Specific immunosuppression by local lymphoid irradiation using subcutaneous injection of palladium-109 labeled allogeneic lymphocytes

We have previously shown that intravenously administered palladium-109 labeled lymphocytes (Pd-L) migrated specifically to peripheral lymphoid organs where they caused selective lymphoid irradiation resulting in significantly prolonged cardiac allograft survival. This study evaluates the biodistribution of subcutaneously injected allogeneic Pd-L and the capacity of such labeled cells carrying a large dose of irradiation at a local site to attract and subsequently delete alloreactive T lymphocytes. It was hypothesized that subcutaneously administered allogeneic lymphocytes labeled with a large dose of palladium-109 will attract and then kill by irradiation the host effector cells which might permit prolongation of donor-specific allograft via partial clonal deletion. The results showed that 80% (injected dose) of subcutaneously injected allogeneic Pd-L remained at the site of administration while 20% of injected dose/gram was localized in the ipsilateral popliteal lymph node. No significant radioactivity was found in the other lymphoid and nonlymphoid organs. Pd-L effectively deleted the donor-specific effector cells, as measured by specific unresponsiveness to donor lymphocytes in mixed lymphocyte reaction. Donor cardiac allograft survival, however, was not prolonged over that found in naive recipient controls, although it was significantly prolonged when compared to cardiac allograft survival in controls sensitized by identical injections of unmodified subcutaneous allogeneic lymphocytes (mean survival time +/- SD of 6.5 +/- 0.8 vs. 3.0 +/- 0.6 days). These results suggest that partial clonal deletion of specific alloreactive cells achieved by this approach alone is insufficient to induce unresponsiveness to allografts in vivo.

Evidence for mouse Th1- and Th2-like helper T cells in vivo. Selective reduction of Th1-like cells after total lymphoid irradiation

Purified CD4+ BALB/c spleen T cells obtained 4-6 wk after total lymphoid irradiation (TLI) helped normal syngeneic B cells to produce a vigorous antibody response to TNP keyhole limpet hemocyanin in adoptive cell transfer experiments. However, the same cells failed to transfer delayed-type hypersensitivity to the adoptive hosts as measured by a foot pad swelling assay. In addition, purified CD4+ cells from TLI-treated mice were unable to induce graft vs. host disease in lethally irradiated allogeneic C57BL/Ka recipient mice. In response to mitogen stimulation, unfractionated spleen cells obtained from TLI mice secreted normal levels of IL-4 and IL-5, but markedly reduced levels of IL-2 and INF-gamma. A total of 229 CD4+ clones from spleen cells of both normal and TLI-treated mice were established, and the cytokine secretion pattern from each clone was analyzed. The results demonstrate that the ratio of Th1- and Th2-like clones in the spleens of normal BALB/c mice is 1:0.6, whereas the ratio in TLI mice is approximately 1:7. These results suggest that Th2-like cells recover rapidly (at approximately 4-6 wk) after TLI treatment and account for the early return of antibody helper activity and secretion of IL-4 and IL-5, but Th1-like cells recover more slowly (in approximately 3 mo) after irradiation, and this accounts for the deficit in cell-mediated immunity and the reduced amount of IL-2 and IFN-gamma secretion.

Total lymphoid irradiation reduces IgG autoantibody production and enhances specific antibody responses in NZB/NZW F1 mice

Thymus-independent primary antibody responses were studied in young and old (9 months) untreated and TLI-treated NZB/NZW and BALB/c mice. Untreated old NZB/NZW mice had a low primary response to Brucella abortus (BA) as compared to that of young NZB/NZW and BALB/c mice. However, TLI treatment resulted in a 130-fold increase in the IgG anti-BA primary antibody response at day 21 postimmunization, achieving similar levels to those of young NZB/NZW or nonautoimmune BALB/c mice. Anti-TNP responses to trinitrophenylated BA or Ficoll were masked by high background levels of anti-TNP antibodies. Despite the increase in the anti-BA response, spontaneous immunoglobulin secretion and autoantibody levels were markedly decreased after TLI in old NZB/NZW mice.

