Results of positive cross-match transplantation in African American renal transplant recipients.

Positive cross-match (PXM) renal transplantation has been utilized to address the issue of the increasing demand for transplantation with the shortage of suitable organs. Our primary objective was to analyze the outcomes of African American (AA) PXM renal transplant recipients utilizing AA negative cross-match (NXM) renal transplant recipients as a comparator group. This was a retrospective study consisting of all PXM patients who underwent a desensitization protocol and all AA NXM transplant recipients at the University of Illinois at Chicago from July 2001 to March 2007. We found that AA PXM recipients had significantly lower estimated glomerular filtration rate (eGFR) at 1 year than AA NXM (46.2 vs. 60.6, p = 0.007). AA PXM who experienced acute rejection within the first year were more likely to have an eGFR less than 30 mL/min/1.73 m(2) at 1 year compared to their NXM counterparts (45.5% vs. 12.5%, p = 0.034). Positive cross-match renal transplantation in AA seems to be associated with a high degree of AR and severe renal compromise at 1 year. Larger studies are needed to determine if protocols that are associated with good short-term outcomes in non-AA need to be modified for the AA population.

Effect of robotic assistance on the "learning curve" for laparoscopic hand-assisted donor nephrectomy.

BACKGROUND: The number of living-related donor kidney transplantations have increased since the advent of minimally invasive surgery. Robotic technology has emerged as a promising alternative to laparoscopic techniques. The authors reviewed their institution experience with robotic hand-assisted donor nephrectomies (RHADNs). METHODS: Between August 2000 and April 2006, 273 robotically assisted left donor nephrectomies were performed using a hand-assisted technique. Prospectively collected information for 214 patients regarding complications, hospital stay, blood loss, warm ischemia time, operative time, and outcomes is presented. RESULTS: The cohort of donors included 110 men and 104 women with a mean age of 36 years (range, 18-61 years). These donors included 86 African Americans, 46 Caucasians, 74 Hispanics, and 8 of other races. Left renal artery anomalies were found in 61 patients (29%). Four patients underwent conversion to open surgery. The hospital stay was 2.3 days (range, 1-8 days), the blood loss 82 ml (range, 10-1,500 ml), and the mean warm ischemia time 98 s (range, 50-200 s). The operative time was 201 min (range, 100-320 min) for the first 74 cases, 129 min (range, 65-240 min) for the second 70 cases, and 103 min for the last 70 cases (p < 0.001), for an overall average of 150 min. Complications decreased significantly after the first 74 cases. The 1-year patient survival rate was 100%, and the 1-year graft survival rate was 98%. The average recipient creatinine at 6 months was 1.4 mg/dl. CONCLUSIONS: Specific changes in operative technique over time have improved patient safety and diminished complications with RHADN. Currently, RHADN can be performed expeditiously with a minimal rate of complications and conversion to open procedure by a surgical team with appropriate training and experience.

Early coronary calcification in children and young adults with end-stage renal disease.

Cardiovascular disease is a major cause of morbidity and mortality in children and young adults with end-stage renal disease. In our study, we retrospectively analyzed the records of 11 patients who had undergone electron beam computerized tomography in our dialysis unit. Our patients, aged 11 to 24 years (median, 19.3 years) were on dialysis or had functioning grafts. Coronary calcification was observed in seven patients (64%) with a mean calcium score of 273.8 +/- 708 (range 0.8 to 1864) in our study population. We compared clinical characteristics like age, gender, duration of end-stage renal disease, time on hemodialysis, body mass index, and blood pressures between the patients with calcifications (group I) and those with out calcification (group II). We also compared the laboratory data including daily calcium and calcitriol intake, lipid profile, serum calcium and phosphorus levels, calcium/phosphorus products, and serum parathyroid hormone levels in the both groups. The mean daily dose of total calcium, triglyceride level, and calcium/phosphorus products were higher in the calcification group though not statistically significant. The mean daily dose of calcitriol was significantly higher in patients with calcification. Using Spearman multivariate correlation, we found a correlation between the coronary calcium scores and mean daily doses of total calcium and calcitriol (r = .750, P =.008 and r = .869, P = .001, respectively). We conclude that coronary calcification, which is a proven predictor of cardiovascular disease, begins at a very early age and that daily doses of elemental calcium and calcitriol seem to be important factors in our study population.

