Liver Graft Allocation by Means of a New, Regionally Shared "Mixed" Model: The Experience in Lazio.

INTRODUCTION: Since 2013, the regional network of transplantation centers "LAZIO TRANSPLANT" have adopted a new, mixed system for the allocation of liver grafts. METHODS: The organs from donors aged <65 are assigned to patients with higher Model for End-stage Liver Disease (MELD) scores on a common regional waiting list, whereas those from donors aged >65 are allocated to patients with higher MELD scores on a specific local waiting list (LWL) at each center, on a rotational basis. RESULTS: The new mixed allocation model grants a more rational allocation of the "standard" organs to the patients with the actual worst MELD score in the entire region, avoiding the possibility that a patient in relatively better clinical condition might be transplanted before a more severely ill patient on another center's waiting list. Nonstandard organs, presenting slightly increased transplant risks, are still allocated on a rotational basis among the different transplant centers, ensuring them the possibility to select, on the basis of a global clinical risk evaluation, those patients in their LWL whose MELD score would not grant any possibility to compete for the "standard" organ allocation. CONCLUSIONS: The application of the new model had no negative impact on the overall number of transplants performed or on the global list-satisfaction percentages, but has slightly improved the cumulative mortality of the patients in the waiting list, granting to the clinically worst patients a prompt graft allocation, independent of the local center belonging.

The registry of brain deaths in quality control program: evaluation of potentiality of each hospital in Abruzzo and Molise regions.

Quality control procedures in donation and transplantation of organ and tissue, which were started in 2001, are aspects of the activity of Regional Centre for Transplantation. Over the years there has been a significant increase in the number of diagnosed brain deaths that is close to the figure reported in the international literature of 50/60 per million inhabitants (p.m.i). Misidentification of brain death is still the most important cause of loss of organs for transplantation; in fact in Italy, there are some regions that overcome this value, but there are other regions in which the number of brain death identified is still low. Abruzzo and Molise in 2003 achieved the highest registered brain deaths (61 p.m.i.); in 2004, 51; in 2005, 43; and the projection for 2006 is about around 50. For this study we collected data from five hospitals with a neurosurgical unit, which were representative of procurement activity in two regions, because they had identified the most brain deaths, 53/65 in 2005. The data were compared among hospitals and with the Spanish country data (1999-2003), which was avant-garde for the processing of organ donation and transplantation in Europe. Some useful indices to define the theoretical capacity of donation for each hospital (ability to identify brain death, the cause of donor loss) were evaluated for determining the efficacy of the procedure in organ procurement.

Living donor transplant: wider selection criteria.

The availability of cadaveric donor organs is insufficient for actual needs. The organ demand increases by 20% per year. Living donor transplant (LDT) may be a valid therapeutical alternative provided one uses proper criteria. LDT provides many advantages, like improved patient and organ survival, short waiting time, and the possibility to carefully plan the procedure. Potential risks include perioperative mortality and renal dysfunction in the kidney donor. At present, kidney LDTs in Italy represent 8% of the total, with an organ survival rate of 97% after 1 year (vs 93% for cadaveric transplants) and donors mortality rate of almost null. Most LDTs are performed from kinsmen. Presently, law no. 458, 26 June 1967, is in force in Italy for kidney LDT and law no. 453, 16 December 1999, for liver LDT. The foundations of LDT are, of course, the recipient's condition, the donor's motivation, and the altruism of the donation. It is desirable that in the future an increasing number of LDT be performed, supported by a careful, widespread health education regarding organ donation from living subjects and by the possibility to obtain insurance for the donor, which has been considered but never provided by actual laws.

Impact of donor-specific antibodies on chronic rejection occurrence and graft loss in renal transplantation: posttransplant analysis using flow cytometric techniques.