M cells and granular mononuclear cells in Peyer's patch domes of mice depleted of their lymphocytes by total lymphoid irradiation

The cytoarchitecture of Peyer's patches that were depleted of their lymphocytes by total lymphoid irradiation (TLI) was examined with particular attention to the effects on M cells in the follicle epithelium and on mononuclear cells in follicle domes underlying the epithelium. Five-month-old, specific pathogen-free Balb/c mice were irradiated with 200-250 rad/day, five times a week to a total dose of 3400-4250, and their Peyer's patches were either fixed for electron microscopy or frozen for immunohistochemistry 1-4 days after completion of irradiation. Control mice were examined at the same time intervals. Follicle domes of TLI mice had approximately one fourth the epithelial surface area of domes of control mice. Within the epithelium, lymphoid cells were virtually depleted after TLI, and yet the epithelium contained M cells. In control mice, most M cells were accompanied by lymphoid cells in invaginations of the apical-lateral cell membrane. In TLI mice, most M cells did not have such apical-lateral invaginations and were columnar shaped. Other than lacking lymphocytes, these cells appeared to be mature M cells. Some M cells did have lymphoid cells or granular mononuclear cells below their basal membranes, adjacent to the basal lamina. Below the epithelium, the proportion of granular mononuclear cells was greatly increased following TLI. The retention of M cells and the increase in proportion of granular mononuclear cells in follicle domes are consistent with selective depletion of lymphocytes following TLI. Persistence of M cells without lymphocytic invaginations after TLI suggests that M cells can differentiate in the absence of, or at least in the presence of very few, lymphocytes, and that invagination by lymphocytes is not necessary to maintain mature M cell morphology.

Failure to detect immune deficiency in rats after prenatal or early postnatal irradiation

We have looked for medium-term sequelae in the immune system of rats that had been X-irradiated (0-2 Gy whole-body irradiation) during prenatal or early postnatal life. At an age of 8 weeks the histology of the spleen was normal, and so was the distribution of B and T lymphocytes. The serum immunoglobulin levels were not significantly altered, even when the different isotypes were considered. At an age of 10 weeks, the rats were immunized with a T-dependent or a T-independent dinitrophenylated-carrier antigen. Normal levels of specific antibodies were generated in all groups of animals injected with the T-independent antigen. The T-dependent response, in contrast, was higher in animals irradiated between day 6 and day 20 of gestation (but not in rats irradiated early after birth). This increase, however, was significant only for the IgM and IgG1 responses of some irradiated groups. Thus no medium-term immunodeficiency could be documented with the methods used. The alteration in a T-dependent response, however, points to a radiosensitive T regulatory mechanism.

Inhibition of animal models of autoimmune disease and the induction of non-specific suppressor cells by SK&F 105685 and related azaspiranes

SK&F 105685 (N,N-dimethyl-8,8-dipropyl-2-azaspiro[4.5]decane-2-propanamine+ ++ dihydrochloride), administered orally to adjuvant arthritic (AA) rats inhibited immune-mediated hindpaw inflammation with an ED50 of 20 mg/kg/day. Both prophylactic and therapeutic administration were effective in this model. In addition, SK&F 105685 inhibited skin wheal responses to purified protein derivative (PPD) of tuberculin in AA rats and the development of hindleg paralysis associated with experimental allergic encephalomyelitis (EAE). Spleens of normal rats treated with SK&F 105685 were found to contain a population(s) of suppressor cells (SC) which inhibited the response of normal cells to Concanavalin A (Con A) in co-culture assays. The association between SC induction and anti-arthritic activity was determined by evaluating a series of chemically related azaspiranes in the AA rat model and for SC induction in normal rats. A statistically significant correlation was demonstrated (r = 0.79, P less than 0.001), indicating that SC induction may be responsible for the therapeutic activity of these compounds.

Use of cyclophosphamide and total lymphoid irradiation combined with cyclosporine in bone marrow transplantation for transfused severe aplastic anemia

Between February 1984 and August 1987, 10 patients with severe aplastic anemia were treated with bone marrow transplantation from HLA-identical sibling donors after preparation with cyclophosphamide (CY) 200 mg/kg and total lymphoid irradiation (TLI) 750 cGy. Ages ranged from 5 to 28 years (median 14 years). All patients were previously transfused. Median number of transfusions was 16 (range, 3-886). For post-transplant immunosuppression all patients were given cyclosporine and the last three patients received additional immunosuppression with short-term methotrexate. All patients had initial engraftment and survived for more than 3-46 months after transplantation. One patient developed significant acute graft-versus-host disease (GVHD) and three of nine recipients who survived more than 100 days developed chronic GVHD. One male patient who had received 21 transfusions from his marrow donor before transplantation suffered from persistent granulocytopenia. Otherwise all have Karnofsky performance scores of 90-100%. Although the number of patients is small, it appears that allogeneic bone marrow transplantation with the regimen of CY + TLI for preparation combined with cyclosporine (+ short-term methotrexate) for post-transplant immunosuppression is a promising modality for treatment of previously transfused patients with severe aplastic anemia.

