Academic careers and lifestyle characteristics of 171 transplant surgeons in the ASTS.

This manuscript reports the demographics, education and training, professional activities and lifestyle characteristics of 171 members of the American Society of Transplant Surgeons (ASTS). ASTS members were sent a comprehensive survey by electronic mail. There were 171 respondents who were 49 ± 8 years of age and predominantly Caucasian males. Female transplant surgeons comprised 10% of respondents. ASTS respondents underwent 15.6 ± 1.0 years of education and training (including college, medical school, residency and transplantation fellowship) and had practiced for 14.7 ± 9.2 years. Clinical practice included kidney, pancreas and liver organ transplantation, living donor surgery, organ procurement, vascular access procedures and general surgery. Transplant surgeons also devote a significant amount of time to nonsurgical patient care, research, education and administration. Transplant surgeons, both male and female, reported working approximately 70 h/week and a median of 195 operative cases per year. The anticipated retirement age for men was 64.6 ± 8.6 and for women was 62.2 ± 4.2 years. This is the largest study to date assessing professional and lifestyle characteristics of abdominal transplant surgeons.

Renal Transplantation in the Setting of Prior Urinary Diversion: A Case of Poorly Differentiated Adenocarcinoma in an Ileal Conduit.

Though rare, renal transplantation into a bowel containing urinary diversion is necessary in select clinical situations. Compared to renal transplant patients with functional native bladders, patients with urinary diversion have comparable long-term graft and patient survival rates. However, compounding the increased risk of malignancy in those on chronic immunosuppression are the inherent risks of urinary diversion. We present a case report of a high grade adenocarcinoma with neuroendocrine differentiation arising in an ileal conduit and discussion on the pathophysiology, management, and screening of this highly select population.

Alternative splicing of the tyrosinase gene transcript in normal human melanocytes and lymphocytes.

We have identified and isolated ectopically expressed tyrosinase transcripts in normal human melanocytes and lymphocytes and in a human melanoma (MNT-1) cell line to establish a baseline for the expression pattern of this gene in normal tissue. Tyrosinase mRNA from human lymphoblastoid cell lines was reverse transcribed and amplified using specific "nested" primers. This amplification yielded eight identifiable transcripts; five that resulted from alternative splicing patterns arising from the utilization of normal and alternative splice sequences. Identical splicing patterns were found in transcripts from human primary melanocytes in culture and a melanoma cell line, indicating that lymphoblastoid cell lines provide an accurate reflection of transcript processing in melanocytes. Similar splicing patterns have also been found with murine melanocyte tyrosinase transcripts. Our results demonstrate that alternative splicing of human tyrosinase gene transcript produces a number of predictable and identifiable transcripts, and that human lymphoblastoid cell lines provide a source of ectopically expressed transcripts that can be used to study the biology of tyrosinase gene expression in humans.

Identification of a novel transcript produced by the gene responsible for the Hermansky-Pudlak syndrome in Puerto Rico.

Hermansky-Pudlak Syndrome (HPS) is a rare, autosomal recessive disorder that is characterized by oculocutaneous albinism, a predisposition to mild bleeding caused by storage-pool deficient platelets, and a ceroid storage disorder. A gene responsible for HPS in Puerto Rico maps to chromosome 10q2 and isolation of the gene has been reported. We have now identified a variant HPS cDNA that contains the same 5' sequence as the published HPS gene and a unique 3' sequence. Analysis of genomic DNA suggests that the two cDNA are derived from alternative transcripts of a single gene; two polyadenylated transcripts were found in normal human melanocytes, human bone marrow cells, human melanoma cells, lymphoblastoid cell lines, and megakaryocytic leukemia cells by reverse transcriptase polymerase chain reaction and northern analysis. The splicing exhibited by this gene is identical to the splicing found to produce two alternative transcripts of the Chediak-Higashi Syndrome gene, another pigment disorder exhibiting platelet storage pool deficiency. These studies show that the HPS gene on chromosome 10 is complex and may have more than one biologically active transcript.

Frequency of hyperkalemia in recipients of simultaneous pancreas and kidney transplants with bladder drainage.

