Chronic survival after human renal homotransplantation. Lymphocyte-antigen matching, pathology and influence of thymectomy

Enhancing the Value of Histopathological Assessment of Allograft Biopsy Monitoring

Traditional histopathological allograft biopsy evaluation provides, within hours, diagnoses, prognostic information, and mechanistic insights into disease processes. However, proponents of an array of alternative monitoring platforms, broadly classified as "invasive" or "noninvasive" depending on whether allograft tissue is needed, question the value proposition of tissue histopathology. The authors explore the pros and cons of current analytical methods relative to the value of traditional and illustrate advancements of next-generation histopathological evaluation of tissue biopsies. We describe the continuing value of traditional histopathological tissue assessment and "next-generation pathology (NGP)," broadly defined as staining/labeling techniques coupled with digital imaging and automated image analysis. Noninvasive imaging and fluid (blood and urine) analyses promote low-risk, global organ assessment, and "molecular" data output, respectively; invasive alternatives promote objective, "mechanistic" insights by creating gene lists with variably increased/decreased expression compared with steady state/baseline. Proponents of alternative approaches contrast their preferred methods with traditional histopathology and: (1) fail to cite the main value of traditional and NGP-retention of spatial and inferred temporal context available for innumerable objective analyses and (2) belie an unfamiliarity with the impact of advances in imaging and software-guided analytics on emerging histopathology practices. Illustrative NGP examples demonstrate the value of multidimensional data that preserve tissue-based spatial and temporal contexts. We outline a path forward for clinical NGP implementation where "software-assisted sign-out" will enable pathologists to conduct objective analyses that can be incorporated into their final reports and improve patient care.

The Possible Role of Anti-Neu5Gc as an Obstacle in Xenotransplantation

Seventy to ninety percentage of preformed xenoreactive antibodies in human serum bind to the galactose-α(1,3)-galactose Gal epitope, and the creation of Gal knockout (KO) pigs has eliminated hyperacute rejection as a barrier to xenotransplantation. Now other glycan antigens are barriers to move ahead with xenotransplantation, and the N-glycolyl neuraminic acid, Neu5Gc (or Hanganutziu-Deicher antigen), is also a major pig xenoantigen. Humans have anti-Neu5Gc antibodies. Several data indicate a strong immunogenicity of Neu5Gc in humans that may contribute to an important part in antibody-dependent injury to pig xenografts. Pig islets express Neu5Gc, which reacted with diet-derived human antibodies and mice deleted for Neu5Gc reject pancreatic islets from wild-type counterpart. However, Neu5Gc positive heart were not rejected in Neu5Gc KO mice indicating that the role of Neu5Gc-specific antibodies has to be nuanced and depend of the graft situation parameters (organ/tissue, recipient, implication of other glycan antigens). Recently generated Gal/Neu5Gc KO pigs eliminate the expression of Gal and Neu5Gc, and improve the crossmatch of humans with the pig. This review summarizes the current and recent experimental and (pre)clinical data on the Neu5Gc immunogenicity and emphasize of the potential impact of anti-Neu5Gc antibodies in limiting xenotransplantation in humans.

Xenoantigen Deletion and Chemical Immunosuppression Can Prolong Renal Xenograft Survival

OBJECTIVE

Xenotransplantation using pig organs could end the donor organ shortage for transplantation, but humans have xenoreactive antibodies that cause early graft rejection. Genome editing can eliminate xenoantigens in donor pigs to minimize the impact of these xenoantibodies. Here we determine whether an improved cross-match and chemical immunosuppression could result in prolonged kidney xenograft survival in a pig-to-rhesus preclinical model.

METHODS

Double xenoantigen (Gal and Sda) knockout (DKO) pigs were created using CRISPR/Cas. Serum from rhesus monkeys (n = 43) was cross-matched with cells from the DKO pigs. Kidneys from the DKO pigs were transplanted into rhesus monkeys (n = 6) that had the least reactive cross-matches. The rhesus recipients were immunosuppressed with anti-CD4 and anti-CD8 T-cell depletion, anti-CD154, mycophenolic acid, and steroids.