Effect of total lymphoid irradiation on functional status in chronic multiple sclerosis: importance of lymphopenia early after treatment--the pros

To determine whether immunosuppression by total lymphoid irradiation (TLI) slowed deterioration of chronic progressive multiple sclerosis (MS), functional impairment score and blood lymphocyte counts were compared at 6-month intervals through 4 years following treatment of MS patients by either TLI (n = 27) or sham irradiation (n = 21). At each interval, 20 to 30% fewer TLI-treated patients had deteriorated (p less than 0.05 at 6, 12, and 18 months), and the difference in mean functional impairment score between groups became progressively greater (p less than 0.01 at 42 and 48 months). Benefit accrued principally to the 17 TLI-treated patients with absolute blood lymphocyte counts less than 900/mm3 3 months after treatment, whose mean functional impairment score remained within 0.6 units of baseline (p = NS), whereas the ten TLI patients with higher post-treatment lymphocyte counts had progressive deterioration (p less than 0.05 to p less than 0.001 versus TLI-treated patients with lower lymphocyte counts at all intervals except 30 months) and had deteriorated by more than 5 functional scale units by 42 and 48 months. Side effects were minor and complications rare in TLI-treated patients, but one TLI-treated patient developed staphylococcal sepsis. Thus, TLI slows deterioration of chronic progressive MS, with what appears to be enduring benefit through 4 years compartmented to patients with greater induced lymphopenia. Modification of lymphoid irradiation regimens to increase the proportion of MS patients who achieve a favorable degree of lymphopenia and to avert functional hyposplenism may further improve the benefit/risk ratio.

Clinical drawbacks of total lymphoid irradiation: the cons

Success has been reported with use of total lymphoid irradiation (TLI) in organ transplant recipients and in patients with rheumatoid arthritis and other autoimmune diseases. In a well-conducted randomized double blind clinical trial, Cook et al have found that TLI was superior to sham irradiation of patients with multiple sclerosis (MS). However, it is clear from looking at this data that not all patients responded to TLI and that with time disease activity returned. Our own experience with TLI in two MS patients was very disappointing. Despite its apparent benefit in some conditions, considerable drawbacks are associated with TLI. These include high financial cost, unpleasant treatment-related side effects, and the possibility that more serious morbidity as well as mortality may be treatment-related. Furthermore, the optimum therapeutic regimen for TLI has not yet been established. Issues related to cumulative dose, dose per fraction, frequency of fractions, field of irradiation, and interaction with other therapies still need clarification. For these reasons we do not recommend TLI as a treatment for MS.

Treatment of experimental myasthenia gravis with total lymphoid irradiation

Total lymphoid irradiation (TLI) has been reported to be effective in the immunosuppressive treatment of certain human and experimental autoimmune disorders. We have investigated the effects of TLI in Lewis rats with experimental autoimmune myasthenia gravis (EAMG) produced by immunization with purified torpedo acetylcholine receptor (AChR). The radiation is given in 17 divided fractions of 200 rad each, and nonlymphoid tissues are protected by lead shielding. This technique suppresses the immune system, while minimizing side effects, and permits the repopulation of the immune system by the patient's own bone marrow cells. Our results show that TLI treatment completely prevented the primary antibody response to immunization with torpedo AChR, it rapidly abolished the ongoing antibody response in established EAMG, and it suppressed the secondary (anamnestic) response to a boost of AChR. No EAMG animals died during TLI treatment, compared with six control animals that died of EAMG. TLI produces powerful and prompt immunosuppression and may eventually prove useful in the treatment of refractory human myasthenia gravis.

Immunosuppression prior to marrow transplantation for sensitized aplastic anemia patients: comparison of TLI with TBI