Risk factors for wound healing complications in sirolimus-treated renal transplant recipients.

Impaired surgical site healing occurs in 20% to 50% of sirolimus (SRL)-treated renal transplant (RT) recipients, with most patients having received concomitant corticosteroids. We determined the incidence of surgical site complications among RT recipients receiving SRL with mycophenolate mofetil (MMF), with most patients on a steroid-avoidance protocol. SRL/MMF patients with complications within 3 months of transplantation were compared with 1) SRL/MMF patients without them and 2) matched RT recipients receiving tacrolimus (FK)/MMF. Between January 2002 and March 2005, 44 of 300 (15%) RT recipients received SRL within 6 weeks of transplantation. Fourteen (31.8%) developed lymphocele, bladder leak, wound dehiscence, cellulitis, or an abscess. Obesity (BMI > or =30 kg/m2) was significantly associated with problems: the mean BMI of SRL cases with complications was 29.9 kg/m2 vs 25.4 kg/m2 for SRL patients without them (P = .047). Seventy-one percent of obese SRL patients experienced complications compared with 24.3% (P = .025) of non-obese SRL patients. Surgical treatment was required in 29% of patients. Rates of maintenance steroid use were similar in SRL complicated cases compared with SRL patients without them. The FK control group showed a lower rate of complications (14.3%; P = .163) despite similar BMI, rejection rates, and chronic steroid use as the SRL group. Obesity and graft rejection were independent predictors of complications. Thus, among a group of predominantly steroid-free recipients on SRL, the rates of wound complications were similar to those seen previously, but the highest risk for them was observed in obese recipients and in those with acute rejection episodes. Wound complications were associated with significant morbidity.

Effect of race on the occurrence of posttransplant diabetes in kidney transplant recipients treated with early steroid discontinuation.

INTRODUCTION: Early steroid discontinuation (within 5 days after transplant) has been associated with a lower incidence of posttransplant diabetes mellitus (PTDM). A retrospective study was done to assess the incidence of PDTM in relation to racial groups in kidney transplant recipients who received early steroid discontinuation. METHODS: Between January 2002 and January 2004, 125 consecutive, primary adult kidney transplant recipients (51 cadaveric donor, 74 living donor) were performed at the University of Illinois at Chicago. The first 34 recipients were treated with steroid maintenance therapy, while the remaining 91 underwent early steroid discontinuation. Group A (n = 91) had steroids discontinued on postoperative day 6 and maintenance immunosuppression consisting of tacrolimus and mycophenolate mofetil. Group B (n = 34) received the same immunosuppression but was maintained on steroids indefinitely. Induction consisted of Thymoglobulin in African-Americans; all others received Simulect. RESULTS: At 1 year, patient and graft survivals were similar in both groups; there was a trend for reduction of acute rejection rates in group A (4% vs 12%). The incidence of PTDM was significantly lower in group A (7%) compared to group B (26%; P = .0209). The incidence of PTDM in group A was limited to Hispanic patients. African-Americans and Caucasians in group A did not experience PTDM (P = .005 compared to African-Americans in group B). CONCLUSION: A steroid-free protocol virtually eliminated the incidence of PTDM in African-Americans and Caucasians but had no effect on the development of PTDM in Hispanic recipients. Alternative immunosuppression may benefit this population.

Limited-dose Daclizumab versus Basiliximab: a comparison of cost and efficacy in preventing acute rejection.