Hyperkalemia is the most frequent electrolyte abnormality found in whole organ transplant recipients receiving either cyclosporine (CsA) or tacrolimus (FK506). Recipients of a simultaneous pancreas kidney (SPK) transplant with bladder drainage may be particularly susceptible to hyperkalemia secondary to sodium loss from the bladder-drained pancreas, leading to decreased sodium delivery to potassium secretory sites of the kidney. We looked at the incidence of hyperkalemia in 34 type I diabetic SPK recipients transplanted at our center over the period from 1993 to 1995 and compared this with a cohort of 25 type I diabetic recipients of a kidney alone (K(Tx)) transplant. The incidence of hyperkalemia was 73.5% in recipients of an SPK, while it was 44% in K(Tx) recipients (P<0.05). CsA levels were higher, on average, in the SPK group (339 ng/ml+/-62 versus 272 ng/ml+/-58 in the K(Tx) group, P<0.05). However, CsA levels were not different between groups at the time of hyperkalemia, 320+/-74 versus 298+/-49 for SPK and K(Tx), respectively. CsA levels at the time of hyperkalemia were not different from those at the time of normokalemia. Other medications, serum bicarbonate, and renal function were not different in the groups. SPK recipients appear to have a greater incidence of hyperkalemia than kidney alone transplant recipients. This difference cannot be explained by higher acute CsA levels, other medications, or worse renal function. The increased incidence of hyperkalemia may, in part, be secondary to decreased sodium delivery to the transplanted kidney.

Risk factors and impact of cytomegalovirus disease in simultaneous pancreas-kidney transplantation.

BACKGROUND: The relevance of cytomegalovirus (CMV) in simultaneous pancreas kidney (SPK) transplant recipients in the modern era of immunosuppression and antiviral therapeutics is largely unquantified. We sought to determine the risk factors of CMV disease and its impact on SPK transplant outcomes in recipients all receiving a consistent regime of maintenance immunosuppression and CMV prophylaxis. METHODS: This is a retrospective, single center study of 100 consecutive SPK transplant recipients. All received maintenance immunosuppression with mycophenolate mofetil, tacrolimus, and prednisone. CMV prophylaxis consisted of a short course of parenteral gancyclovir followed by oral gancyclovir. Recipients at high-risk (D+/R-) for CMV also received CMV hyperimmune globulin. Multivariate analysis of risk factors for CMV disease and risk factors for adverse outcomes in SPK transplantation were determined. The effect of duration of prophylaxis on timing and severity of CMV disease in high-risk (D+/R-) SPK transplant recipients was also evaluated. RESULTS: The actual 1-year rate of CMV disease was 17.0% (12.0% noninvasive, 5.0% tissue invasive); and according to donor and recipient CMV serological status was: D-/R+: 0%; D-/R-: 2.8%; D+/R+: 25.6%; and D+/R-: 40.6%. Multivariate analysis showed transplantation of organs from a donor with positive CMV serology to be predictive of CMV disease with a relative risk of 63.37 (P=0.0052). In the high-risk (D+/R-) subgroup, the duration of prophylactic therapy delayed onset of CMV disease, but had minimal effect on severity. Invasive CMV disease was an independent predictor of mortality but did not decrease kidney or pancreas allograft survival. CONCLUSIONS: Outcomes of SPK transplantation have improved in the current era of modern immunosuppression, yet CMV remains an important pathogen. The serological status of the organ donor and the duration of CMV prophylaxis are predictive of who and when CMV disease may occur. Nevertheless, new strategies that reduce risk and severity of CMV disease are still needed.

Beyond hyperacute rejection. Accelerated rejection in a discordant xenograft model by adoptive transfer of specific cell subsets.