From May 1980 through July 1986, 26 patients with severe aplastic anemia, sensitized with multiple transfusions of blood products, were treated on either of two immunosuppressive regimens in preparation for bone marrow transplantation from a matched donor. There were 10 patients treated with total body irradiation (TBI), 200 cGy/fraction X 4 daily fractions (800 cGy total dose), followed by cyclophosphamide, 60 mg/kg/d X 2 d. An additional 16 patients were treated with total lymphoid irradiation (TLI) [or, if they were infants, a modified TLI or thoracoabdominal irradiation (TAI)], 100 cGy/fraction, 3 fractions/d X 2 d (600 cGy total dose), followed by cyclophosphamide, 40 mg/kg/d X 4 d. The extent of immunosuppression was similar in both groups as measured by peripheral blood lymphocyte depression at the completion of the course of irradiation (5% of initial concentration for TBI and 24% for TLI), neutrophil engraftment (10/10 for TBI and 15/16 for TLI), and time to neutrophil engraftment (median of 22 d for TBI and 17 d for TLI). Marrow and peripheral blood cytogenetic analysis for assessment of percent donor cells was also compared in those patients in whom it was available. 2/2 patients studied with TBI had 100% donor cells, whereas 6/11 with TLI had 100% donor cells. Of the five who did not, three were stable mixed chimeras with greater than or equal to 70% donor cells, one became a mixed chimera with about 50% donor cells, but became aplastic again after Cyclosporine A cessation 5 mo post-transplant, and the fifth reverted to all host cells by d. 18 post-transplant. Overall actuarial survival at 2 years was 56% in the TLI group compared with 30% in the TBI group although this was not statistically significant. No survival decrement has been seen after 2 years in either group. There was less long-term morbidity in the TLI group compared with TBI although the numbers of surviving patients are small. With no difference in engraftment or survival, it is suggested that, for sensitized severe aplastic anemia patients, who are to receive a non-T cell-depleted marrow from a matched donor, prudent cytoreduction should include a fractionated, moderate dose irradiation regimen with maximum organ sparing, that is either TLI or TAI.

Ocular toxoplasmosis in immunosuppressed nonhuman primates

To investigate the role of cellular immunodeficiency in recurrent toxoplasmic retinochoroiditis, six Cynomolgus monkeys (Macaca fascicularis) with healed toxoplasmic lesions of the retina were immunosuppressed by total lymphoid irradiation. Three months prior to irradiation 30,000 Toxoplasma gondii organisms of the Beverley strain had been inoculated onto the macula of eye in each monkey via a pars plana approach. Toxoplasmic retinochoroiditis developed in each animal, and lesions were allowed to heal without treatment. During total lymphoid irradiation animals received 2000 centigrays (cGy) over a 7-week period. Irradiation resulted in an immediate drop in total lymphocyte counts and decreased ability to stimulate lymphocytes by phytohemagglutinin. Weekly ophthalmoscopic examinations following irradiation failed to show evidence of recurrent ocular disease despite persistent immunodeficiency. Four months after irradiation live organisms were reinoculated onto the nasal retina of the same eye in each animal. Retinochoroidal lesions identical to those seen in primary disease developed in five of six animals. Toxoplasma organisms therefore were able to proliferate in ocular tissue following the administration of immunosuppressive therapy. This study fails to support the hypothesis that cellular immunodeficiency alone will initiate recurrent toxoplasmic retinochoroiditis. Results suggest that reactivation of disease from encysted organisms involves factors other than suppression of Toxoplasma proliferation. If reactivation occurs by other mechanisms, however, cellular immunodeficiency then may allow development of extensive disease.

Treatment. Disease-modifying therapies

Many patients with systemic lupus can be treated effectively with antimalarials and nonsteroidal anti-inflammatory drugs without ever having to take systemic corticosteroids at all or for any significant length of time. On the other hand, some patients with life-threatening disease, active major organ disease, or intolerable corticosteroid toxicities should be given immunosuppressive drugs, plasmapheresis, and/or other therapies in addition to corticosteroids early in their disease course, before permanent, end-organ damage occurs and before the predictable serious and debilitating toxicities of prolonged, daily high-dose corticosteroids develop. Just as lupus patients now routinely undergo detailed serologic testing, it is conceivable that, in the future, routine determination of human leukocyte antigen (HLA) haplotypes45 and T-cell subsets88a will help define, at disease onset, those patients who are destined to have severe disease. Perhaps this knowledge, combined with a better understanding of the exact mechanisms of action of these disease-modifying therapies, will allow a more rational approach to the treatment of SLE.

Clinical and immunological studies of cadaveric renal transplant recipients given total-lymphoid irradiation and maintained on low-dose prednisone

Twenty-five recipients of cadaveric renal transplants were given total lymphoid irradiation (TLI), perioperative antithymocyte globulin, and low-dose prednisone as the sole maintenance immunosuppressive drug. Nine patients were diabetic, and follow-up was between 19 and 37 months. One-year graft and patient survival was 76% and 87%, respectively, Serious complications included four deaths from cardiovascular disorders, and two deaths from viral infections. Studies of peripheral blood T cell subsets showed a prolonged reduction in the absolute number of helper (Leu-3+) cells, and a rapid recovery of cytotoxic/suppressor (Leu-2+) cells. Analysis of the latter subset, using the monoclonal antibody 9.3, showed that the ratio of suppressor/cytotoxic cells was approximately 10:1. The normal ratio is 1:1. The mean mixed leukocyte reaction remained below 30% of the pre-TLI value for 6 months, and approached 80% at two years. Similar kinetics were observed in the proliferative response to mitogens. The results show that maintenance immunosuppressive drug therapy can be reduced after TLI as compared with conventional drug regimens that use prednisone in combination with cyclosporine and/or azathioprine.