The purpose of this study was to compare the efficacy and cost of the limited-dose Daclizumab regimen to that of the standard-dose Basiliximab regimen. Two antibody induction regimens were compared in patients aged 18 years and older who received renal transplants from January 2002 to September 2003 and completed interleukin (IL)-2R antibody induction with standard-dose Basiliximab (20 mg x 2 doses) or limited-dose Daclizumab (1 mg/kg x 2 doses). The primary outcome measure was the incidence of acute rejection. Secondary outcomes included cost, changes in serum creatinine level, and delayed graft function. Of the 46 patients randomized, 42 patients completed the 6-month follow-up. Mean serum creatinine level at time of discharge was originally higher in the limited-dose Daclizumab group than the standard-dose Basiliximab group (1.89 vs 1.57, respectively). By 1, 3, and 6 months, mean serum creatinine values were similar between both groups, with a trend toward lower mean serum creatinine values in the limited-dose Daclizumab group. The incidence of acute rejection was also similar between the groups (6% vs 7%). The average cost difference between the 2 regimens was approximately $715. This study suggests that a limited-dose Daclizumab regimen may be an efficacious and less costly alternative to the standard-dose Basiliximab regimen for antibody induction therapy following renal transplantation.

Immediate conversion from tacrolimus to cyclosporine in the treatment of posttransplantation diabetes mellitus.

Posttransplantation diabetes (PTDM) is a frequent complication of tacrolimus (TAC)-based immunosuppressive therapy after kidney transplantation. We investigated whether immediate conversion from TAC to Cyclosporine (CSA) could reverse or at least improve new-onset PTDM. Between February 2002 and February 2004, 28 adult kidney transplant recipients maintained on TAC were diagnosed with new-onset PTDM. Eight adult patients with new-onset PTDM were enrolled in the study and converted from TAC to CSA, the remaining 20 patients served as controls and were continued on the TAC-based immunosuppression. The conversion to CSA was performed immediately after establishing the diagnosis of PTDM at an average of 11 months posttransplantation. We did not document any episodes of acute rejection or worsening renal function after conversion. After conversion to CSA, among the 3 patients started on insulin, 1 has come completely off antidiabetic medications, whereas 1 required decreased doses of insulin, and the third has been converted to oral medications. Of the 5 patients originally on oral medications, 3 completely discontinued therapy, whereas the other 2 were well controlled on single-drug therapy at reduced doses. After a mean follow-up of 17 months, in the control group 9 of the 16 patients started on oral antidiabetics ultimately required insulin treatment and no patient could stop antidiabetic or insulin therapy. These findings indicate that conversion from TAC to CSA is a simple, safe, and efficacious way to reverse or at least improve PTDM.

Highly successful living donor kidney transplantation after conversion to negative of a previously positive flow-cytometry cross-match by pretransplant plasmapheresis.

Between July 2001 and November 2003, 16 patients with a positive flow-cytometry crossmatch to their potential living donor for kidney transplant were treated with desensitization protocol based on plasmapheresis and low-dose IVIg starting 1 week before the scheduled transplant. Twelve patients (75%) converted to negative crossmatch and were successfully transplanted. Immunosuppression consisted of induction with thymoglobulin, tacrolimus, mycophenolate mofetil, and steroids. Plasmapheresis and IVIg were continued on alternate days for the first postoperative week. The 1-year patient and graft survival was 100%. The rate of acute rejection was 41% (16% cellular and 25% humoral). All of the rejection episodes resolved with treatment. Combination of plasmapheresis and IVIg allows successful conversion from positive to negative flow-cytometry crossmatch in 75% of cases; after conversion, kidney transplant can be carried out with a high rate of success.

An assessment of P-glycoprotein expression and activity in peripheral blood lymphocytes of transplant candidates.

