Tacrolimus in pediatric renal transplantation

Tacrolimus was used as the primary immunosuppressive agent in 69 pediatric renal transplantations between December 17, 1989, and June 30, 1995. Children undergoing concomitant or prior liver and/or intestinal transplantation were excluded from analysis. The mean recipient age was 10.3+/-5.0 years (range, 0.7-17.5 years). Seventeen (24.6%) children were undergoing retransplantation, and six (8.7%) had a panel reactive antibody level of 40% or higher. Thirty-nine (57%) cases were with cadaveric kidneys, and 30 (43%) were with living donors. The mean donor age was 28.0+/-14.7 years (range, 1.0-50.0 years), and the mean cold ischemia time for the cadaveric kidneys was 27.0+/-9.4 hr. The antigen match was 2.7+/-1.2, and the mismatch was 3.1+/-1.2. All patients received tacrolimus and steroids, without antibody induction, and 26% received azathioprine as well. The mean follow-up was 32+/-20 months. One- and 4-year actuarial patient survival rates were 100% and 95%. One- and 4-year actuarial graft survival rates were 99% and 85%. The mean serum creatinine level was 1.2+/-0.8 mg/dl, and the calculated creatinine clearance was 82+/-26 ml/min/1.73 m2. The mean tacrolimus dose was 0.22+/-0.14 mg/ kg/day, and the level was 9.5+/-4.8 ng/ml. The mean prednisone dose was 2.1+/-4.9 mg/day (0.07+/-0.17 mg/kg/day), and 73% of successfully transplanted children were off prednisone. Seventy-nine percent were not taking any antihypertensive medications. The mean serum cholesterol level was 158+/-54 mg/dl. The incidence of delayed graft function was 4.3%. The incidence of rejection was 49%, and the incidence of steroid-resistant rejection was 6%. The incidence of rejection decreased to 27% in the most recent 26 cases (January 1994 through June 1995). The incidence of new-onset diabetes was 10.1%; six of the seven affected children were able to be weaned off insulin. The incidence of cytomegalovirus disease was 13%, and that of posttransplant lymphoproliferative disorder was 10%; the incidence of posttransplant lymphoproliferative disorder in the last 40 transplants was 5% (two cases). All of the children who developed posttransplant lymphoproliferative disorder are alive and have functioning allografts. Based on this data, we believe that tacrolimus is a superior immunosuppressive agent in pediatric renal transplant patients, with excellent short- and medium-term patient and graft survival, an ability to withdraw steroids in the majority of patients, and, with more experience, a decreasing rate of rejection and viral complications.

Systemic administration of cellular interleukin-10 can exacerbate cardiac allograft rejection in mice

Cellular interleukin-10 (cIL-10) has been shown to inhibit cytokine production by T helper type 1 (Th1) cells by blocking antigen presenting cell function. This activity has suggested that IL-10 might be useful in the treatment of transplant rejection. Stimulatory effects of IL-10 however, have also been observed both on T and B cell differentiation. In this study, we examined the influence of recombinant (r) mouse (m) IL-10 on heterotopic vascularized heart allograft survival in the B10(H2b)-->C3H(H2k) strain combination that crosses both major histocompatibility complex (MHC) and non-MHC-histocompatibility antigen (non-MHC-HA) barriers. The influence of IL-10 was also examined in the B10.BR (H2k)--> C3H combination with disparity at only non-MHC-HA loci. Postoperative intraperitoneal administration of IL-10 (100 microg/d, days 0-6) significantly accelerated heart graft rejection both in the B10-->C3H (mean survival time [MST] 7.8+/-0.2 days; control MST 10.6+/-0.6 days; P<0.05) and the B10.BR-->C3H combination (MST 14.3+/-0.5 days; control MST 77.7+/-14.4 days). Ex vivo IL-10 perfusion of donor hearts for either 15 min or 2 hr did not affect subsequent graft survival. Immunologic monitoring of transplanted mice revealed that IL-10 treatment (100 microg/d, i.p., days 0-6) increased both the circulating complement-dependent cytotoxic (CDC) antibody titer and splenic anti-donor cytotoxic T lymphocyte (CTL) activity measured up to 3 weeks posttransplant. These findings indicate that post transplant systemic administration of cIL-10 can promote vascularized allograft rejection, and that this may reflect stimulation both of B and T cell alloimmune responses.