If hyperacute rejection is prevented in the guineapig (GP)-to-Lewis rat (Lew) cardiac xenograft (CXg) model, an accelerated rejection involving cellular infiltration occurs in 3 to 4 days. In previous work using an adoptive transfer model, we found that this accelerated rejection was facilitated by either sensitized splenocytes or sensitized serum. In the current study, in an attempt to determine which splenocyte subset(s) facilitated this process, sensitized splenocytes, with or without subset depletion were injected, into complement- and natural antibody-depleted Lew recipients of GP CXgs. Graft survival was 4.18 +/- 0.75 days with no injection (n = 11), 4.13 +/- 0.99 days with naive splenocytes (n = 8), 1.80 +/- 0.45 days with sensitized splenocytes (n = 5), 2.67 +/- 1.03 days with CD4(W3/25+) depletion of the sensitized splenocytes (n = 6), 3.13 +/- 0.84 days with CD8(OX8+) cell depletion (n = 8), 4.70 +/- 0.68 days with macrophage depletion (n = 10), and 4.22 +/- 0.41 days with B cell depletion (n = 9). Cellular infiltrates, hemorrhage, myocyte necrosis, and endothelial deposition of IgG, IgM, and fibrin were seen in rejected grafts. In most groups, infiltrating cells consisted of CD4 (W3/25+), CD8 (OX8+), IL2R+ cells, macrophages, and natural killer (NK) cells. However, in the macrophages-depleted group, activated (ED2+) macrophages and NK cells were significantly reduced. Total IgM, anti-GP IgM, and anti-GP IgG rebounded in all groups over several days but were not consistent at the time of rejection. Lewis rats rejecting GP CXgs early had lower final titers than those rejecting later. Total IgG titers rebounded to baseline by posttransplant day 1 and were therefore similar in all groups at the time of rejection. These findings suggest that this accelerated rejection requires interaction between macrophages and B cells, since depletion of either significantly alters the rejection tempo. A possible explanation is that xenoreactive IgG antibodies, synthesized by sensitized B cells, bind their target antigens--but also bind sensitized macrophages through their Fc region, thus causing rejection by antibody-dependent cell-mediated cytotoxicity.

Removal of baboon and human antiporcine IgG and IgM natural antibodies by immunoadsorption. Results of in vitro and in vivo studies.

The safe and effective removal of xenoreactive antibodies in the peritransplant period is likely to be critical for the clinical application of xenotransplantation involving disparate donor species, such as the pig. In an effort to develop an improved method for antibody removal in xenotransplantation, we have studied reusable antihuman antibody (Ig) columns in vitro and in vivo. Two types of columns were tested: (1) an antihuman Ig column containing polyclonal sheep antihuman IgG (heavy- and light-chain-specific) conjugated to sepharose CL-4B (Ig-Therasorb), and (2) an antihuman Ig column using polyclonal antihuman IgM (mu-chain-specific) conjugated to sepharose. Passage of human or baboon plasma through the Ig-Therasorb column resulted in 97.5% and 78.4% mean reductions in total IgG and IgM, respectively. Reductions in total IgG and IgM correlated with lowering of antipig IgG (54-486 fold) and IgM (9-54 fold) antibody titers as assessed by pig endothelial cell ELISA. The ability of the Ig-Therasorb to significantly reduce IgM may be attributed to the light chain specificity of this column. With the anti-IgM column, marked reductions in total (82.6-83.9%) and antipig (27-54 fold) IgM in human and baboon plasma occurred, while levels of total and xenoreactive IgG were slightly affected. Other than a dilutional effect, neither column resulted in significant reduction in albumin, fibrinogen, factor 5, and factor 8. Repeated in vivo use of either column in baboons achieved reductions in IgG and IgM that closely followed the results of our in vitro studies. No subject morbidity or mortality occurred. Use of the Ig-Therasorb column with immunosuppression in two baboons receiving pig renal xenografts achieved sustained reductions in antipig antibodies and prevented hyperacute rejection. Subjects were sacrificed at 11 and 13 days posttransplant with functioning xenografts and were found to have no evidence of vascular xenograft rejection. We conclude that anti-Ig columns represent a safe and effective method for antibody removal, without several of the limitations of other antibody removal techniques. Also, columns appear to be safe for repeated antibody removal in the posttransplant period.

Combined transplantation of small and large bowel. FK506 versus cyclosporine A in a porcine model.