BACKGROUND: P-glycoprotein (P-gp) is involved in the transport of the xenobiotic immunosuppressive agents and many cytokines, such as IL-2 and IFN-gamma. Hence, P-gp activity on peripheral blood lymphocytes (PBLs) could affect the pharmacologic response to xenobiotic immunosuppressants and immune responsiveness. The objectives of this study were to (1) determine the level of P-gp expression and activity on PBLs of kidney transplant candidates; and (2) determine whether P-gp expression correlates with P-gp activity. METHODS: We measured P-gp expression and activity on CD3(+)/CD8(+), CD3(+)/CD4(+), B lymphocytes, and NK cells of 36 kidney transplant candidates using a flow cytometric assay. P-gp activity was determined for each subpopulation of cells by the ratio of the mean Rhodamine 123 fluorescence (MFI Rh123) in the presence of verapamil divided by the MFI Rh123 in the absence of verapamil. P-gp expression was noted as the percentage of P-gp(+) cells. RESULTS: NK cells exhibited the greatest amount of P-gp activity (MFI Rh123 = 20.2 +/- 16.4) compared with other cell populations (P < .05). P-gp efflux activity was also significantly elevated in CD3(+)/CD8(+) cells (13.9 +/- 10.5) compared with B lymphocytes (4.9 +/- 2.7; P < .05) and CD4/CD3(+) cells (2.4 +/- 1.0; P < .05). P-gp expression was significantly higher in B lymphocytes (11.7 +/- 9.5) and NK cells (10.2 +/- 7.3) when compared with CD3(+)/CD8(+) cells (7.3 +/- 6.9) and CD3(+)/CD4(+) cells (6.4 +/- 3.8). P-gp expression was highly variable and did not correlate with P-gp activity (P > .05). CONCLUSIONS: CD3(+)/CD8(+) cells and NK cells, exhibited significantly increased P-gp activity compared with the other cell populations. P-gp expression is not a good correlate of P-gp activity. These findings may have important implications for the use of immunosuppressive drugs posttransplant and immune responsiveness after transplantation.

Hepatic ischemia/reperfusion injury can be modulated with thymoglobulin induction therapy.

BACKGROUND: Thymoglobulin induction therapy has been shown to ameliorate delayed graft function and possibly decrease ischemia reperfusion injury in cadaver renal transplant recipients. This controlled randomized trial was designed to assess whether thymoglobulin also protects liver transplant recipients from ischemia reperfusion injury. PATIENTS AND METHODS: Twenty-two cadaver liver transplant recipients were randomized to receive either thymoglobulin (1.5 mg/kg per dose) during the anhepatic period and two doses every other day or no thymoglobulin. No differences in recipient or donor demographics were present. Maintenance immunosupression consisted of tacrolimus (or cyclosporine) and steroids for both groups. Donor biopsies were obtained during organ procurement, cold storage, and 1 hour after revascularization. Postoperative liver function tests were monitored. Early graft function, length of stay, patient and graft survival rates, incidence of primary nonfunction, and rate of rejection were assessed. RESULTS: Patient and graft survival at 3 months was 100%. There was no incidence of primary graft nonfunction and no need for retransplantation. The incidence of acute rejection was similar between the two groups. Although donor livers randomized to thymoglobulin had less optimal preimplantation biopsies, these recipients had significant decreases in ALT at day 1 compared to the control group (P = .02), near significant decreases of total bilirubin at day 5, and shorter length of hospitalization. CONCLUSION: Thymoglobulin allowed for more compromised liver grafts to be transplanted with less clinical evidence of ischemia reperfusion injury and improved function.

Do splanchnic viscera contribute to liver preservation reperfusion injury?