Urgent revascularization of liver allografts after early hepatic artery thrombosis

Between April 1993 and May 1995, 17 adult orthotopic liver transplant recipients were found to have early hepatic artery thrombosis (HAT) after a median of 7 postoperative days (mean, 11). The HAT was diagnosed in all cases by duplex ultrasound. Thrombectomy was performed with urgent revascularization (UR), using an interposition arterial graft procured from the cadaveric liver donor, and arterial patency was verified with intraoperative angiography. In seven cases, intra-arterial urokinase was administered after the thrombectomy. Fifteen (88%) of the livers remained arterialized throughout the follow-up period (median, 15 months); the remaining two patients developed recurrent HAT after 6 and 8 months. Although there was a high rate of subsequent complications, 11 (65%) of the patients are alive without retransplantation, with a mean follow-up of 17 months. Despite having a patent hepatic artery, the remaining six patients (35%) died from infectious complications that usually were present before the UR. Thus, UR effectively restored arterial inflow in 88% of the patients with early HAT. The ultimate outcome was determined mainly by the presence of intra-abdominal complications at the time of UR. In conclusion, UR, rather than retransplantation, should be considered the prime treatment option for patients who develop early posttransplant HAT.

"Suboptimal" kidney donors: the experience with tacrolimus-based immunosuppression

Female, pediatric, and older donors have been associated with inferior graft survival after renal transplantation. We analyzed these three subgroups in 397 patients receiving tacrolimus-based immunosuppression. There were no differences in recipient age, incidence of retransplantation, or percentage of sensitized patients. Female donors, compared with male donors, were associated with comparable 1- and 3-year patient survival rates (96% and 93% vs. 95% and 92%, respectively) and comparable 1- and 3-year graft survival rates (90% and 80% vs. 88% and 81%, respectively). Renal function was also similar. Recipients of pediatric en bloc kidneys, when compared with recipients of other cadaveric kidneys, also had comparable 1- and 3-year patient survival rates (94% and 94% vs. 95% and 91%, respectively) and comparable 1- and 3-year graft survival rates (84% and 84% vs. 89% and 79%, respectively). Renal function was better in recipients of en bloc kidneys, with a mean serum creatinine level of 1.4+/-1.8 mg/dl vs. 2.0+/-1.5 mg/dl (P=0.01). In contrast to the first two subgroups, donors over 60 years of age, when compared with donors under 60 years of age, were associated with worse 1- and 3-year patient survival rates (88% and 80% vs. 96% and 94%, respectively; P<0.03) and worse 1- and 3-year graft survival rates (74% and 62% vs. 91% and 83%, respectively; P<0.0001). Renal function was worse in the older donor group, with a serum creatinine level of 2.7+/-1.2 mg/ml vs. 1.9+/-1.5 mg/dl (P=0.01). We conclude that, under tacrolimus-based immunosuppression, kidneys from female or very young pediatric donors are not associated with adverse outcomes, whereas kidneys from donors over 60 years of age are associated with inferior outcomes.

Costimulatory molecule-deficient dendritic cell progenitors (MHC class II+, CD80dim, CD86-) prolong cardiac allograft survival in nonimmunosuppressed recipients

We have shown previously that granulocyte-macrophage colony-stimulating factor-stimulated mouse bone marrow-derived MHC class II+ dendritic cell (DC) progenitors that are deficient in cell surface expression of the costimulatory molecules B7-1 (CD80) and B7-2 (CD86) can induce alloantigen-specific T-cell anergy in vitro. To test the in vivo relevance of these findings, 2 x 10(6) B10 (H2b) mouse bone marrow-derived DC progenitors (NLDC 145+, MHC class II+, B7-1dim, B7-2-/dim) that induced T-cell hyporesponsiveness in vitro were injected systemically into normal C3H (H2k) recipients. Seven days later, the mice received heterotopic heart transplants from B10 donors. No immunosuppressive treatment was given. Median graft survival time was prolonged significantly from 9.5 to 22 days. Median graft survival time was also increased, although to a lesser extent (16.5 days), in mice that received third-party (BALB/c; H2d) DC progenitors. Ex vivo analysis of host T-cell responses to donor and third-party alloantigens 7 days after the injection of DC progenitors (the time of heart transplant) revealed minimal anti-donor mixed leukocyte reaction and cytotoxic T lymphocyte reactivity. These responses were reduced substantially compared with those of spleen cells from animals pretreated with "mature" granulocyte-macrophage colony-stimulating factor + interleukin-4-stimulated DC (MHC class IIbright, B7-1+, B7-2bright), many of which rejected their heart grafts in an accelerated fashion. Among the injected donor MHC class II+ DC progenitors that migrated to recipient secondary lymphoid tissue were cells that appeared to have up-regulated cell surface B7-1 and B7-2 molecule expression. This observation may explain, at least in part, the temporary or unstable nature of the hyporesponsiveness induced by the DC progenitors in nonimmunosuppressed recipients.

