolonged suppression of the antixenograft antibody response. This combination of agents appears to have the potential to prevent early xenograft rejection.

Alternative approaches for the induction of transplantation tolerance

The immunosuppressive drugs currently in use in clinical transplantation are undoubtedly very effective at controlling graft rejection. However, their use is associated with a large number of side-effects, both immunological and non-immunological, particularly in the longer term. From an immunological point of view, the major disadvantage of these agents is that their mode of action is immunologically non-specific, resulting in blanket or pan-immunosuppression of the recipient's immune system. Thus, not only is the recipient's immune response against the organ graft suppressed, but responses to all other antigenic stimuli such as viral infections are also prevented. The transplant recipient can therefore become severely immunocompromised as a result of the drug therapy and is susceptible to opportunistic infections and an increased incidence of cancer. One of the aims for the design of new immunosuppressive therapy is to develop protocols that are both effective and immunologically specific, such that only the immune response to the transplanted organ is suppressed. The optimal approach would be to induce tolerance to the donor histocompatibility antigens before transplantation, permanently paralysing the ability of the recipient's immune system to mount a rejection response against the graft. Some of the approaches for the induction of immunological tolerance currently being explored in clinical transplantation will be discussed. These include total lymphoid irradiation (TLI) and donor bone marrow transfusion combined with anti-lymphocyte globulin (ALG) post-transplantation. In addition some new approaches for the induction of tolerance before transplantation currently being investigated in experimental systems will be presented.

A subset of asialo GM1+ cells play a protective role in the occurrence of graft-versus-host disease in mice

In three different murine models of bone marrow (BM) transplantation the capacity of asialo GM1+ cells to suppress graft-vs-host disease (GVHD) was investigated. In a first model, total lymphoid irradiation (TLI)-treated BALB/C mice were given 1 mg of anti-asialo GM1 antibody. This led to the disappearance of functional suppressor cells after TLI. Injections of anti-asialo GM1 into TLI-treated BALB/C mice before infusion of 30 x 10(6) fully allogeneic (C3H) BM cells, led to a significantly decreased survival rate as compared to TLI-treated mice injected with control serum before BM transplantation (survival 29 and 83%, respectively, at 120 days after transplantation, p = 0.0032 log rank). The mortality of the former group was due to GVHD as 1 degree all dying animals showed clinical and histologic signs of GVHD, 2 degrees all animals were chimeric and 3 degrees mice receiving no or syngeneic BALB/C BM had excellent survival rates excluding BM aplasia or increased susceptibility for infections as reason for the mortality of the allogeneic BM recipients. In a second model, asialo GM1+ cells were removed in vitro from the C3H BM inoculum before injection into lethally irradiated (9 Gy) BALB/C recipients. In mice kept in specific pathogen-free conditions, this procedure resulted into a significant mortality (12/12) as compared to mice receiving BM pretreated with control serum (1/12, p = 0.0001 log rank). When kept in conventional housing, GVHD occurred in both groups but much earlier in the group receiving anti-asialo GM1-treated BM (median survival time 6 vs 46 days for the control mice, p = 0.001 log rank). No animal receiving anti-asialo GM1 and treated with syngeneic BM died, thus excluding toxicity, increased susceptibility to infections, or decreased graft take as a cause of mortality. In a last model, asialo GM1 cells were removed from syngeneic BM in a BM transplantation model in which T cell-depleted syngeneic (BALB/C) and non-T cell-depleted allogeneic (C3H) BM was administered to lethally irradiated (9 Gy) BALB/C mice. Also in this model GVHD-related mortality only occurred in the group of mice receiving syngeneic BM from which asialo GM+ cells were depleted before infusion (3/12). Our experiments thus clearly show that asialo GM1+ cells from both recipient (the TLI model) as well as donor origin (the TBI experiments) can suppress the occurrence of GVHD.

