Improved results of living-related liver transplantation with routine application in a pediatric program.

Living related liver transplantation (LRT) was introduced as a response to the shortage of donor organs that has existed for small children. Results were promising in the initial experience, with a one-year patient survival of 80% and a graft survival of 75%. Since the completion of the protocol, LRT has been considered routinely in the management of children in our center. We present here our experience with 45 consecutive transplants in which LRT accounts for 40% of grafts with an overall patient survival of 90%. Between 4/91 and 4/92, 45 OLT were performed in 41 children. Median age was 2.7 years (3 months to 13 years) and weight was 10.4 kg (3.5-60 kg). Thirty-five were primary grafts, 10 were retransplants. One patient received 2 grafts in the orthotopic auxiliary position. Cholestatic disorders including biliary atresia accounted for 60%, metabolic diseases for 15%. Grafts were obtained from cadaver donors in 27/45 (60%) cases; reduction was required in 12/27 (44%). LRT was performed in 18 cases. Fifty-two percent of recipients of cadaver grafts were UNOS status 4, while 16% of LRT recipients met these criteria. Actual patient survival for cadaver grafts is 21/24 (88%) and graft survival is 20/27 (74%). Patient survival in 18 LRT was 94%. Two grafts were lost to arterial thrombosis for a graft survival of 83%. All donors have been discharged and are well. One patient, a teenager with fulminant hepatitis, was successfully transplanted with a left lobe from his father. This experience demonstrates the programmatic flexibility accorded by use of LRT. Since 40% of grafts were LRT, more livers were available for urgent use for patients who did not have a donor available, as reflected in the 73% incidence of cadaver recipients on status 3 or 4. Therefore, patients are more likely to receive a transplant at the optimal time. We are now prepared to offer LRT for fulminant hepatic failure since the benefit of graft availability appears to outweigh concerns about coerced donation. The successful treatment of a teenaged patient may herald extension of LRT to adults. We conclude that the use of LRT should be expanded.

Selective breeding of miniature swine leads to an increased rate of acceptance of MHC-identical, but not of class I-disparate, renal allografts.

Previous work from this laboratory demonstrated that tolerance to MHC-identical or class I-disparate renal allografts develops in approximately one third of miniature swine without exogenous immunosuppression. A back-cross study indicated that rejection of MHC-identical transplants due to minor Ag was controlled by one or possibly two non-MHC-linked, autosomal dominant Ir genes. According to this hypothesis, and assuming complete penetrance, graft acceptors would be homozygous recessive at the relevant Ir loci, as would their offspring. Alternatively, if the gene(s) were incompletely penetrant, then two acceptors could give rise to a rejector. However, a high rate of MHC-identical graft acceptance would still be expected in the offspring of acceptors even if the Ir gene(s) were incompletely penetrant. To test this hypothesis and to obtain a higher frequency of acceptor animals for studies of tolerance, a program of selective breeding of renal allograft acceptors was begun. In the present paper, we assess the effect of selective breeding on renal graft acceptance. The analysis indicates a marked increase in the rate of MHC-identical graft acceptance, from 27.3% (n = 24) for the earliest of the four chronologic subgroups assessed to 64.5% (n = 33) for the most recent subgroup (p less than 0.0001). Calculations of kinship revealed that the increased acceptance of MHC-identical grafts was not the result of differences between acceptors and rejectors in donor/recipient consanguinity. Class I-disparate grafts (n = 128) were similarly stratified chronologically and compared. Unlike MHC-identical grafts, the rate of acceptance of class I-disparate grafts has not changed over time. We conclude that rejector/acceptor status with respect to class I MHC incompatibility is determined by genetic factors in addition to those that control responses to minor antigen incompatibilities only.

The failure of skin grafting to break tolerance to class I-disparate renal allografts in miniature swine despite inducing marked antidonor cellular immunity.