The Pittsburgh randomized trial of tacrolimus compared to cyclosporine for hepatic transplantation

BACKGROUND

Tacrolimus (formerly FK506) was first used clinically in 1989 to successfully replace cyclosporine in hepatic transplant recipients who were experiencing intractable rejection or as the baseline drug from the time of operation. After extensive pilot experience, an institutional review board-mandated clinical trial comparing cyclosporine with tacrolimus was performed.

STUDY DESIGN

From February 16, 1990 to December 26, 1991, 154 patients were recruited. The competing drugs were combined with equal induction doses of prednisone in both arms of the study for the first 81 patients and with subsequently higher doses of prednisone in the remaining 35 patients who received cyclosporine and were entered into the trial. Drug crossover was permitted for lack of efficacy or adverse events. End points were rejection confirmed by biopsy and treatment failure leading to retransplantation or death.

RESULTS

Seventy-nine patients were randomized to the tacrolimus arm and 75 to the cyclosporine arm during 1990 and 1991. All patients were available for follow-up throughout the trial, which terminated on May 30, 1995. The mean duration of follow-up was four years. Patients randomized to the tacrolimus arm were less likely to experience acute rejection than were those receiving cyclosporine, with 36.2 percent of the patients receiving tacrolimus and 16.8 percent of the patients receiving cyclosporine showing freedom from rejection at one year (p = 0.003, likelihood ratio test). Survival of patients over the course of the study was virtually the same in the two groups.

The two-way paradigm of transplantation immunology

The events following organ transplantation require a reciprocal cell interaction which includes both the conventional host-versus-graft reaction and a graft-versus-host component. With all successful transplantation, both graft and recipient become genetic composites. Where donors were available, chimerism has been confirmed in 30-year kidney-recipient survivors, as well as in several liver and lung recipients. A majority of liver recipients have been able to acquire an immunosuppressant-free state after 10-year survival. Animal models suggest that donor-derived cells may exert a tolerogenic effect.

The Pittsburgh randomized trial of tacrolimus compared to cyclosporine for hepatic transplantation

BACKGROUND

Tacrolimus (formerly FK506) was first used clinically in 1989 to successfully replace cyclosporine in hepatic transplant recipients who were experiencing intractable rejection or as the baseline drug from the time of operation. After extensive pilot experience, an institutional review board-mandated clinical trial comparing cyclosporine with tacrolimus was performed.

STUDY DESIGN

From February 16, 1990 to December 26, 1991, 154 patients were recruited. The competing drugs were combined with equal induction doses of prednisone in both arms of the study for the first 81 patients and with subsequently higher doses of prednisone in the remaining 35 patients who received cyclosporine and were entered into the trial. Drug crossover was permitted for lack of efficacy or adverse events. End points were rejection confirmed by biopsy and treatment failure leading to retransplantation or death.

RESULTS

Seventy-nine patients were randomized to the tacrolimus arm and 75 to the cyclosporine arm during 1990 and 1991. All patients were available for follow-up throughout the trial, which terminated on May 30, 1995. The mean duration of follow-up was four years. Patients randomized to the tacrolimus arm were less likely to experience acute rejection than were those receiving cyclosporine, with 36.2 percent of the patients receiving tacrolimus and 16.8 percent of the patients receiving cyclosporine showing freedom from rejection at one year (p = 0.003, likelihood ratio test). Survival of patients over the course of the study was virtually the same in the two groups.

Tacrolimus pretreatment attenuates preexisting xenospecific immunity and abrogates hyperacute rejection in a presensitized hamster to rat liver transplant model

In the hamster to rat liver transplant model, we determined the efficacy of tacrolimus in attenuating natural xenospecific humoral immunity and in abrogating the hyperacute liver rejection that is produced by presensitizing the Lewis rat recipient. Hamster livers, transplanted orthotopically into naive rats (controls), were rejected with animal death after 6.4.+/- 0.5 (SD) days. The infusion on (day -6) of 1.5 x 10(7) hamster hepatocytes, or of 1.5 x 10(8) nonparenchymal cells (NPC), resulted in hyperacute rejection and death in < or = 1.9 days. However, when the rats were pretreated with 1 mg/kg/day tacrolimus from days -6 to -1, survival of non-presensitized animals was prolonged to 25 +/- 20 days and that of recipients presensitized with hamster hepatocytes to 36 +/- l6 days or with NPC to 32 +/- 1.7 days. The tacrolimus pretreatment significantly reduced the hamster-specific complement-dependent cytotoxic antibodies response directed to liver NPC but not to lymph node cell targets. These observations suggest that the prolongation of survival by appropriately timed treatment with this T cell directed drug model is caused by the inhibition of humoral as well as cellular xenograft rejection.