[Effect of prolonged continuous external irradiation on humoral immunity indices of mice]

Changes in the content and function of cell populations and subpopulations involved in the humoral response of mice to the thymus-dependent antigen were investigated. The effect was followed during a prolonged continuous exposure to 137Cs gamma-emitter (total dose--5 Gy and daily dose--12 cGy for 22 hours) and after its termination. The data obtained give evidence for a decrease of the pool of polypotent lymphocyte precursors (CFUs), stable moderate hypoplasia of central and peripheral organs of the immune system, distinct inhibition of antibody production at the expense of reduced activity of precursors of lymphocytes, B-lymphocytes and T-helpers. In the remote postirradiation period residual radiation damage was seen in polypotent and committed precursors of lymphocytes and T-helpers which was responsible for the trend towards the decline of antibody production, hypoplasia in the spleen and lymph nodes being persistent.

The effects of gamma irradiation on the lymphoid organs of rainbow trout and subsequent susceptibility to fish pathogens

Fish were irradiated with 60Co gamma rays at doses ranging from 10 to 50 Gy. Lethal doses were determined in fishes of different ages. For a given dose, fry and fingerlings were more susceptible than subadults. Whatever the irradiation dose was, the fish displayed a sharp decrease in blood leucocyte count. At the lowest doses, this acute leucopaenia was reversible. The cellular damage in the lymphoid organs was particularly obvious in the thymus. The depletion of lymphoid cells from immunocompetent organs decreased (viral hemorrhagic septicaemia, VHS) or increased (Y. ruckeri, A salmonicida) the susceptibility of trout to pathogens. The suppressive effect of radiation was age dependent. Irradiation appeared to be a reliable technique to detect asymptomatic carrier fish.

Old mice recover the ability to produce IgG and high-avidity antibody following irradiation with partial bone marrow shielding

The splenic plaque-forming-cell (PFC) response to trinitrophenylated bovine gamma globulin of 18- to 20-month-old mice is markedly depressed, with a preferential loss of indirect (IgG) PFC and high-avidity-antibody-secreting cells compared to 6- to 8-week-old animals. The anti-trinitrophenyl response of old mice, whose peripheral lymphoid system has been reconstituted from their own bone marrow after irradiation while their bone marrow was partially shielded, includes high-avidity and IgG PFCs relatively comparable to those of normal young mice. If young mice are irradiated while their bone marrow is partially shielded and given purified splenic T cells from either old or young donors during recovery from irradiation, then the avidity distribution and the ratio of IgG/IgM PFCs they produce in response to trinitrophenylated bovine gamma globulin reflects the characteristic immune response of the T-cell donor. These results are consistent with the hypothesis that the bone marrows of old and young mice are similar with regard to the spectrum of B-cell clones that they can generate and that it is peripheral regulatory effectors that are responsible for much of the age-related change in the immune response. In addition, if one calculates the PFC avidity distribution taking into account those cells whose secretion of antibody was inhibited by anti-idiotype autoantibodies, then it is clear that there are more high-avidity B cells present in old mice than are detected by the conventional plaque-inhibition assay. Thus, the reduced avidity of the PFC response of old mice appears to be, at least in part, due to down regulation by anti-idiotype autoantibodies.

Dissection of the mechanisms of immune injury in rheumatoid arthritis, using total lymphoid irradiation

Eleven patients with intractable rheumatoid arthritis were treated with total lymphoid irradiation. After radiotherapy, there was a marked decrease in the number and function of peripheral blood helper/inducer (Leu-3+) T lymphocytes, in the spontaneous secretion of interleukin-1 by synovial biopsy specimens, and in the activity of the joint disease. In contrast, levels of IgM, IgA, and IgG rheumatoid factors and C3 concentrations in blood and synovial fluid samples did not change significantly after therapy with total lymphoid irradiation.

Radiation therapy of spontaneous autoimmunity: a review of mouse models

The classical types of generalized autoimmune disease in man are systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Several murine strains which develop SLE and sometimes RA-like diseases are now available. They should help in the understanding of the etiopathology of SLE and RA. Basically two main therapeutic strategies which use solely irradiation have been tried; one being sublethal whole-body irradiation (WBI) and the other fractionated total lymphoid irradiation (TLI). Other protocols which combine lethal WBI and stem cell transplantation have often been attempted. It was regularly found that the bone marrow transplant (BMT) dictates the immune status of the recipient. This paper reviews the data published about NZB, NZB/W, BXSB and MRL mice in this context.