RESULTS

Rhesus antibody binding to DKO cells is reduced, but all still have positive CDC and flow cross-match. Three grafts were rejected early at 5, 6, and 6 days. Longer survival was achieved in recipients with survival to 35, 100, and 435 days. Each of the 3 early graft losses was secondary to IgM antibody-mediated rejection. The 435-day graft loss occurred secondary to IgG antibody-mediated rejection.

CONCLUSIONS

Reducing xenoantigens in donor pigs and chemical immunosuppression can be used to achieve prolonged renal xenograft survival in a preclinical model, suggesting that if a negative cross-match can be obtained for humans then prolonged survival could be achieved.

Analysis of OPTN/UNOS registry suggests the number of HLA matches and not mismatches is a stronger independent predictor of kidney transplant survival

HLA matching and mismatching, while inversely related, are not exact opposites. Here we determined the independent effects of HLA matching and mismatching on outcomes in deceased donor kidney transplant recipients. The United Network for Organ Sharing database (1995-2012) was utilized and analyzed for delayed graft function, one-year acute rejection, and death-censored graft survival using combined multivariable models including HLA matching and mismatching. Sensitivity analyses were performed using the subgroup of deceased donor kidney transplant patients after 2003 with more uniform HLA nomenclature and resampling analyses using bootstrapping on complete data available from 96,236 recipients. Individually, both HLA matching and mismatching showed significant associations with graft survival. Adjusting the model to take into account both matching and mismatching simultaneously, the degree of HLA mismatching lost significance while matching continued to have a significant prediction for delayed graft function, the one-year acute rejection rate, and graft survival. Sensitivity analyses and bootstrapping showed similar results for all studied outcomes. Thus, analysis of this large cohort demonstrates the apparent greater association of HLA matching over HLA mismatching on both early allograft events as well as graft survival. Future analyses should preferentially utilize HLA matching as a covariate over mismatching for accurately reflecting impact on graft outcomes.

Steroid-free immunosuppression since 1999: 129 pediatric renal transplants with sustained graft and patient benefits

Despite early promising patient and graft outcomes with steroid-free (SF) immunosuppression in pediatric kidney transplant recipients, data on long-term safety and efficacy results are lacking. We present our single-center experience with 129 consecutive pediatric kidney transplant recipients on SF immunosuppression, with a mean follow-up of 5 years. Outcomes are compared against a matched cohort of 57 concurrent recipients treated with steroid-based (SB) immunosuppression. In the SF group, 87% of kidney recipients with functioning grafts remain corticosteroid-free. Actual intent-to-treat SF (ITT-SF) and still-on-protocol SF patient survivals are 96% and 96%, respectively, actual graft survivals for both groups are 93% and 96%, respectively and actual death-censored graft survivals for both groups are 97% and 99%, respectively. Unprecedented catch-up growth is observed in SF recipients below 12 years of age. Continued low rates of acute rejection, posttransplant diabetes mellitus (PTDM), hypertension and hyperlipidemia are seen in SF patients, with sustained benefits for graft function. In conclusion, extended enrollment and longer experience with SF immunosuppression for renal transplantation in low-risk children confirms protocol safety, continued benefits for growth and graft function, low acute rejection rates and reduced cardiovascular morbidity.