Preservation-reperfusion injury of hepatic allografts is thought to be associated with Kupffer cell activation and TNF release from the transplanted organ. Confirmation that the allograft is the source of this TNF in an in vivo model is difficult because of rapid equilibration of this cytokine into all compartments. A novel experimental design was devised to aid in accurate localization of the site of TNF release following a orthotopic liver transplant (OLT). In the first group (anhepatic), livers were removed from rats and splanchnic and systemic venous returns were then reestablished using a conduit of donor IVC and portal vein with a portasystemic shunt. In the second group (asplanchnic), the liver, stomach, pancreas, and intestine of the recipient were removed and a donor liver was reimplanted using the recipient IVC as the source of portal blood. The third (OLT-16) and fourth (OLT 8) groups underwent standard OLT with preservation times of 16 and 8 hr in 4 degrees C Euro-Collins solution, respectively. TNF levels were significantly increased in the OLT-16 group compared with the OLT-8 group. There were modest elevations of TNF in the anhepatic model, but the TNF in the asplanchnic model approached baseline. Absence of TNF in the asplanchnic group and a rise in TNF levels in the anhepatic group to that not significantly different from OLT-16 or OLT-8 suggest that a major source of TNF following preservation reperfusion may be the intestine.

Blood and graft eosinophilia as predictors of rejection in human liver transplantation.

This study attempts to define the relationship of blood and graft eosinophilia to acute hepatic allograft rejection. Sixty liver transplant patients were studied for the first 30 days postoperatively, with daily serum bilirubin and liver enzyme levels, white blood cell counts and differential counts, and biweekly core liver biopsies. Graft eosinophilia was established if 7% or greater of the cells infiltrating the portal triads were eosinophils. Blood eosinophilia is an absolute eosinophil count greater than 500 cells/mm3 occurring on any of the 5 days preceding the day of rejection. Acute rejection was diagnosed when 2 days of hepatic allograft dysfunction occurred with histologic evidence of rejection. The 2nd day of dysfunction with appropriate histologic findings was arbitrarily chosen as the day of rejection. Graft eosinophilia predicted rejection with 92% sensitivity and 98% specificity. Blood eosinophilia occurred on the average on the day of rejection and on the 2 preceding days, while graft eosinophilia occurred on the day of rejection and on 1 preceding day. Blood eosinophilia followed by graft eosinophilia specifically occurred in cases of rejection. Blood eosinophilia not followed by graft eosinophilia was not associated with rejection. Following treatment of rejection with high-dose corticosteroids, blood and graft eosinophil counts decreased markedly. In summary: (1) graft eosinophilia is very sensitive and specific for acute hepatic allograft rejection; (2) blood eosinophilia closely precedes and parallels graft eosinophilia specifically during acute hepatic allograft rejection; and (3) elevated blood and graft eosinophil counts are markedly reduced following treatment of rejection with high-dose corticosteroids.

An analysis of the determinants of hepatic allograft rejection using stepwise logistic regression.

Hepatic allograft rejection is currently diagnosed using both histologic and clinical criteria. The purpose of this study is to extract data from the allograft biopsy, which can establish the diagnosis of rejection with more precision. A total of 566 allograft biopsies were examined in 56 patients following orthotopic liver transplantation, and 35 variables were examined. Using stepwise logistic regression, only six of these variables affected the diagnosis of rejection. These were portal tract spillover, portal tract eosinophilia, portal vein endothelialitis, portal tract neutrophilia, central vein endothelialitis, and cholestasis. Coefficients of these variables were determined, and could be used to calculate the probability of rejection for a given biopsy. Using this model the probability of having rejection can be calculated using histologic data alone.

Leflunomide in experimental transplantation. Control of rejection and alloantibody production, reversal of acute rejection, and interaction with cyclosporine.