Clinically, FK506 is superior to CsA after solitary small bowel transplantation (SBTx). Development of diarrhea after SBTx has been the rationale for adding the colon to small bowel grafts. However, the additional lymphoid and bacterial content transferred with total small plus large bowel transplants (TBTx) might aggravate the alloimmune response-rejection and graft-versus-host disease (GVHD)-and increase the risk of infection. We studied the incidence of rejection, GVHD, and infection after TBTx and the impact of CsA versus FK506. We performed orthotopic TBTx with portal drainage after total enterectomy in outbred Yorkshire Landrace pigs, divided into 3 groups: control pigs (n=6) received no immunosuppression; CsA pigs (n= 14) received CsA (5 mg/kg), antilymphocyte globulin (10 mg/kg for 10 days), prednisone (2 mg/kg), and AZA (2.5 mgtkg); and FK506 pigs (n=9) received FK506 (0.2 mg/kg) and prednisone (2 mg/kg). Trough CsA whole blood levels were >400 ng/ml for the first 7 days and >200 ng/ml thereafter. FK506 levels were > 15 ng/ml. We excluded from further analysis 5 early deaths (<3 days) due to anesthesiologic (n=2) or technical reasons (n=3). Median survival of control pigs was 9.5 days (range, 4-13). Cyclosporine did not extend survival: median, 9 days (range, 5-31) (P=0.6). FK506 prolonged survival: median, 37 days (range, 21-49) (P<0.001 vs. control and CsA pigs). Of FK506 pigs, 60% gained weight (+75 g/day), whereas 100% of controls and 75% of CsA pigs lost weight (-550 g/day and -300 g/day, respectively). All control pigs died of rejection within 2 weeks versus none of the FK506 pigs. However, 36% of CsA pigs died of rejection. Groupwise comparison showed less rejection in FK506 versus control pigs (P<0.001) and in FK506 versus CsA pigs (P<0.03), but no difference between CsA and control pigs. None of the control pigs died of GVHD versus 18% of CsA pigs (by day 31) and 37% of FK506 pigs (by day 49). Groupwise comparison showed increased GVHD in FK506 versus control pigs (P<0.001) and a tendency toward increased GVHD in FK506 versus CsA pigs (P=0.08). None of the control pigs died of infection alone versus 22% of CsA pigs (by day 31) and 67% of FK506 pigs (by day 49). Groupwise comparison showed increased infection in FK506 versus control pigs (P<0.001). We detected significant endotoxemia early and late postoperatively. But we saw no specific correlation between endotoxemia, rejection, GVHD, or infection. Based on this study, we have drawn several conclusions: (1) In untreated pigs, TBTx provokes a severe rejection response, but no lethal GVHD. (2) Cyclosporine and particularly FK506 pigs have a high incidence of infection and lethal GVHD, a complication that we had not seen after solitary SBTx. (3) FK506 is superior to CsA in controlling rejection and in prolonging graft and recipient survival; FK506, however, does not reduce GVHD, but rather tends to augment it. (4) TBTx causes endotoxemia. As with solitary SBTx, FK506 is superior to CsA after TBTx. However, longterm survival is difficult to achieve on FK506 recipients because of the development of GVHD and infection.

Acyclovir triphosphate inhibits the diagnostic polymerase chain reaction for cytomegalovirus.

Immunocompromised patients are frequently treated with guanine analogs such as acyclovir and ganciclovir. Acyclovir triphosphate, the active intracellular metabolite of acyclovir, exerts its antiviral effect by inhibiting herpesviral DNA polymerases through premature chain termination. PCR has recently been used for early detection of cytomegalovirus. However, we and others have experienced false-negative results for cytomegalovirus-PCR in patients on both acyclovir and ganciclovir. The impact of these agents on PCR assay is unknown. In an attempt to investigate the role of guanosine analogs in these false-negative results, we exposed the DNA-PCR for murine beta-actin, a murine CMV IE gene sequence, and a human CMV IEA1 product, to phosphorylated acyclovir derivatives. Varying concentrations of acyclovir-5'-triphosphate (final: 70-6000 microM) in the reaction mix resulted in an absence of detectable product at or above 490-670 microM. Inhibition was not observed with up to 1400 microM acyclovir-monophosphate. Increasing the Taq concentration to 10 units/100 microL stopped the inhibition. Our data demonstrate that acyclovir-5'-triphosphate inhibits PCR amplification of various gene products in a concentration-dependent manner. Furthermore, this inhibition appears to be specifically directed against the Taq polymerase and can be completely reversed by higher concentrations of the enzyme. Thus, false-negative PCR results for a viral gene product in patients under prophylaxis/treatment with acyclovir could potentially be due to contamination by acyclovir triphosphate. Therefore, negative PCR results in these patients need be interpreted with caution.