Spontaneous and cytokine-inducible 'natural' immunoglobulin secreting cells in organized lymphoid tissues of mice

The number and frequency of spontaneous and cytokine-inducible 'natural' immunoglobulin-secreting cells (ISC) were determined in bone marrow (BM), spleen and Peyer's patch (PP), in vitro. Cells were cultured at limiting dilution in the presence or absence of exogenous recombinant cytokines and supernatants then assayed for total immunoglobulin (Ig) and Ig isotype using an ELISA. Most spontaneous ISC were found in the spleen and BM, with fewer in PP. The addition of recombinant interleukin 5 (rIL-5) promoted a marked increase in both the ISC frequency and the amount of Ig secreted/ISC whereas recombinant IL-6 (rIL-6) promoted only a marginal increase. Recombinant IL-4 (rIL-4) promoted a marginal increase in ISC frequency only. The isotype profile of ISC was in the order IgM greater than IgG2 greater than IgA greater than IgG3 greater than IgG1. The exposure of cells to 1200 rad of gamma-radiation resulted in decreased numbers of spontaneous ISC in all tissues, but the addition of rIL-5 or rIL-6 to the irradiated cells increased both the ISC frequency and Ig secreted. The Ig isotype profile was similar to that of non-irradiated ISC with a few minor exceptions. This large population of potential cytokine-inducible ISC could contribute to 'natural' Ig secretion in vivo.

The analysis of the defense mechanism against indigenous bacterial translocation in X-irradiated mice

The defense mechanism against indigenous bacterial translocation was studied using a model of endogenous infection in X-irradiated mice. All mice irradiated with 9 Gy died from day 8 to day 15 after irradiation. The death of mice was observed in parallel with the appearance of bacteria from day 7 in various organs, and the causative agent was identified to be Escherichia coli, an indigenous bacterium translocating from the intestine. Decrease in the number of blood leukocytes, peritoneal cells and lymphocytes in Peyer's patches or mesenteric lymph nodes was observed as early as 1 day after irradiation with 6 or 9 Gy. The mitogenic response of lymphocytes from various lymphoid tissues was severely affected as well. The impairment of these parameters for host defense reached the peak 3 days after irradiation and there was no recovery. However, in vivo bactericidal activity of Kupffer cells in mice irradiated with 9 Gy was maintained in a normal level for a longer period. It was suggested that Kupffer cells play an important role in the defense against indigenous bacteria translocating from the intestine in mice.

Total lymphoid irradiation to prevent graft rejection in recipients of HLA non-identical T cell-depleted allogeneic marrow

Patients who undergo transplantation with genotypically non-identical T cell-depleted bone marrow are at high risk of graft failure. We have previously shown that graft failure in this setting is an active immunologic process in which CD3+ CD8+ host T cells specifically cytotoxic for donor hematopoietic cells mediate rejection of the graft. In order to reduce the incidence of graft rejection in these patients, we conducted a pilot trial of total lymphoid irradiation (TLI) as an adjunct to total body irradiation (TBI) in an attempt to suppress the activity of residual host derived alloreactive lymphocytes capable of mediating rejection. Ten adults (ages 17-42 years) with hematologic malignancies were treated with TLI prior to hospitalization for allogeneic bone marrow transplantation (BMT). The BMT preparative regimen consisted of cyclophosphamide (60 mg/kg x 2) followed by TBI. The majority of patients received 750 cGy TLI delivered to two complementary radiation ports in five equal 150 cGy fractions. Nine of 10 recipients of genotypically non-identical CD6-depleted marrow who were pre-treated with TLI experienced full hematologic engraftment compared with none of four similar patients previously transplanted without TLI (p = 0.001). TLI induced significant lymphopenia in patients prior to marrow infusion, but had no suppressive effects on the reconstitution of donor lymphocytes. TLI, in combination with T cell depletion of donor marrow, may decrease the rate of graft rejection in individuals who lack perfectly matched HLA-identical sibling donors.