Therapeutic strategies in immunosuppression after renal transplantation

Immunosuppressive strategies are directed at both the prevention and treatment of rejection. Strategies to prevent rejection are based on cyclosporine, and aim to achieve improved graft survival while decreasing the incidence of nephrotoxicity, and include the use of low doses of cyclosporine, cyclosporine conversion protocols, triple therapy (with low doses of azathioprine, cyclosporine, and steroids), and delayed administration of cyclosporine. There is no agreement as to the most satisfactory protocol at this time, but the use of cyclosporine has allowed the use of low doses of steroids or even discontinuation of steroid therapy, a major advance in pediatric transplantation. The treatment of rejection still depends on the use of high doses of steroids, but heterologous anti-lymphocyte globulin and OKT3, a pan-T monoclonal antibody, can be used with success in steroid-resistant rejection episodes. Other monoclonal antibodies directed at leukocyte subpopulations are likely to be of value in time as our understanding of the mechanisms of rejection of renal allograft increases.

Total lymphoid irradiation in alloimmunity and autoimmunity

Total lymphoid irradiation has been used as an immunosuppressive regimen in autoimmune disease and organ transplantation. The rationale for its use originated from studies of patients with Hodgkin disease, in whom this radiotherapy regimen was noted to induce profound and long-lasting immune suppression and yet was well tolerated, with few long-term side effects. Total lymphoid irradiation is a unique immunosuppressive regimen that produces a selective (and long-lasting) reduction in the number and function of helper T cells and certain subsets of B cells. Conventional immunosuppressive drugs show little selectivity, and their effects are short-lived. The most important aspect of total lymphoid irradiation is the potential for achieving transplantation tolerance and permanent remissions in autoimmune disease in laboratory animals. Attempts are being made to achieve similar goals in humans given total lymphoid irradiation, so that immunosuppressive drugs can be ultimately withdrawn from transplant recipients and patients with lupus nephritis.

T cell regulatory disturbances in the rheumatic diseases

Significant immunoregulatory abnormalities have been described in both SLE and RA. In SLE, deficient suppressor T cell activity may result from depletion of CD8+ suppressor precursors, depletion of CD4+ suppressor-inducer cells, or impaired lymphokine production and deficient CD4+ cell activation of suppression by CD4+ cells. The net result is an apparent failure to inhibit antibody synthesis. The defects in RA are less well defined, although in RA there also is evidence that either deficient suppression or deficient suppression-induction plays a role in the pathogenesis of disease. There is evidence for local lymphocyte activation in the synovium, with possibly impaired local immunoregulation. However, the precise nature of the immune reactions in the synovium and their relationship to systemic immunoregulatory abnormalities remain unclear.

Total lymphoid irradiation in multiple sclerosis: blood lymphocytes and clinical course

We have found a significant relationship between blood lymphocyte count and prognosis in 45 patients receiving either total lymphoid irradiation or sham irradiation for chronic progressive multiple sclerosis. Patients with sustained lymphocyte counts less than 900 mm-3 for prolonged periods after treatment showed less rapid progression over the ensuing 3 years than did patients with multiple sclerosis who had lymphocyte counts above this level (p less than 0.01). Our results suggest that a simple laboratory test, the absolute blood lymphocyte count, may serve as a valuable barometer for monitoring the amount of immunosuppressive therapy needed to prevent progression in patients with multiple sclerosis, and possibly other autoimmune diseases.

2,000-centiGray total lymphoid irradiation for refractory rheumatoid arthritis

Because toxicity with the use of 3,000 centiGray (cGy) of total lymphoid irradiation (TLI) was observed in an earlier study, 2,000-cGy treatments were delivered in a 2-portal format to 7 patients and in a modified 3-portal fashion to 6 patients, as part of a randomized, investigator-blinded trial of TLI treatment for refractory rheumatoid arthritis. Analysis of combined data from the 13 patients revealed statistically significant improvement in 5 clinical indicators of disease activity at the end of TLI and 6 and 12 months later, accompanied by T4-specific immunosuppression. Management considerations resulted in the introduction of prednisone therapy in 5 patients, methotrexate in 4, and azathioprine in 1 during the interval of 8-12 months post-TLI. Herpes zoster occurred in 5 patients prior to the initiation of this additional therapy. These data indicate that, in patients with rheumatoid arthritis, a TLI dose of 2,000 cGy is sufficient to produce measurable benefit that lasts for 6 months, and that the improvement can be maintained at 12 months by the use of prednisone and methotrexate.