A prospective study of FK506 versus CsA and pig ATG in a porcine model of small bowel transplantation.

Rejection remains a major barrier to successful bowel transplantation, and immunosuppressive protocols are far from standardized. In 88 nonrelated outbred pigs, we compared the effects of two immunosuppressive regimens--one with FK506, the other with cyclosporine (CsA) and pig antithymocyte globulin (ATG)--on incidence and severity of rejection in the early, critical posttransplant period. Group A (n = 14) was nonimmunosuppressed (controls). Group B (n = 17) received pig ATG (10 mg/kg/day x 10 days), CsA (3 mg/kg/day), prednisolone (2 mg/kg/day), and azathioprine (2.5 mg/kg/day); prednisolone and azathioprine were each reduced by 50% at 8 and 15 days posttransplant. Trough CsA whole-blood concentrations were > or = 400 ng/ml for the first 7 days, > or = 200 ng/ml thereafter. Group C (n = 13) received FK506 (0.2 mg/kg/day) and prednisolone (2 mg/kg/day); prednisolone was reduced by 50% at 8 and 15 days. FK506 whole-blood concentrations were > or = 20 ng/ml. All immunosuppression in groups B and C was given intravenously. We performed orthotopic small bowel transplants with systemic venous drainage. Recipient bowel was resected distal to the second portion of the duodenum and proximal to the rectum at transplant; bowel continuity was restored by duodenojejunostomy; ileostomy was created distally to allow access for daily biopsies. We graded interstitial and vascular rejection separately, according to a scoring system (no, mild, moderate, and severe rejection). Rejection-free graft survivals at 7, 14, and 21 days posttransplant were 38%, 19%, and 0% in group A; 93%, 93%, and 62% in group B; and 100%, 91%, and 82% in group C (P < 0.001). Comparing rejection in the immunosuppressed groups, group C (FK506) had a stronger tendency toward rejection than group B (CsA-ATG); significant differences between groups B and C were, however, noted only on individual days posttransplant, not over time. The death rate due to irreversible rejection was not significantly different in groups B and C (P = 0.8), but was significantly better in both of these immunosuppressed groups than in group A (P < 0.001). Pig survival was significantly longer in group C than in B (P = 0.001) due to a lower infection rate in group C. Posttransplant serum interleukin 2 and 7 levels did not correlate with rejection grades. Graft-versus-host reaction was noted only in the skin in 29% of group A, 73% of group B, and 77% of group C pigs; liver and native bowel were not involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Laparoscopic live donor nephrectomy--is it safe?

BACKGROUND: Laparoscopic live donor nephrectomy (LDN) is a less invasive alternative to open nephrectomy (ODN) for living kidney donation. Concerns have been raised regarding the safety of LDN, the short and long term function of kidneys removed by LDN, and a potential higher incidence of urologic complications in LDN transplant recipients. METHODS: Between October 1997 and May 1999, 80 LDNs were performed at our center. All patients were followed longitudinally with office visits and telephone interviews. These LDNs were compared with 50 ODN performed from January 1996 to October 1997. RESULTS: LDN procedures took significantly longer than ODN (4.6 vs. 3.1 hr). However, LDN was associated with significant reduction in i.v. narcotic use, a rapid return to diet, and shorter hospital stay. Of the 80 LDN procedures, a total of 75 (94%) were completed laparoscopically. Five patients were converted to laparotomy: three for hemorrhage and two for complex vascular anatomy. ODN conversion was associated with large donor body habitus and/or obesity. Seven LDN patients had minor complications and 4 had major complications. All major complications consisted of vascular injuries (2 lumbar vein injuries, 1 renal artery, and 1 aortic injury). All patients made complete recoveries. All LDN kidneys functioned immediately posttransplant. We have observed 100% patient and 97% 1-year actuarial graft survival in LDN transplant recipients. There have been no short-or long-term urologic complications in this series. CONCLUSION: With increasing experience and standardization of technique, LDN is a safe and effective procedure. Patients undergoing LDN demonstrate clinically significant, more rapid postoperative recoveries and shorter hospital stays than ODN patients. Excellent initial graft function and long-term graft survival have been observed with LDN kidneys. Urologic complications can be avoided. LDN has become the preferred surgical approach for living kidney donation at our center.