Mechanisms of immune injury in rheumatoid arthritis: evidence for the involvement of T cells and heat-shock protein

Evidence for the involvement of T cells, especially CD4+ T cells, in the pathogenesis of RA is substantial and includes 1) the correlation between prolonged CD4+ T-cell depletion and improvement in joint disease in the absence of observable changes in the levels of autoantibodies (rheumatoid factors) in the blood and joints, 2) the infiltration of the inflamed synovial tissues with T cells and, 3) the increased susceptibility of individuals to RA with certain HLA-DR haplotypes. The most direct evidence for the involvement of CD4+ T cells is provided by recent studies which demonstrate rapid improvement in the joint disease manifestations of RA following the infusion of anti-CD4 monoclonal antibodies (Herzog et al. 1989, Walker et al. 1989). It is unlikely that T cells alone are responsible for the joint injury in RA. Autoantibodies (rheumatoid factors) in the joint which contribute to the release of complement breakdown products, and to the secretion of cytokines such as IL-1 by macrophages must also play an important role. Indeed, depletion of CD4+ cells after TLI or therapy with monoclonal antibody reduces, but does not eliminate, joint disease activity. The residual joint disease activity is probably influenced by the continued contribution of autoantibodies to joint injury. Production of these autoantibodies may not be dependent on help from CD4+ cells, since little change is observed in autoantibody levels after CD4+ cell depletion. The mechanisms by which T cells mediate to the joint disease in RA are not clear. Little or no direct evidence of cytotoxic effects of T cells on autologous joint cells has been reported. Considerable evidence suggests that at least some T-cell cytokines (i.e., TNF alpha, IL-6) can contribute to the proliferation of synovial lining cells which results in the marked build-up of inflammatory tissue (pannus) in the joints of patients with RA (Firestein et al. 1990). In addition, T cells may recruit other joint cells, such as macrophages, to secrete cytokines (i.e., IL-1) which both contribute to synovial cell proliferation, and cartilage and bone degeneration. The marked reduction in the spontaneous secretion of IL-1 by synovial biopsies, and improvement in disease activity after TLI support this notion. Interestingly, the CD4+ T-cell lymphokines, IL-2 and IFN-gamma, were not spontaneously secreted in detectable quantities by synovial biopsies. This suggests that the pattern of lymphokines secreted by T cells in the joint in RA are not typical of that in delayed-type hypersensitivity reactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of cyclosporine A and methylprednisolone on the graft-versus-leukemia effects across major histocompatibility barriers in mice following allogeneic bone marrow transplantation

The effect of post-transplant immunosuppressive agents used in anti-GVHD prophylaxis on leukemic relapse was tested using a murine model of originally spontaneous, subsequently transplantable and non-immunogenic B cell leukemia (BCL1). (BALB/c x C57BL/6)F1 mice inoculated with 10(7) BCL1 cells were conditioned by total lymphoid irradiation (TLI) (1600 cGy), cyclophosphamide (200 mg/kg) or total body irradiation (TBI) 750 cGy and reconstituted with C57BL/6 (C57) bone marrow cells (30 x 10(6] or 10 x 10(6) bone marrow cells with additional 2 x 10(6) donor-type spleen cells, respectively. Mice were treated by cyclosporine A (CSA) 20 mg/kg i.p., or methylprednisolone (MP) 10 mg/kg i.p. for 10 days each and one group of controls received no post-transplant therapy. Stable chimerism was documented in all recipients with greater than or equal to 90% donor-type C57 cells in the peripheral blood. Eighty-nine percent of the mice treated by CSA following conditioning with TLI developed leukemia within 70 days, whereas none of the MP-treated mice and none of untreated chimeras showed any evidence of leukemia for more than 150 days. Adoptive transfer experiments using 10(5) spleen cells obtained from recipients conditioned with TBI were done to monitor residual leukemic cells following different post-transplant treatments. Eight-five percent of recipients of spleen cells obtained from mice treated with CSA developed leukemia in contrast with 33% and 25% when spleen cells were obtained from mice treated with MP or untreated controls, respectively (p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Canine pancreas and kidney transplantation following total-lymphoid irradiation