Chimerism and tolerance in transplantation

Studies in experimental models (1953-1956) demonstrated that acquired donor-specific allotolerance in immunologically immature or irradiated animals is strongly associated with donor leukocyte chimerism. Bone marrow transplantation in immune-deficient or cytoablated human recipients was a logical extension (1968). In contrast, clinical (1959) and then experimental organ transplantation was systematically accomplished in the apparent absence of leukocyte chimerism. Consequently, it was assumed for many years that success with organ and bone marrow transplantation involved fundamentally different mechanisms. With the discovery in 1992 of small numbers of donor leukocytes in the tissues or blood of long-surviving organ recipients (microchimerism), we concluded that organ engraftment was a form of leukocyte chimerism-dependent partial tolerance. In this initially controversial paradigm, alloengraftment after both kinds of transplantation is the product of a double immune reaction in which responses, each to the other, of coexisting donor and recipient immune systems results in variable reciprocal clonal exhaustion, followed by peripheral clonal deletion. It was proposed with Rolf Zinkernagel that the individual alloresponses are the equivalent of the MHC-restricted T cell recognition of, and host response to, intracellular parasites and that the mechanisms of immune responsiveness, or nonresponsiveness, are governed by the migration and localization of the respective antigens. Elucidation of the mechanisms of nonresponsiveness (clonal exhaustion-deletion and immune ignorance) and their regulation removed much of the historical mystique of transplantation. The insight was then applied to improve the timing and dosage of immunosuppression of current human transplant recipients.

Immunoglobulin-G subclass antidonor reactivity in transplant recipients

Outcomes may differ after kidney transplantation compared to combined liver-kidney transplantation. In animal models, distinct patterns of antidonor immunoglobulin (Ig) G subclasses are associated with either rejection or transplant tolerance. Flow cytometry has increased the sensitivity of antidonor immunoglobulin detection. We compared antidonor IgG subclass responses in kidney transplant recipients to those in recipients of liver or multiorgan grafts. In this study of 19 organ (kidney, liver, pancreas) transplantations, recipient serum incubated with donor splenocytes was tested by flow cytometry for the presence of IgM, IgG, or IgG subclass 1-4. Sera before transplantation and 10 days and 100 days after transplantation were used. No differences were seen in antidonor IgM, IgG, or IgG subclass antibodies among recipients of kidney transplants and liver grafts or combination grafts, either before or after transplantation. IgG4 gradually but significantly increased after transplantation in all groups. High levels of antidonor IgG3 either before transplantation or produced after it were found in 3 kidney recipients who experienced acute rejection. No other patients experienced rejection, and no other increase in IgG3 was seen. In conclusion, antidonor IgG subclass profiles may be useful to distinguish populations at risk of rejection but they do not differentiate the immunological response after kidney transplantation from that after liver or combined transplantation. A late rise in antidonor IgG4 is consistent with decreased antidonor reactivity thought to occur late after transplantation.

Protective anti-donor IgM production after crossmatch positive liver-kidney transplantation

The mechanism by which a liver transplantation might protect a simultaneous kidney transplant in a crossmatch-positive recipient is unknown. Flow cytometry crossmatch (FCXM) has increased the sensitivity of donor-specific antibody (DSA) detection compared with complement-dependant cytotoxicity (CDC). Here we compare the outcome of a liver-kidney transplantation (LKT), which was CDC and FCXM positive, to the mate-isolated kidney transplantation (KT), which was CDC negative but FCXM positive, from the same donor. Immunoglobulin G (IgG) and immunoglobulin M (IgM) DSAs were measured by FCXM using splenocytes and purified T cells. The KT graft was hyperacutely rejected and removed, but the LKT graft survived without episodes of rejection. Both the KT and the LKT recipients had high levels of circulating antidonor IgG, but not IgM, before transplantation. By day 3, antidonor IgG and IgM in the LKT recipient increased 2 and 7 fold respectively, whereas the KT recipient maintained the high IgG level but did not increase IgM. Histology of the KT graft showed IgG and complement (C1q) deposition, but in the LKT grafts, IgM was deposited without IgG or C1q. Circulating IgG and IgM DSAs returned to background by day 10 and were still at background on day 100. We report a crossmatch-positive LKT where posttransplantation production of IgM DSA, which failed to fix complement, appeared to protect the grafts.