Mycophenolate mofetil and tacrolimus as primary maintenance immunosuppression in simultaneous pancreas-kidney transplantation: initial experience in 50 consecutive cases.

BACKGROUND: The current study examines the use of mycophenolate mofetil (MMF) and tacrolimus as primary immunosuppression in simultaneous pancreas-kidney (SPK) transplantation. In addition, analyses of the rates of conversion from one immunosuppressive agent to another, and its subsequent consequences with respect to outcomes were determined. Quality of graft function, infections, and effect on preexisting essential hypertension are also described. METHODS: Immunosuppression consisted of quadruple therapy with antithymocyte globulin induction, tacrolimus, MMF, and prednisone. Patient and graft survival and rejection rates in 50 consecutive SPK recipients, followed for a minimum of 3 months and a mean of 14 months (range: 3-34 months), are described. RESULTS: Thirty-nine of 50 (78%) patients tolerated the MMF/tacrolimus combination long-term (mean duration of follow-up: 14+/-7 months). Nine of 50 patients (18%) were converted to Neoral, and 4 patients were converted to azathioprine as a substitute for MMF. The 2-year actuarial patient, kidney, and pancreas survival rates were 97.7%, 93.3%, and 90.0%, respectively. At 6 months after transplant, the overall incidence of acute rejection was 16%. There was a statistically significant (P< or =0.04, Cox-Mantel test) difference in the rate of rejection associated with conversion to Neoral. The incidence of rejection 6 months after transplant in the group maintained on MMF/tacrolimus was 10.2% vs. 44.4% in the group converted to Neoral (P< or =0.04, Cox-Mantel test). Overall, the 1-year actuarial cumulative incidence of tissue-invasive cytomegalovirus disease was 6.6%. There were no cases of fungal infections or post-transplant lymphoproliferative disorders. One patient developed Kaposi's sarcoma 10 months after transplant. With respect to hypertensive disease, 60% (12/20) of the patients who required pharmacologic control of blood pressure before transplant were off all antihypertensive medications at 1 year after transplant. An additional 20% (4/20) of patients had a reduction in the number of medications required to control blood pressure at 1 year after transplant. CONCLUSIONS: We conclude that the combination of MMF and tacrolimus as primary immunosuppression for SPK transplantation results in excellent patient and graft survival rates, a very low rate of acute rejection, and low rates of infection and malignancy.

The role of PCR in the diagnosis and management of CMV in solid organ recipients: what is the predictive value for the development of disease and should PCR be used to guide antiviral therapy?

Cytomegalovirus remains a significant source of morbidity and mortality in immunocompromised hosts. The increased sensitivity of molecular diagnostic techniques (PCR, antigenemia) has resulted in our ability to detect viral replication earlier in the posttransplant period, before the onset of symptoms. With the advent of effective antiviral therapy, "preemptive therapy," guided by sensitive, early and specific predictors of CMV disease, has become a realistic objective. Although multiple studies have analyzed the sensitivity and specificity of these tests, their predictive value for the development of disease has not been defined. The purpose of this study was to evaluate the predictive value of a positive CMV PCR in the setting of solid abdominal organ transplantation. A total of 476 PCR assays were performed on 134 transplant recipients (102 kidney, 19 kidney/pancreas, 11 liver, 2 other) either as protocol serial samples or as dictated by clinical events. All samples were concomitantly analyzed using standard virological assays for CMV including culture, shell vial, and serology. Patients with any CMV seropositive donor/recipient (D/R) combination received ganciclovir prophylaxis in conjunction with antilymphocyte induction for 14 days. No subsequent CMV prophylaxis was used. The positive predictive value was 55% in all seropositive donor/recipient combinations. The highest risk group (seronegative recipient of seropositive donor) showed the highest positive predictive value, whereas seropositive recipients of either seropositive or seronegative donors showed positive predictive values of 45% and 25%, respectively. Negative predictive value was 100% for all groups. Early detection of CMV infection has important implications for patient management, including preemptive therapy, which can be guided by PCR, especially in high risk (D+/R-) patients.

Early histopathology of small intestinal discordant xenografts.