The effect of total-lymphoid irradiation on survival of canine pancreas and kidney allografts was studied. TLI had a marked immunosuppressive effect as measured by in vitro immune responses and reduced circulating leukocytes. Despite the changes, median graft survival times for animals treated with 800 cGy (9 days) or 1800 cGy (9.5 days) were not significantly different from untreated control animals (7 days). The addition of low-dose antithymocyte globulin (10 mg/kg/day) on post-transplant days 0, 2, 4, 6, 8, and 10 had no measurable synergistic effect. Similarly, median segmental pancreas allograft survival times after 1700-2200 cGy of TLI treatment (16.5 days) were only marginally longer than those of untreated controls (9 days). The only animal to maintain a graft for greater than 200 days was matched to the donor in mixed lymphocyte culture (MLC). This animal was able to reject a third-party skin graft after 8 days while a graft from the original donor was still surviving after 21 days when the pancreas graft failed from a chronic-type rejection. These results indicate that TLI alone or in combination with ATG will not be predictably effective as a method of prolonging allograft survival. The role of matching major histocompatibility complex antigens in TLI treatment requires clarification.

Total lymphoid irradiation and antigen-specific tolerance: future therapy for experimental myasthenia gravis?

Total lymphoid irradiation (TLI) is effective in the immunosuppressive treatment of human and experimental autoimmune disorders, including experimental autoimmune myasthenia gravis (EAMG). Under certain circumstances. TLI may facilitate the induction of specific tolerance to antigens present during or shortly after the TLI treatment. This study was designed to determine whether TLI could induce or enhance tolerance to acetylcholine receptor (AChR), the antigen in myasthenia gravis, or to other antigens. We presented the antigens in various potentially tolerogenic forms to rats that were first pre-treated with TLI, or controls treated with sham irradiation. Injection of deaggregated human gamma globulin (HGG), a classical tolerogen, was most effective; it produced antigen-specific tolerance, which was significantly enhanced by pre-treatment with TLI. Injection of HGG coupled to rat peritoneal cells induced a moderate degree of specific tolerance; in this case, pre-treatment with TLI added only nonspecific suppression. In contrast, AChR, either in solubilized form with no adjuvant, or coupled to syngeneic rat peritoneal cells, failed to induce tolerance, and actually primed the immune system, when given alone or in conjunction with TLI. Subsequent challenge with AChR resulted in an enhanced (secondary) anti-AChR antibody response. These results show that the nature of the antigen itself may predispose to tolerance or to immune stimulation. AChR appears to be highly immunogenic. However, if a tolerogenic fragment or form of AChR can be identified, its use in combination with TLI may result in specific tolerance. If such specific tolerance can be induced during an ongoing autoimmune reaction to AChR, it would be an effective treatment for myasthenia gravis.

Effects of thymus irradiation on the immune competence of T cells after total-lymphoid irradiation

Spleen cells from mice receiving TLI, with or without thymus shielding, were investigated for in vitro and in vivo defects. At 4-6 weeks after irradiation spleen cells of both groups showed a normal number of Thy1 (T cells), L3T4 (CD4 positive T cells) cells, and an absence of natural suppressor cells. Splenocytes of the nonthymic shielded TLI group were not able to mount either a normal in vitro response (in MLR or PHA) or an in vivo graft-versus-host-disease reaction when injected into lethally irradiated adult allogeneic recipients or into neonatal F1 hybrids. This was in contrast to the normal immune capacity of spleen cells from the thymus shielded group that gave normal MLR and PHA tests in vitro and provoked GVHD in vivo. Thymuses recovered from mice receiving TLI with or without thymic shielding were however equally efficient in restoring the immune capacity after transplantation into neonatally thymectomized mice as measured by the PHA assay. Thymic irradiation is therefore necessary but not sufficient for creating long-lasting immune defects after TLI.

[Characteristics of the radiation-induced changes in the content of sterols and squalene in the lymphoid system tissues and erythrocyte membranes of rats]

Ionizing radiation causes considerable changes in the content of sterols and squalene in the lymphoid system tissues and erythrocyte membranes which is in accordance with the concept of high radiosensitivity of haemopoietic tissue. The processes of cholesterol conversion to its oxy-derivatives are increased under the effect of radiation. The content of some lipid components in the lymphoid system tissues and erythrocyte membranes is changed depending on the dose and time after irradiation. There is a relationship between the changes in the sterol composition and in the properties of erythrocyte membranes.