Impact of donor MHC class I or class II antigen deficiency on first- and second-set rejection of mouse heart or liver allografts

The influence of donor major histocompatibility complex (MHC) class I- or class II-deficiency on the initiation of first- and second-set rejection of mouse heart and liver allografts was examined. C3H (H-2k) mice received heterotopic cardiac or orthotopic liver grafts from unmodified B10 (H-2b), B6 (H-2b), b2m (H-2b; class I deficient) or AB0 (H-2b; class II deficient) donors. Organ survival was also investigated in C3H recipients that had been presensitized by a normal B10 skin graft 2-3 weeks before heart or liver transplantation. The absence of cell surface MHC class I or class II resulted in significant prolongation of primary cardiac allograft survival. Three of seven (43%) MHC class I-deficient, and two of five (40%) class II-deficient heart grafts were accepted indefinitely (survival time > 100 days). Thus both MHC class I and class II molecules appear to be important for the elicitation of first-set rejection in the heart allograft model. All liver allografts survived > 100 days in normal recipients. In C3H recipients that had been presensitized by a B10 skin graft, however, both heart and liver grafts from AB0 (class II deficient) donors underwent accelerated rejection (median survival time [MST] 3 and 4 days, respectively). In contrast, liver grafts from class I-deficient mice (b2m) were still accepted indefinitely by B10 skin-presensitized C3H recipients, whereas class I-deficient hearts survived significantly longer than those from class II-deficient or normal donors. These data demonstrate that the expression of donor MHC class I, and not class II is crucial in initiating second-set organ allograft rejection. In vitro monitoring revealed that at the time of organ transplant, both splenocytes and serum of the skin-presensitized animals displayed high cytotoxicity against AB0 (class II-deficient) but not against b2m (class I-deficient) targets.

Time to detection of cytomegalovirus (CMV) DNA in blood leukocytes is a predictor for the development of CMV disease in CMV-seronegative recipients of allografts from CMV-seropositive donors following liver transplantation

In 35 cytomegalovirus (CMV)-seronegative recipients of livers from CMV-seropositive donors, 32 (91%) developed CMV infection and 24 of them (75%) experienced disease. Polymerase chain reaction for CMV DNA in leukocytes had the best positive and negative predictive values for the development of disease within 2 months from transplantation, and shell-vial or tube culture viremia was the best predictor thereafter. In patients who developed CMV disease, CMV DNA was first detected at 46 days (median; range, 13-128) after transplantation, significantly earlier than the 77 days (range, 46-174) for those who did not develop CMV disease (P = .02). By a semiquantitative method, the CMV DNA level in the first positive sample did not predict disease development. However, the maximum CMV DNA level during infection was significantly higher in patients who developed CMV disease. In CMV-seronegative recipients of livers from CMV-seropositive donors, the time to DNA positivity following transplantation may predict disease progression and be useful as a guide for the initiation of preemptive therapy.

Second-set rejection of mouse liver allografts is dependent on radiation-sensitive nonparenchymal cells of graft bone marrow origin

Livers are accepted spontaneously when transplanted orthotopically from B10 (H2b) or BALB/c (H2d) to C3H (H2k) mice without host immunosuppression. Presensitization to donor can, however, be induced by skin grafting two weeks prior to liver transplantation, resulting in second-set or "accelerated" liver graft rejection, within 4-5 days. In this study, the role of liver nonparenchymal cells (NPC) in second-set rejection was tested by donor whole-body irradiation and replacement of donor B10 liver NPC with those of either third-party (BALB/c) or recipient strain (C3H) bone marrow. Irradiation alone (9.5 Gy) of normal B10 donors before liver transplantation significantly prolonged graft survival in presensitized C3H recipients. Three months after bone marrow transplantation (BMT), chimeric livers expressing third-party or recipient haplotype, were transplanted orthotopically into unmodified C3H recipients. Graft survival was prolonged significantly compared with livers from normal or syngeneically reconstituted B10 donors. Prolonged survival of chimeric (BALB/c->B10) livers was also evident in C3H mice presensitized to alloantigens expressed on both the liver parenchymal (B10) and third-party NPC (BALB/c) by simultaneous grafting of skin from each donor strain. Determination of graft cytokine mRNA profiles 4 days posttransplant showed that replacement of donor with third-party or recipient strain BM-derived cells was associated with reduced expression of IL-2 and IFN-gamma mRNA compared with that in grafts from syngeneically reconstituted donors. IL-10 transcripts, however, were not significantly affected. The results are consistent with a key role of radiation-sensitive, donor-specific NPC of bone marrow origin in second-set liver rejection in presensitized hosts. In this process, competent donor-strain NPC appear to augment the activity of primed T cells responsible for the second-set rejection.