Leflunomide is a compound recently shown to reduce T and B cell-mediated responses in a number of experimental rat, mouse, and human systems. To explore its potential as an immunosuppressant, we studied leflunomide in 128 Brown-Norway/Lewis cardiac transplants and in 48 unoperated Lewis rats. At doses ranging from 0.63 mg/kg to 10 mg/kg given for 7 days, leflunomide significantly prolonged graft survival compared with controls. When cyclosporine or leflunomide was given for 21 days at a dose of 5 mg/kg, indefinite graft survival occurred in 3/6 animals receiving leflunomide but in none of the 21-day cyclosporine-treated animals. When acute rejection was allowed to develop for four days in untreated rats, leflunomide but not cyclosporine reversed the rejection, returning histology to a normal appearance by seven days. Alloantibody responses measured in microcytoxicity assays as well as total allospecific IgG and IgM in the rejecting animals also were returned to baseline levels by leflunomide but not cyclosporine. When both drugs were used together, a synergistic effect was observed at low doses of both drugs. Pharmacokinetics studies showed that their combined use for up to 28 days did not affect the trough levels of cyclosporine or cyclosporine elimination, suggesting that the synergistic effect was not caused by reduced elimination. The toxicity of each drug was negligible in a group of 32 rats receiving the drugs alone or in combination as measured by serial observation of general appearance, testing of serum ALT, AST, bilirubin, creatinine, white blood cell counts, hemoglobin, and gross necropsy appearance. Weight gain was slightly reduced by both drugs but combined drug use did not alter the pattern. The results of these experiments show leflunomide to be a potent, well-tolerated immunosuppressant, synergistic in its activity with cyclosporine, and would seem to encourage a closer look at this drug for potential use in man.

The role of ultraviolet B-irradiated leukocyte transfusions and cyclosporine in intestinal transplantation.

To explore the efficacy of ultraviolet B-irradiated donor-specific leukocyte transfusions (UV-DSLT) with short-term cyclosporine to control intestinal allograft rejection, 75 adult Lewis (RT1l) rats underwent total small-intestinal transplantation from Brown-Norway (RT1n) donors. Recipients were randomly divided into ten treatment and control groups utilizing various combinations of donor-specific and third-party (Wistar-Furth, RT1u) leukocyte transfusions (TPLT), with or without transfusion UVB irradiation, and either alone or in combination with short-term cyclosporine administration (5 mg/kg intramuscularly on days -7, 0, 1, and 2 relative to transplantation). Leukocytes (10(8) cells) separated from a spleen cell suspension were infused on day -7. Certain transfused leukocytes were treated with 12,000 joules/m2 of UVB irradiation. Groups were monitored for mean survival time (MST) and cause of death. UV-DSLT alone (MST = 19.8 +/- 4.6) or in combination with cyclosporine (UV-DSLT+CsA, MST = 53.1 +/- 22.5) significantly (P less than 0.003-0.0002, Mantel-Cox) prolonged recipient survival when compared with appropriate controls (i.e., no treatment, MST = 11.2 +/- 3.4; CsA, MST = 17.2 +/- 9.0; UV-TPLT, MST = 12.4 +/- 4.0; and UV-TPLT+CsA, MST = 25.1 +/- 9.7) No significant increase in graft-versus-host disease occurred in any group, with 85% (64/75) of the recipients dying of acute rejection. Conversely, the UV-DSLT+CsA group had a significant increase (9/11; chi-square, P less than 0.0001) in chronic rejection. Because UV-DSLT+CsA improved survival as compared with third-party controls, a limited donor-specific unresponsiveness may have been induced. Furthermore, this treatment produces a consistent, chronic rejection rodent intestinal allograft model.

Morphometric inflammatory cell analysis of human liver allograft biopsies.

To quantitate the inflammatory cell response within the portal tracts of liver allografts during acute rejection, we retrospectively and in a blinded fashion reviewed 431 biweekly, protocol, core allograft biopsies in 58 consecutive adult recipients. Following the determination of the cross-sectional area of each portal tract, the number of eosinophils, neutrophils, and lymphocytes therein was tabulated. The average number, percentage, and density of each type of portal inflammatory cell were calculated for each biopsy. Each biopsy was prospectively and independently classified as either associated (REJ+) or not associated (REJ-) with acute rejection. Acute rejection consisted of simultaneous allograft dysfunction and qualitative pathologic findings of acute rejection. Biopsies obtained during periods of normal allograft function or during episodes of dysfunction due to other causes were classified as not associated with rejection (REJ-). Ninety biopsies were classified as associated with acute rejection (REJ+) while 241 biopsies were classified as not associated with acute rejection (REJ-). In general, the average portal-tract number, percentage, and density of all inflammatory cells were significantly increased in biopsies associated with acute rejection. In contrast, only the portal-tract eosinophil values were consistently predictive of acute rejection following receiver-operating characteristic curve analysis (sensitivity = 82-86%, specificity = 91-92%). This quantitative method of allograft assessment appears to improve the objectivity of the serial biopsy protocol. By using this method, we found the eosinophil's appearance within the portal tracts to be a dependable indicator of acute rejection.