History of clinical transplantation

The emergence of transplantation has seen the development of increasingly potent immunosuppressive agents, progressively better methods of tissue and organ preservation, refinements in histocompatibility matching, and numerous innovations in surgical techniques. Such efforts in combination ultimately made it possible to successfully engraft all of the organs and bone marrow cells in humans. At a more fundamental level, however, the transplantation enterprise hinged on two seminal turning points. The first was the recognition by Billingham, Brent, and Medawar in 1953 that it was possible to induce chimerism-associated neonatal tolerance deliberately. This discovery escalated over the next 15 years to the first successful bone marrow transplantations in humans in 1968. The second turning point was the demonstration during the early 1960s that canine and human organ allografts could self-induce tolerance with the aid of immunosuppression. By the end of 1962, however, it had been incorrectly concluded that turning points one and two involved different immune mechanisms. The error was not corrected until well into the 1990s. In this historical account, the vast literature that sprang up during the intervening 30 years has been summarized. Although admirably documenting empiric progress in clinical transplantation, its failure to explain organ allograft acceptance predestined organ recipients to lifetime immunosuppression and precluded fundamental changes in the treatment policies. After it was discovered in 1992 that long-surviving organ transplant recipients had persistent microchimerism, it was possible to see the mechanistic commonality of organ and bone marrow transplantation. A clarifying central principle of immunology could then be synthesized with which to guide efforts to induce tolerance systematically to human tissues and perhaps ultimately to xenografts.

HLA and cross-reactive antigen group matching for cadaver kidney allocation

BACKGROUND

Allocation of cadaver kidneys by graded human leukocyte antigen (HLA) compatibility scoring arguably has had little effect on overall survival while prejudicing the transplant candidacy of African-American and other hard to match populations. Consequently, matching has been proposed of deduced amino acid residues of the individual HLA molecules shared by cross-reactive antigen groups (CREGs). We have examined the circumstances under which compatibility with either method impacted graft survival.

METHODS

Using Cox proportional hazards regression modeling, we studied the relationship between levels of conventional HLA mismatch and other donor and recipient factors on primary cadaver kidney survival between 1981 and 1995 at the University of Pittsburgh (n=1,780) and in the United Network for Organ Sharing (UNOS) Scientific Registry during 1991-1995 (n=31,291). The results were compared with those obtained by the matching of amino acid residues that identified CREG-compatible cases with as many as four (but not five and six) HLA mismatches.

RESULTS

With more than one HLA mismatch (> 85% of patients in both series), most of the survival advantage of a zero mismatch was lost. None of the HLA loci were "weak." In the UNOS (but not Pittsburgh) category of one-HLA mismatch (n=1334), a subgroup of CREG-matched recipients (35.3%) had better graft survival than the remaining 64.7%, who were CREG-mismatched. There was no advantage of a CREG match in the two- to four-HLA incompatibility tiers. Better graft survival with tacrolimus was observed in both the Pittsburgh and UNOS series.

CONCLUSIONS

Obligatory national sharing of cadaver kidneys is justifiable only for zero-HLA-mismatched kidneys. The potential value of CREG matching observed in the one-HLA-mismatched recipients of the UNOS (but not the Pittsburgh) experience deserves further study.

Science, specialization, and the American Surgical Association

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Overview of the present and future of clinical transplantation

An historical overview of kidney transplantation including the rehabilitation status of long-term survivors, the ethical issues related to current American transplantation, and projections for the future are presented.