[Interphase death of lymphoid cells: role in the genesis of radiation sickness and molecular mechanisms]

An analysis of the data on the effect of lymphoid cells on the proliferation and differentiation of hemopoietic stem cells has led to a conclusion that radiation injury of lymphocytes plays an important role in the pathogenesis of the cerebrospinal syndrome. The molecular mechanisms of lymphocyte interphase death were considered. It was shown that due to some peculiarities in the energy supply of these cells the appearance of breaks in DNA causes the development of biochemical processes resulting in a decrease in NAD, an increase in the activity of nucleases, a decrease in ATP, and the accumulation of active metabolites of glycolysis. These reactions result in an increase in the disintegration of DNA, chromatin and pyknosis of lymphocyte nuclei.

The influence of dose and dose rate of total lymphoid irradiation in the rat cardiac allograft model

Immunosuppression generated by total lymphoid irradiation (TLI) may be of use in solid organ transplantation. We have investigated the use of TLI in the rat cardiac allograft model. Lewis rats received TLI from a cobalt-60 machine. The daily dose was 1.25 Gy and treatments were administered 4 days per week. We performed experiments to assess the effect of dose rate upon graft survival. The dose rate was varied by changing the source to animal distance and by using a lead attenuator. Cardiac allografts from each ACI donor rat were transplanted to the recipient Lewis rat's abdomen utilizing microvascular surgical technique. Heart graft survival times (GST) were monitored by direct palpation of the cardiac impulse. Immune function was measured by an activity index of the mixed lymphocyte reaction. In the absence of any immunosuppression there was a mean GST of 6.9 +/- 0.3 days. When a graft was placed the day following completion of TLI, there was an increase in GST as the total TLI dose was increased. Mean GST (+/- S.E.) following 5, 10, and 15 Gy were 12.3 +/- 1.3, 14.5 +/- 1.3, and 25.5 +/- 1.1 days, respectively. Following 20 Gy, GST decreased because of irradiation induced pulmonary toxicity and host death. When 3.5 weeks were allowed to elapse between the completion of TLI and transplantation, GST were less than those seen with equivalent doses of TLI and early transplantation. Mean GST following 5, 10, and 15 Gy and a delayed transplant were 7.2 +/- 0.1, 10.7 +/- 1.2, and 19.0 +/- 3.5 days, respectively. We tested the effect of dose rate upon GST.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal transplant patients treated with total lymphoid irradiation show specific unresponsiveness to donor antigens the mixed leukocyte reaction (MLR)

A group of 25 cadaveric renal transplant recipients received total lymphoid irradiation (TLI) before transplantation, rabbit anti-thymocyte globulin on alternate days for 10 days after transplantation, and low dose prednisone (5 to 10 mg/day) as the sole maintenance immunosuppressive therapy. Allograft function and the mixed leukocyte reaction (MLR) were monitored serially. After 18 to 30 mo, nine patients were selected on the basis of a return of the MLR such that the mean stimulation index to a panel of normal stimulator cells was greater than or equal to 5, a stable serum creatinine level which was less than or equal to 2 mg/dl, and a history of no more than one rejection episode. The MLR of these patients' post-transplant peripheral blood mononuclear leukocytes (PBML) against cryopreserved donor cells was compared with that against cryopreserved normal third-party cells. In control experiments, the MLR of cryopreserved pre-TLI recipient PBML or fresh normal PBML were tested against the same panel of donor and third-party stimulator cells. Seven of the nine recipients showed a pattern of specific unresponsiveness to the donor cells more than 18 mo after transplantation. Preliminary attempts to identify antigen specific suppressor cells were unsuccessful. The pattern of unresponsiveness may indicate a state of specific immune tolerance to the allogeneic graft.

Application of irradiation as an immunosuppressive agent

The concept of using total lymphoid irradiation (TLI) for immunosuppression is based on the prolonged and profound immunosuppressive effects observed after TLI in the treatment of patients with Hodgkin's disease. Pre-operative TLI of allograft recipients has been shown to be immunosuppressive when used alone or together with chemical immunosuppression. Fractionated TLI and allogeneic bone marrow injections produce stable chimaerism without graft-versus-host disease in inbred mice, rats and mongrel dogs and transplantation tolerance of skin and cardiac grafts in rats. In the primate, TLI and bone marrow injection result in significant tolerance of liver and kidney allografts. In 1959 sublethal whole-body irradiation was used as an immunosuppressive agent for the first successful related-human renal allografts between non-identical twins. Despite the dangers of myelosuppression, recent clinical experience has shown TLI to be a useful immunosuppressant for organ transplantation, allowing decreased dosage of concomitant immunosuppressive drugs.