Treatment with total lymphoid irradiation, cyclosporin A and a monoclonal anti-T-cell antibody in a hamster-to-rat heart transplantation model: graft survival and morphological analysis

Treatment with preoperative total lymphoid irradiation and post-transplant cyclosporin A has been shown to have a synergistic effect on graft survival in allo- and xenotransplantation. Specific monoclonal antibodies against T cells and T cell subpopulations could offer new ways of preventing graft rejection in xenotransplantation. Graft survival and histology were examined after total lymphoid irradiation plus cyclosporin A treatment versus cyclosporin A plus a monoclonal antibody in a concordant, heterotopic, hamster-to-rat heart transplantation model. Preoperative total lymphoid irradiation was given at a dose of 1.25 Gy, 12 times over a period of 3 weeks. Cyclosporin A at a dose of 12.5 mg/kg per day was administered perorally and OX-19, a pan T cell monoclonal antibody, was given as intraperitoneal injections at doses of 100 micrograms or 500 micrograms/kg per day from day 0 until graft rejection. While total lymphoid irradiation alone prolonged graft survival to 9.4 days, total lymphoid irradiation plus cyclosporin A extended graft survival to a mean of 22 days. Cyclosporin alone or combined with the monoclonal antibody could not increase graft survival significantly when compared to untreated animals, which rejected their grafts within 3.7 days. Vascular rejection was the characteristic morphological finding, even after some weeks of excellent graft function. In conclusion, total lymphoid irradiation and cyclosporin A had a synergistic effect on graft survival in this concordant xenotransplantation model, although recent impressive results from other groups could not be reproduced. Total lymphoid irradiation combined with cyclosporin A appears to delay a primary humoral graft rejection, while the mechanism of rejection, judged by histology, stays the same.

Deficits in T helper cells after total lymphoid irradiation (TLI): reduced IL-2 secretion and normal IL-2 receptor expression in the mixed leukocyte reaction (MLR)

Spleen cells from BALB/c mice treated with total lymphoid irradiation (TLI) and from normal, unirradiated mice were compared in the mixed leukocyte reaction (MLR). Although the percentage of CD4+ cells in the spleen was close to normal, 4 to 6 weeks after TLI, the MLR of unfractionated spleen cells from irradiated mice was more than 10-fold lower than controls. A similar reduction was observed when purified CD4+ cells were used as responders in the MLR. Secretion of IL-2 by cells from irradiated mice was also about 10-fold lower than controls. However, the percentage of CD4+ and CD8+ cells which expressed IL-2 surface receptors during the MLR was similar using spleen cells from irradiated and control mice. Addition of an exogenous source of IL-2 restored the proliferative capacity of the irradiated cells and suggests that the lack of IL-2 secretion is the likely explanation of the marked deficit in the MLR of CD4+ spleen cells after TLI.

Significant prolongation of hamster liver transplant survival in Lewis rats by total-lymphoid irradiation, cyclosporine, and splenectomy

The effects of total lymphoid irradiation, cyclosporine and splenectomy alone and in combination have been studied in liver transplants from the LVG hamster to the LEW rat. Neither CsA alone, splenectomy alone, nor TLI alone prolonged graft survival. CsA/splenectomy and TLI/CsA produced significant prolongation of graft survival. TLI/CsA/splenectomy prolonged graft survival by over sixfold compared with controls. While CsA alone was ineffective in reducing lymphocytotoxic antidonor antibody, splenectomy alone or CsA/splenectomy did significantly suppress production of antibody. Only very low levels of antibody could be detected in animals treated with TLI/CsA/splenectomy. TLI/CsA/splenectomy has an immunosuppressive effect sufficient to significantly prolong liver graft survival in the LVG hamster to LEW rat combination and may represent a promising treatment protocol in experimental cross-species transplantation.