An analysis of cytomegalovirus infection and HLA antigen matching on the outcome of renal transplantation

Eighty-five recipients and donors of renal allografts were examined for evidence of cytomegalovirus infection before and repeatedly after transplantation. The recipients were also divided into two group on the basis of HLA antigen matching. Better allograft survival was noted in patients well matched for HLA antigens (0-2) mismatched antigens) compared to those poorly matched (three or more antigens mismatched), and in patients free of cytomegalovirus compared to those infected. Cytomegalovirus infection had a more marked influence on allograft survival than did HLA antigen matching. The differing rates of success of transplantation, apparently dependent on blood relationship between donor and recipient, have been assumed largely to be due to inherited factors. This study, however, revealed an important factor to be the disparate incidence of cytomegalovirus infection in sibling, parental, and cadaveric categories of transplantation. The mechanism of this disparity can be explained on the basis of the incidence of latent CMV infection in the recipients and various categories of kidney donors.

Factors in the differential rate of arteriosclerosis (AS) between long surviving renal transplant recipients and dialysis patients

In this study, the incidence of clinical and autopsy arteriosclerosis (AS) was studied in over 300 renal transplant patients (RTP) followed in our clinic up to 13 years post-transplant. Of 45 RTP followed a mean of 10.45 years, the incidence of clinical AS was 6% or 0.58% per year at risk. The incidence of death from AS was 2.2% over 10 years or 0.22% per year at risk. There was no apparent tendency for increase of the risk incidence with increasing time post-transplantation up to 13 years. This incidence of clinical and death-related AS in long term RTP contrasts sharply with a quite high incidence of both clinical and death-related AS in long-term dialysis patients as reported by Scribner's group and both the European and U.S. Dialysis Registry. Of our RTP surviving a decade or more, 77% have normal serum triglycerides and 92% are normotensive, again contrasting sharply with a 70-80% incidence of hyperlipidemia and a 60-80% incidence of hypertension in long-term dialysis patients. These studies suggest that the high rate of accelerated AS in dialysis patients is largely reversed by successful renal transplantation, probably due to a lowering of both blood pressure and hyperlipidemia in the long-term RT patients. Practically, these results suggest that the superior survival of transplant patients over dialysis patients already evident at 10 year mark will widen further during the second post-transplantation decade.

Gamma-glutamyl transpeptidase. A sensitive indicator of renal ischaemic injury in experimental animals and renal homograft rejection in man

The sites of ischaemic injury within the kidney are reviewed and the diagnostic value of measurements of plasma and urinary enzymes in renal ischaemic injury and in renal homotransplant rejection in experimental animals and man is examined. Gamma-glutamyl transpeptidase (gamma-GT) is an enzyme primarily located in the brush border of the proximal convoluted tubule of the kidney. Its unique localization in the cells most easily damaged by ischaemia and its ease of assay provide the rationale for its use in the measurement and diagnosis of renal ischaemic injury. gamma-GT activity was measured in dogs undergoing varying periods of renal ischaemia and under conditions of local renal hypothermia and was shown to be a sensitive indicator of ischaemic injury. Twenty consecutive patients undergoing renal homotransplantation were studied by daily estimation of their 24-h urinary gamma-GT activity; excellent correlation was obtained between raised levels of this enzyme and the clinical diagnosis of transplant rejection.

A decade followup in early cases of renal homotransplantation

Sixty-four consecutive patients underwent renal homotransplantation 10 1/6 to 11(1/2) years ago, 46 from related and 18 from nonrelated living donors. Thirty-six of these recipients were alive when this series was presented to the American Surgical Assocation in 1965. Now, nine years later, 26 (72%) of the 36 still survive, in 22 instances with function of their original grafts. The 10 who died in the interim tended to have subnormal renal function or graft failure. However, the actual causes of death included 2 or more examples each of myocardial infarction, hepatitis, or other systemic infections. The prognosis for achieving a one decade survival was not obviously related to HL-A tissue match. The best results were with related kidneys, within which subgroup 24 (52%) of the original recipients are still alive. However, there was no particular category of consanguineous donor that had a marked superiority. Only 2 of 18 nonrelated recipients are still alive. All 36 patients who were alive in 1965 had a biopsy of their renal homograft. Kidneys that were destined to function for a decade tended to have relatively minor histopathologic abnormalities. If serious glomerular lesions were found, the outlook for long graft survival was grave. Vascular lesions had a somewhat less serious import. Mononuclear cell infiltration, tubular atrophy, and interstitial fibrosis proved prognostically to be the least significant. Long-term followup of these early cases has shown the durability of chronic renal homografts, particularly if these are from related donors, and has demonstrated the very high degree of rehabilitation that could be achieved even in the early days of renal homotransplantation.