Immunological and clinical observations in diabetic kidney graft recipients pretreated with total-lymphoid irradiation

In a feasibility study, twenty patients with end-stage diabetic nephropathy were treated with fractionated total-lymphoid irradiation (TLI, mean dose 25 Gy), before transplantation of a first cadaveric kidney. During radiotherapy, only one patient had a serious side effect (bone marrow depression). After transplantation four patients died (one of a myocardial infarction, one of ketoacidosis, and two of infections occurring during treatment of rejection crises). One graft was lost because of chronic rejection. The other 15 patients have a functioning graft (mean follow-up 24 months) and receive low-dose prednisone alone (less than 10 mg/day, n = 11) or in conjunction with cyclosporine (n = 4) as maintenance immunosuppressive therapy. A favorable clinical outcome after TLI (no, or only one, steroid-sensitive rejection crisis) was significantly correlated with a high pre-TLI helper/suppressor lymphocyte ratio, a short interval between TLI and the time of transplantation, and the occurrence of functional suppressor cells early after TLI. The most striking immunological changes provoked by TLI consisted of a long-term depression of the mixed lymphocyte reaction and of the phytohemagglutinin, and Concanavalin A or pokeweed-mitogen-induced blastogenesis. A rapid and complete recovery of the natural killer cell activity was observed after TLI. A permanent inversion of the OKT4+ (T helper/inducer) over OKT8+ (T suppressor/cytotoxic) lymphocyte ratio was provoked by a decrease of the OTK4+ subpopulation, together with a supranormal recovery of the OKT8+ lymphocytes. A majority of the latter lymphocytes did also express the Leu 7 and the Leu 15 phenotype.

Comparative toxicity of total lymphoid irradiation and immunosuppressive drug treated patients with intractable rheumatoid arthritis

Outcomes were compared between consecutive patients who had received either total lymphoid irradiation (TLI) or immunosuppressant treatment for intractable rheumatoid arthritis (RA). There were 33 TLI and 32 immunosuppressive recipients; all patients had failed standard therapy. Average followup from the start of therapy was 2.7 years for TLI and 5.9 years for immunosuppressive recipients. Final disability levels were the same in both groups; mortality was equal in both groups as well. There were more hospitalizations for infections in the TLI group and the infecting organisms tended to be staphylococcus or gram negative organisms. Apart from infections, there were more adverse effects reported in the immunosuppressive therapy group.

Suppressor cells induced by total lymphoid irradiation affect proliferation and lymphokine production of murine T helper cell clones

A key response to antigen is the activation of helper T cells to release lymphokines which stimulate and effect the immune reaction. This T cell population can secrete many different factors with diverse, often multifunctional roles, such as amplifying T or B cell antigen responses or being effectors of cell mediated delayed type hypersensitivity. Among these lymphokines are gamma-interferon (gamma-IFN), interleukin-2 (IL-2), or T cell growth factor, and lymphotoxin (LT) which has cytotoxic activity against a variety of cells. Immune suppression in mice following total lymphoid irradiation (TLI) has been correlated with the presence in lympho-reticular tissues of an antigen non-specific, null suppressor cell. This study examined what effects radiation induced suppressor cells had upon the in vitro activation and lymphokine responses of the ovalbumin (OVA) specific T helper cell clone, 153E6, following antigen presentation. Splenocytes from TLI treated mice obtained early in the post-irradiation period exerted a pan-inhibitory effect upon OVA induced 153E6 proliferation and its concomitant release of gamma-IFN, LT, and IL-2. As the interval from irradiation increased, splenocytes from TLI treated mice showed persistent suppression of 153E6 proliferation and gamma-IFN release, but had rapidly diminishing effects on the T cell's capacity to produce LT and IL-2. These findings suggest that suppressor cells induced by TLI have a marked inhibitory effect in vivo upon T helper cell proliferative responses to antigen and the production of various T helper cell lymphokines necessary to mediate the immune response. Such processes could contribute to the immunosuppressive effects of extensive nodal irradiation.

The effect of ionizing radiation on lipid metabolism in lymphoid cells

Lipid metabolism was studied in lymphoid tissues of rats after whole body irradiation with doses producing damage of different degrees to lymphoid cells (4-10 Gy). The content of free cholesterol, cholesterol esters, and total phospholipids was determined in peripheral blood lymphocytes and thymocytes 1-2 h after exposure. Simultaneously, the rate of in vitro incorporation of 2 14C-acetate into total lipids, phospholipids, and cholesterol of lymphoid cells was estimated. It was shown that exposure of rats to ionizing radiation caused activation of lipogenesis. Cholesterol synthesis was activated after a dose of 4 Gy and decreased with increasing dose.