Long-term specific tolerance to one haplotype class I plus minor antigen disparate renal allografts develops without exogenous immunosuppression in approximately 35% of miniature swine (n = 128). Previous studies have suggested that this phenomenon is related to limited class I-specific helper T cell activity as evidenced by the failure of antibody class switching in vivo and the ability of exogenous interleukin 2 to elicit antidonor responses in vitro. To determine whether tolerance could be broken by inducing antidonor reactivity with donor antigen and a source of T cell help, multiple skin grafts bearing donor class I plus third-party class II antigens were placed on tolerant animals. Skin grafts were placed at least 3 months after the kidney transplant, at which time all recipients had normal renal function as measured by blood urea nitrogen and serum creatinine. First-set rejection of skin grafts by SLAad and SLAdd hosts occurred in 11.8 +/- 1.1 days (mean +/- SEM, n = 6) and in 9.3 +/- 0.9 days (n = 4), respectively. Coincident with skin rejection, most animals developed a transient rise in BUN to 62 +/- 11 mg/dl (n = 10) and a similar rise in Cr to 4.9 +/- 1.2 mg/dl (n = 10), with normal levels returning in all animals within two weeks. Subsequent skin grafts with the same disparity did not undergo second-set rejection and did not induce BUN or Cr elevations. Prior to skin grafting, animals showed no antidonor activity in mixed lymphocyte reaction or cell-mediated lymphocytotoxicity assays. After two skin grafts, all animals developed donor-specific CML and secondary MLR responses, and additional skin grafts amplified this cellular immunity. Development of marked antidonor immunity without a break in tolerance suggested that either graft adaptation or local suppression might be involved in maintaining tolerance to class I MHC antigens. In preliminary studies, an immunized SLAad animal and an immunized SLAdd animal were retransplanted with kidneys MHC matched to their first allografts. In both cases, the second graft was accepted permanently without immunosuppression, suggesting that graft adaptation is not necessary for the maintenance of tolerance to renal allografts in miniature swine.

Transplantation in miniature swine: analysis of graft-infiltrating lymphocytes provides evidence for local suppression.

Previous studies from this laboratory have demonstrated that swine tolerant of class I disparate renal allografts show peripheral antidonor cellular reactivity which can be augmented by skin grafting. To assess the possibility of local suppression, cell-mediated lymphocytotoxicity of graft-infiltrating lymphocytes was compared to that of peripheral blood lymphocytes from three tolerant and four acutely rejecting recipients of class I--disparate renal allografts. Mixed lymphocyte cultures using peripheral blood lymphocytes or graft-infiltrating lymphocytes and an equal number of irradiated peripheral blood lymphocyte stimulators were incubated for 6 days and tested in a 6-hr 51Cr release assay. Graft-infiltrating lymphocytes from rejecting animals had potent antidonor cell-mediated lymphocytotoxic activity with or without in vitro stimulation. Anti-third-party reactivity was seen with appropriate stimulation, suggesting heterogeneity of graft-infiltrating lymphocyte cultures. Peripheral blood lymphocytes from rejectors generated donor-specific cell-mediated lymphocytotoxicity. Graft-infiltrating lymphocytes from tolerant animals generated no antidonor cell-mediated lymphocytotoxicity with or without in vitro stimulation, but generated an anti-third-party response. Peripheral blood lymphocytes from tolerant animals displayed both antidonor and anti-third-party reactivity with appropriate in vitro stimulation. These data support the hypothesis that local suppression may contribute significantly to maintenance of tolerance to class I disparate renal allografts in miniature swine.

Mechanism of tolerance following class I--disparate renal allografts in miniature swine. Cellular responses of tolerant animals.

Previous studies utilizing a recombinant MHC haplo-type in our partially inbred miniature swine herd have demonstrated that some recipients matched only for SLA class II show long-term acceptance of renal allografts without exogenous immunosuppression. Such animals have been shown to develop systemic tolerance as evidenced by prolonged rejection times of subsequent donor-specific, but not third-party, skin grafts. In the present studies in vitro cellular responses of long-term tolerant animals and of 7 animals studied sequentially are presented. Long-term tolerant animals demonstrated responses consistent with the absence of the class I reactive helper populations normally present in naive controls. Animals studied sequentially segregated into two groups based on cellular reactivity and survival. All animals showed complete loss of antidonor class I cell-mediated lymphocytolytic (CML) reactivity by postoperative day 10. However, animals surviving less than 20 days maintained CML reactivity to donor class I plus third-party class II in the posttransplant period, while animals surviving greater than 40 days lost such reactivity. Addition of exogenous interleukin 2 could not reverse this loss. These studies suggest that tolerance induction to a renal allograft across a class I only difference involves effects on both helper and killer class I reactive cell populations.