Variations in arterial blood pressure after kidney transplantation. Relation to renal function, plasma renin activity, and the dose of prednisone

The course of hypertension within the first 2 months after kidney transplantation was correlated with renal function, plasma renin activity (PRA), and the daily maintenance dose of prednisone in 18 homograft recipients. During acute rejection blood pressure (BP) closely correlated with PRA. Patients with normal homograft function showed an increase in BP early after transplantation which in most returned to normal 3–8 weeks later. In the latter group no correlation could be found between the level of BP and PRA, however the BP correlated closely with the dose of prednisone. These observations suggest that during acute rejection the increase in BP may at least partly be mediated by a renal pressor mechanism, whereas with normal renal function the high dose of glucocorticoids may play an important role in the development of hypertension.

Altered venules in the stimulated human thymus as evidence of lymphocyte recirculation

Human thymic tissue was examined by light microscopy to determine the presence or absence of germinal centres and plump venule endothelium. Five out of fifteen thymuses from control patients showed occasional germinal centres. A suggestion of plump venule endothelium was seen in only three of these. Among forty-one thymuses removed from patients with myasthenia gravis, thymoma, thymic enlargement or chronic renal failure nineteen contained definite germinal centres and of these fifteen showed plump venule endothelium. The evidence that this indicates a large scale recirculation of lymphocytes through the thymus has been reviewed.

Psychiatric aspects of renal homotransplantation

This paper describes some of the psychiatric aspects of the surgical transplantation programme at the Royal Melbourne Hospital Renal Unit. The stresses to which patients and their families are exposed and their methods of coping with them are considered. Various pathological reactions to stress are also described. The implications of these phenomena for a psychiatrist working with a Renal Unit are discussed.

Thymectomy and renal homotransplantation

The course of forty-six consecutive patients were studied for 3½–5 years after renal homotransplantation from related and unrelated donors. Transthoracic thymectomy was performed before transplantation in twenty-four cases; the other twenty-two recipients served as controls. A similar spectrum of donor-recipient lymphocyte antigen compatibility was present in both the test and control series.

In both the related and non-related cases, there was no clinical evidence that the patients with thymectomy had either an early or late advantage in terms of survival, reduced drug dosages, or quality of renal function. However, pathologic studies with light and electron microscopy and with immunofluorescence revealed that the homografts in the thymectomized patients had fewer and less severe lesions of the kind that would be expected to limit the functional life time of these organs.

Chronic renal homograft function: correlation with histology and lymphocyte antigen matching

Renal function was studied in twenty-nine of thirty-four surviving renal allograft recipients from an initial group of sixty-four patients two years after transplantation. Mean clearances of inulin and PAH were, respectively, greater than and equal to half the donors’ initial predicted clearances. Minimum urine osmolality during water diuresis was greater, and maximum urine osmolality during hydropenia was less than normal, an effect attributable partly to enhanced solute load in a single transplanted kidney.

Patients with compatible donor-recipient lymphocyte antigens demonstrated statistically better function than those with one or more incompatibilities, although there was a definite degree of overlap between the two groups. In contrast, little correlation could be demonstrated between the cumulative histopathology and renal clearances.

Renal function in patients with compatible donors was statistically greater than half the donors’ initial predicted function. Serial increase in renal clearances was documented in one patient with a compatible donor. Serial decreases were demonstrated in two patients with incompatible donors. These findings suggest that hypertrophy of the denervated, transplanted kidney occurs when immune reaction is minimal.