Induction of tolerance to small bowel allografts in high-responder rats by combining anti-CD4 with CTLA4Ig.

This study was designed to investigate the effectiveness of combined perioperative anti-CD4 and human (h)CTLA4Ig therapy in preventing allorejection of small bowel transplantation in high-responder Lewis rat recipients of ACI grafts. Anti-CD4 (5 mg/kg x 4 days) or hCTLA4Ig (0.5 mg/rat x 2 days) therapy alone delayed, but did not prevent, allograft rejection after small bowel transplantation of ACI into Lewis rats. All grafts were rejected in 18 and 10 days, respectively. However, a regimen of anti-CD4 (5 mg/kg x 4 days) combined with hCTLA4Ig (0.5 mg/rat x 2 days) allowed indefinite survival of ACI small bowel allografts. Second donor-matched heart grafts were permanently accepted, whereas third-party (Sprague-Dawley) heart allografts were rejected by the tolerant recipients. These data suggest that these two reagents produced a synergistic effect in preventing allorejection of small bowel transplantation.

Leflunomide, a novel immunosuppressive agent. The mechanism of inhibition of T cell proliferation.

Leflunomide is a novel immunomodulating drug that has recently been demonstrated to prevent acute rejection and reverse ongoing rejection of kidney and cardiac allografts in rats. In vitro studies here demonstrate that leflunomide suppresses proliferation of human PBL stimulated with (1) allogeneic PBL in a one-way MLR (50% inhibition with 50-25 microM); (2) anti-CD3 mABs plus PMA (50% inhibition with 70 microM leflunomide); and (3) anti-CD28 mABs plus PMA (50% inhibition with 65 microM leflunomide). In contrast, CsA only inhibited T cell proliferation stimulated by anti-CD3 plus PMA. Leflunomide partially inhibited IL-2 production of T cells stimulated with anti-CD3 plus PMA or anti-CD28 plus PMA, whereas CsA completely inhibited IL-2 production by T cells stimulated by the CD3 pathway and only partially inhibited IL-2 production by T cells stimulated by the CD28 pathway. Because comparable levels of IL-2 were produced by CD28-stimulated T cells treated with either CsA or leflunomide, but no inhibition of proliferation was observed in the CsA-treated cultures, we hypothesized that the lowering of IL-2 levels was not the mechanism by which leflunomide inhibited T cell proliferation. This hypothesis was supported by the observations that exogenous IL-2 failed to restore the T cell proliferation in the presence of leflunomide. Loss of T cell responsiveness to IL-2 in the presence of leflunomide was not due loss of expression of IL-2 receptors. Collectively, our data suggest that inhibition of T cell proliferation by leflunomide occurs via inhibition of responsiveness to IL-2.

An evaluation of leflunomide in the canine renal transplantation model.