A descriptive study of a new model enabling serial biopsies of ongoing hyperacute rejection of small intestinal discordant xenografts is presented. In a series of guinea-pig-to-Lewis rat small bowel xenotransplants (n=7), aboral free ends of Thierry-Vella loops constructed from the graft were sequentially biopsied at one-minute intervals up to ten minutes post-reperfusion and less frequently thereafter. In a guinea pig-to-guinea pig (n=6) isograft series, biopsy controls for preservation/ischemia-reperfusion injury were obtained. Xenoantibody sequestration in this model was evaluated in a separate series of transplants, utilizing an ELISA assay for rat anti-guinea pig natural antibodies. Pathologic evaluation revealed a unique series of events characterized with microcirculatory failure and thrombosis progressing from the submucosal vasculature to the lumen. Within the system's detection limits, complement deposition and P-selectin expression occurred as early as one minute post-reperfusion, preceding the staining for IgM and IgG. Using rat serum ELISAs, no significant difference in xenoantibody sequestration was detected between the xenograft and isograft groups. The guinea pig-to-rat discordant small bowel xenotransplantation is an efficient small animal model to dissect the very early pathophysiologic events during hyperacute rejection.

Central pontine myelinolysis and cyclosporine neurotoxicity following liver transplantation.

In a recent series of 44 liver transplants we identified both extrapontine myelinolysis (EPM) - characteristic of cyclosporine neurotoxicity - and central pontine myelinolysis (CPM) in 5 recipients posttransplant. An additional 2 recipients had EPM only posttransplant. MRIs performed in 4 asymptomatic recipients were normal. Large perioperative shifts in serum sodium, hypomagnesemia, and high cyclosporine levels may play a role in the development of these lesions, although the evidence from this study is inconclusive. In addition to supportive care, dilantin was started in patients who had seizures; aggressive magnesium replacement was initiated for hypomagnesemia, and cyclosporine levels were reduced in all patients. All patients demonstrated a slow steady recovery and all but 2 are at home at the time of writing. CPM may be more prevalent than previously appreciated following liver transplantation, although its prognosis may not be as dismal.

Synthetic peptides which inhibit the interaction between C1q and immunoglobulin and prolong xenograft survival.

BACKGROUND: Acute vascular xenograft rejection (AVXR), also termed delayed xenograft rejection (DXR), occurs when hyperacute rejection (HAR) is prevented by strategies directed at xenoreactive natural antibodies and/or complement activation. We have hypothesized that AVXR/DXR is initiated in part by early components of the complement cascade, notably C1q. We have developed synthetic peptides (termed CBP2 and WY) that interfere with the interaction between C1q and antibody. METHODS: CBP2 and the WY-conjugates were used as inhibitors of immunoglobulin aggregate binding to solid phase C1q. Inhibition of complement activation by the peptides of the classical system was determined using lysis assays with sensitized sheep red blood cells or porcine aortic endothelial cells as targets and of the alternate complement pathway using guinea pig red blood cells as targets. Two transplant models were used to study the effects of administering peptides to recipients: rat heart transplant to presensitized mouse, and guinea heart transplant to PVG C6-deficient rats. RESULTS: CBP2 and WY-conjugates inhibited immunoglobulin aggregate binding to C1q. The peptides also inhibited human complement-mediated lysis of sensitized sheep red blood cells and porcine aortic endothelial cells in a dose-dependent manner and the WY-conjugates prevented activation of the alternate complement pathway as shown by inhibition of guinea pig red blood cells lysis with human serum. In addition, the use of the peptides and conjugates resulted in significant prolongation of xenograft survival. CONCLUSIONS: The CBP2 and WY peptides exhibit the functional activity of inhibition of complement activation. These peptides also prolong xenograft survival and thus provide reagents for the study of the importance of C1q and other complement components in transplant rejection mechanisms.

A comparison of cyclosporine A and cyclosporine G in a rabbit heterotopic cardiac transplant model: graft outcome and histological findings.