BACKGROUND: Improvements in immunosuppressive therapy have greatly reduced acute rejection (ARj) episodes, ensuring better short-term graft outcome, but have not modified long-term survival in renal transplantation. It is now well accepted that chronic rejection (CRj) can be determined by both immune and/or nonimmune mechanisms. The aim of this study was to evaluate the importance of the posttransplant humoral immune response towards mismatched HLA graft antigens in CRj occurrence and graft outcome. METHODS: Serum samples from 120 nonpresensitized renal transplant recipients were prospectively screened for 1 year after surgery by means of flow cytometry cross-match (FCXM) and FlowPRA beads (microbeads coated with purified HLA class I and class II antigens) assays. All transplants were followed-up for 2 years or until graft removal. RESULTS: FCXM monitoring identified donor-specific antibodies (DS-Abs) in 29 (24.2%) of 120 transplanted patients. Correlation with clinical data highlighted a higher incidence of ARj in DS-Abs-positive patients compared to negative patients (62% vs. 13%, P<0.00001). Furthermore, graft failure occurred more frequently among FCXM-positive patients than among negative patients (34% vs. 1%, P<0.00001). The deleterious effect of DS-Abs on graft function was confirmed by serum creatinine levels 2 years after transplantation. These were in fact higher in subjects producing DS-Abs than in subjects with only ARj (mean creatinine: 2.5+/-1.3 mg/dL vs.1.7+/-0.5 mg/dL, P=0.04). FlowPRA analysis of DS-Ab HLA specificity highlighted the presence of anti-HLA class I antibodies in 85% of FCXM-positive patients, who also presented with a higher incidence of HLA-B mismatches than FCXM-negative patients (1.23+/-0.66 vs. 0.92+/-0.59, P=0.02). CONCLUSIONS: Flow cytometric techniques are precious tools for investigating the activation of the humoral response against HLA antigens of the graft in renal transplantation. DS-Abs production has a worse impact on organ function and survival than ARj episodes. These findings represent further proof of the threat posed by DS-Abs on long-term graft function and draw attention to the need for a specific immunosuppressive therapy aimed at counteracting the different kinds of immune activation toward graft.

HLA class I residue mismatch and renal graft outcome.

Donor-recipient HLA matching was retrospectively evaluated in 111 cadaveric renal transplants using Takemoto's ten-residue model in which HLA class I antigens are clustered by crossreactive group (CREGs) on the basis of amino acid sequence homology and the sharing of a particular public epitope. The grade and type of HLA residue mismatching were correlated to posttransplant, class I donor-specific antibody production (monitored by flow cytometry crossmatch), rejection occurrence and clinical outcome during the 1st year posttransplant. In 52 patients with 0 mismatchings (MMs) we observed a low incidence of rejection (11.1%) and antibody production (11.1%) for 0 CREG MM grade, while 1 MM was enough to increase immune response against graft (rejection 35%; antibodies 30%). Moreover, a significant correlation was observed between Q144, E163, Q62 and L82/R82 epitopes and the incidence of acute rejection and antibody production ("immunogenic" residues) in patients grouped for a single residue mismatch.

The role of DRB1 amino acid residue differences on donor-specific antibody production and acute rejection after cadaveric renal transplant.

The correlation between DRB1 amino acid residue matching, post-transplant humoral response and acute rejection (ARj) episodes was analysed in 51 renal transplant donor-recipient pairs in order to determine new criteria for organ assignment based on the alloreactivity of the residue within the peptide binding groove. HLA class I and II compatibility was defined using serological and genomic techniques; a sequence-based typing (SBT) was used for a higher resolution of DRB1 alleles. Humoral response was monitored in the first post-transplant year using triple staining flow cytometric analysis of donor-specific antibodies (Abs). Our data showed that DRB1 residue compatibility was always correlated to the absence of ARj while the presence of one or more aminoacid differences was associated with a similar frequency of ARj. Analysis of the mismatched DRB1 amino acid residue localised in the beta-pleated sheet and the alpha-helix of the DRB 1 molecule revealed that the frequency of beta-pleated sheet residue mismatches (MMs) was higher in the ARj-positive than in the ARj-negative group. A significant increase in the alpha-helix residue MMs was observed in patients with anti-class II Ab production (p = 0.034). Furthermore, analysing in detail DRB 1 MMs at the level of single amino acid residue, we found that the frequency of the mismatches localized in codon 9 and codon 28 in the beta-pleated sheet, as well as in codon 57 in the alpha-helix, was higher in patients who experienced ARj; on the other hand, MMs in codon 58 of the alpha-helix were more frequently associated with anti-class II Ab production. The identification of the residues more involved in alloreactivity onset will make it possible to define the existence of "permissive" or immunogenic" allele combinations which could simplify and increase the chances of a successful transplant.

Kidney transplant monitoring by anti donor specific antibodies.

Donor-specific anti-HLA antibodies were studied by cytotoxicity crossmatching (CTXM) and flow cytometry crossmatching (FCXM) in 117 kidney transplant candidates; the same study was carried out in 33 cadaver-donor kidney recipients, during the first 3 post-transplant months, for which donor cells were available. Pre-transport evaluation showed that 82.9% of subjects were CTXM negative/FCXM negative, 6.8% of patients were positive in both tests, and 10.3% were CTXM negative/FCCM positive. Post-transplant monitoring for donor-specific antibodies (Abs-DS) showed that nine recipients (27.3%) were FCXM positive; six of them were IgG+ and three IgM+. In comparing these results with the clinical course, a significant association between FCXM IgG+ and rejection episodes was observed (P < 0.01).