Leflunomide is an isoxazole with newly discovered immunosuppressive properties. Its mechanism of action operates later in the cell cycle than cyclosporine and appears to interfere with lymphocyte IL-2 responsiveness. With the encouraging results from in vitro and small-animal studies, we subjected leflunomide to the rigorous canine renal transplantation model in a dose response protocol. Thirty-eight female mongrel dogs underwent renal transplantation and bilateral nephrectomy. Immunosuppression was stratified from controls with no immunosuppression to monotherapy with leflunomide at 2, 4, 8, and 16 mg/kg/day given orally and in a combination therapy with cyclosporine. To evaluate its toxicity while maintaining a low constant blood level, eight dogs were treated by continuous intravenous infusion at doses of 2, 4, 6, and 8 mg/kg/day. The mean survival time for nonimmunosuppressed controls (n = 2) was 9 days, leflunomide 2 mg/kg/day (n = 2) was 9 days, leflunomide 4 mg/kg/day (n = 4) was 16 days, leflunomide 8 mg/kg/day (n = 5) was 28 days, leflunomide 16 mg/kg/day (n = 7) was 21 days. Cyclosporine alone at 10 mg/kg/day (n = 4) resulted in a mean survival time of 13 days. The mean survival time with the combination of cyclosporine 10 mg/kg/day with leflunomide 4 mg/kg/day (n = 6) was 68 days. The mean survival time for continuous intravenous leflunomide 2 mg/kg/day (n = 2) was 10 days; for leflunomide 4 mg/kg/day, 20 days; for leflunomide 6 mg/kg/day, 14 days; and leflunomide 8 mg/kg/day, 21 days. The mean serum trough levels of leflunomide ranged from 10 micrograms/ml at the 2 mg dose to 55 micrograms/ml for the 16 mg dose, levels that have been well tolerated in man. Leflunomide at 16 mg/kg/day reliably prevented acute allograft rejection, but the dogs died of inanition with normal renal function. Leflunomide at a nontoxic dose of 4 mg/kg/day extended survival to 16 days, but all dogs died of rejection. A combination of inadequate doses of leflunomide (4 mg/kg/day) and cyclosporine (10 mg/kg/day) resulted in all animals having normal renal function and weight for > or = 30 days. Even at a high dose of 16 mg/kg/day, no viral or bacterial infections were noted. These observations in a canine system add to the growing enthusiasm for the evaluation of leflunomide in human transplantation.

Leflunomide controls rejection in hamster to rat cardiac xenografts.

Leflunomide is an isoxazole derivative that has the ability to prevent acute rejection of cardiac, renal, and skin transplants in strongly rejecting rat models. Furthermore, leflunomide is able to interact synergistically with CsA to inhibit allograft rejection and also reverse ongoing allograft rejection. In vitro studies suggest that the mechanism of action of leflunomide is via an interruption of cytokine signaling in T cells. This study defines the ability of leflunomide to prevent and reverse rejection of concordant xenografts. One hundred nine adult Lewis rats in 13 groups received abdominal heterotopic cardiac transplants from Golden Syrian hamsters. The xenograft survived 3.9 +/-0.3 days without treatment. When leflunomide was given at 2.5, 5, 10, 15, or 20 mg/kg by gavage daily, the cardiac xenograft survivals were 5.0 +/- 0.6, 8.0 +/- 3.0, 52.0 +/- 20.2, 76.5 +/- 21.14, and 58.9 +/- 28.1 days, respectively. The survival rates were 4.0 +/- 0 and 27.7 +/- 28.7 days when CsA was given at 10 and 20 mg/kg i.m., respectively. The combination of CsA at 10 mg/kg with leflunomide at 10 mg/kg or 5 mg/kg prolonged cardiac xenograft survival to 106.0 +/- 50.2 days and > 90 days, respectively. There were no observable side effects in the latter combination. Histologic studies of untreated graft hearts 4 days after transplantation revealed infarction of myocardium and severe RBC extravasation. In contrast, the rejected hamster hearts from long-term survivors showed massive mononuclear cell infiltration and myocardium fibrosis in contrast to the early rejected picture. Therapy with leflunomide begun on day 2 reversed these rejection responses by day 6. In addition, the increase in allospecific IgM titers observed on day 2 was reversed, and the allospecific IgM to IgG isotype switch that occurred in untreated animals was prevented by leflunomide. These observations demonstrate that leflunomide, at nontoxic doses, effectively controlled acute rejection of concordant xenografts and synergistic immunosuppressive effect was achieved with leflunomide and CsA.