Cervical heterotopic heart transplants were performed on 20 male New Zealand white rabbits comprising 4 treatment groups. Animals in each group were injected daily via the marginal ear vein and received one of the following regimes: Cyclosporine A, 10 mg/kg/day; Cyclosporine G, 15 mg/kg/day; cremophor-El, 3ml/day; or normal saline. Measurement of 24 hour trough blood concentrations revealed no significant differences between the average concentrations of Cyclosporine A and Cyclosporine G. Animals were examined daily and the cervical allografts assessed by palpation for viability/rejection. The duration of the study ended for each animal when the graft stopped beating at which time the animals were euthanized and the transplanted heart and native kidneys harvested and processed for light microscopy evaluation of rejection and drug toxicity, respectively. Graft survival in the Cyclosporine A group significantly surpassed that seen in the Cyclosporine G group as well as the control groups, whereas in animals treated with Cyclosporine G, graft survival was not different from controls. In the native kidney, there were no differences in glomerular tuft area or volume density amongst drug-treated or control animals. In contrast, tubule atrophy and interstitial fibrosis were markedly greater in Cyclosporine A-treated vs Cyclosporine G-treated animals. The results of this study indicate that, whereas Cyclosporine G is less nephrotoxic than Cyclosporine A, given equivalent blood concentrations Cyclosporine A delays rejection of a cardiac allograft significantly longer than Cyclosporine G in this animal species.

The emergence of xenotransplantation.

The field of transplantation is faced with a growing shortage of human organs as the list of potential recipients continues to increase. Those currently listed can already expect long waits; some die waiting. Xenotransplantation is a potential solution to this widening donor-recipient disparity. Consequently, in recent years, there have been several clinical attempts using organs from nonhuman primates and pigs. The results with nonhuman primates as donors have been encouraging, but it is unlikely that these species will provide a long-term solution to the organ shortage. Most recent xenotransplantation research has therefore shifted to more phylogenetically disparate species, such as pigs, as potential donors. The major barrier to transplantation between members of disparate species combinations has been hyperacute rejection (HAR). The elements of humoral immunity involved in this rejection process include (1) naturally occurring antibodies directed against carbohydrate and other antigens expressed on pig endothelium, and (2) the complement system, which is activated by binding of natural antibodies to their targets. Several elegant strategies to prevent HAR are being developed. The creation of transgenic pigs, whose cells express human regulators of complement activation, is one such strategy. Another promising approach has been to remove antidonor antibodies from the recipient by absorption with some recently characterized carbohydrate epitopes of porcine endothelial xenoantigens. Recent experimental work indicates that HAR can successfully be prevented by inhibition or depletion of complement. A delayed type of xenograft rejection, characterized by endothelial cell antibody deposition and cellular infiltration, occurs over the next three to four days. The likely mechanisms involved in delayed xenograft rejection include antibody-dependent cell-mediated cytotoxicity and the phenomenon of endothelial cell activation.

Simultaneous pancreas-kidney transplantation in the mycophenolate mofetil/tacrolimus era: evolution from induction therapy with bladder drainage to noninduction therapy with enteric drainage.

BACKGROUND: In the past, enteric drainage or the omission of induction immunotherapy has been shown to be predictive of suboptimal outcomes of simultaneous pancreas-kidney (SPK) transplantation. We have reassessed the need for bladder drainage and induction immunotherapy to optimize the outcome of SPK transplantation. METHODS: One hundred consecutive recipients of SPK transplants who received mycophenolate mofetil and tacrolimus immunosuppression were studied. The first 50 recipients had bladder-drained pancreas allografts and received induction immunotherapy. The results were compared with the next 50 recipients who had enteric-drained pancreas allografts, which included a subgroup (n = 17 patients) who were randomized to receive no induction immunotherapy. RESULTS: The 1-year actuarial patient, kidney, and pancreas survival rates in the bladder-drainage group were 98.0%, 94.0%, and 94.0%, respectively. The 1-year actuarial patient, kidney, and pancreas survival rates in the enteric-drainage group were 96.8%, 96.8%, and 89.4%, respectively. In the enteric-drainage group, the incidence of rejection at 1 year was 6.1% in recipients who received induction therapy versus 23.5% in recipients who did not receive induction therapy. The average number of readmissions per recipient was 1.8 in the bladder-drainage group versus 0.9 in the enteric-drainage group. CONCLUSIONS: Primary enteric drainage of the pancreas allograft in recipients of SPK transplantation is the preferred surgical technique in the tacrolimus/mycophenolate mofetil era.