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Background: Numerous studies have established the importance of innate immunity, particularly natural killer (NK) cells, in transplantation tolerance. NK cells express killer cell immunoglobulin-like receptors (KIRs) on their surface. By recognizing and binding major histocompatibility complex class I antigens, KIRs prevent autologous cell killing and promote lysis of non-self antigen-presenting cells. This study investigated the role of 16 KIR genes and donor-recipient KIR/HLA combinations on 5-year outcomes in a population of deceased donor kidney transplant recipients., Material/methods: We genotyped 126 renal transplant patients and their donors for HLA A, B, C, DR, and KIR genes. Patients underwent standardized transplantation and immunosuppressive protocols and were followed-up for 5 years. Graft function was evaluated by serum creatinine level and glomerular filtration rate calculated using the 4-variable modification of diet in renal disease (MDRD) equation., Results: The presence of KIR2DS3 in the recipients was associated with better graft function indexes over time (p<0.05), but this effect was not confirmed by multivariate analysis. Conversely, the presence KIR2DS3 in the recipients combined with the presence of its HLA ligand in the donor had a detrimental effect on the trends of serum creatinine levels and eGFR trends, also confirmed by multivariate analysis. Kidney transplant recipients negative for the KIR2DL1 gene displayed higher creatinine levels after 5 years. Lastly, transplantation of HLA-A3/A11-negative donor kidneys into KIR3DL2-positive patients exerted a protective effect in terms of 5-years outcome (p<0.05)., Conclusions: The present study demonstrates an important role of the KIR immunogenetic system in the long-term immune response to kidney transplantation.

Three hundred sixty-five patients who underwent cadaver donor kidney transplantation between 1993 and 1998 were divided into four groups: 40 immunized patients with at least one peak panel-reactive antibody (PRA) value more than 50%, 11 hyperimmunized patients with more than three peak PRA values over 50%, 10 retransplanted patients and 304 control patients. Before transplantation, we ascertained the antibody specificities against individual HLA antigens (Prastat Sangstat ELISA method for HLA typing of first donor, husbands of multiparous women and potential donors against whom candidates gave positive cross-matches); thus, patients underwent transplantation excluding the presence of the HLA antigens previously detected and looking for high HLA (class I and II) compatibility. Actuarial graft survival after 12 months was satisfactory in all groups: 87% immunized, 81% hyperimmunized and 80% retransplanted vs 92% controls. Renal function at the end of the first year was similar and the number of rejection episodes in the first 3 months did not significantly differ.

We report on a kidney transplant recipient experiencing an unexpected early acute vascular graft rejection. Retrospective analysis of patient serum samples, utilizing a new ELISA HLA screening technique, revealed that the rejection crisis and the subsequent graft loss were due to a pretransplant donor-specific pre-sensitization caused by a non-complement-fixing antibody of IgG2 class. The case illustrates the clinical significance of non-complement-fixing anti-HLA antibodies. In addition it is shown that ELISA methods are suitable for detecting potentially harmful donor pre-sensitization in waiting-list patients not detectable by standard lymphocytotoxicity techniques. Hence ELISA could be an alternative to flow cytometry for this purpose. It is concluded that screening and cross-matching techniques which detect non-complement-fixing anti-HLA antibodies could improve graft outcome, and should form part of the immunological monitoring of kidney transplant waiting-list patients.

Patient presensitization represents a considerable problem in candidacy for renal transplantation. While it is well known that hyperimmunized patients--panel reactive antibody (PRA) higher than 60%--create difficulties in donor matching and have a worse outcome than non-hyperimmunized patients, less information is available on patients with an intermediate degree of sensitization (30-60%). In order to evaluate how graft outcome relates to such degrees of sensitization, 241 consecutive transplanted patients were divided into two groups on the basis of their previous year's PRA peak: group A, PRA 0-29%; group B, PRA 30-60%. Group A showed a significantly better survival both in the first year (90% vs 79%, P < 0.05) and in the third year (82% vs 64%, P < 0.01). However, detailed analysis of group B demonstrated that some parameters may significantly influence graft outcome: (1) better compatibility on locus DR; (2) a primary kidney transplant; (3) a dialysis duration of less than 6 months; and (4) the prophylactic use of antilymphocyte globulin (ALG).

Flow cytometry (FC) may be considered as a fundamental technique in studying cell biology and pathology. It combines the quantitative character of biochemical methods with the multiparametric capacities of microscope analysis in a high-precision process for rapid analysis of individual cell characteristics. Three original FC techniques routinely applied in the field of renal transplantation are reported in the present study. They concern the donor-recipient cross-match test, the morphological analysis of urinary sediment and the modulation of the density of various membrane antigens on the lymphocyte surface. A common factor underlies all these methods: they aim to provide the physician with a reliable diagnostic tool in clinical renal transplantation.

The value of exfoliative urinary cytology for the diagnosis of different pathological conditions in renal transplantation is widely recognized. The method, however, has not yet gained full acceptance, mainly because identification of the different cells is not always possible by means of standard staining techniques. In view of its characteristics, flow cytometry (FC) seems to represent a consistently reliable, rapid and innovative approach for differentialing the various cells present in the urinary sediment and assessing their number. This study gives the examination result of 223 urinary specimens from 127 transplanted patients selected according to pathology. Sediment cells, collected from fresh urine samples, were washed, treated with a lysing solution, resuspended in saline solution and directly analysed in a FACSCAN cytometer. Morphological evaluation showed: a small number of cells in patients with stable renal function; a larger number of cells, with predominance of lymphocytes, during acute rejection episodes; an absolute predominance of neutrophils during bacterial infection; large-sized cellular debris in cases of post-transplant tubular necrosis; and small cell debris in cases of cyclosporine cytotoxicity. Lymphocyte surface-marker evaluation made it possible to differentiate lymphocyte populations observed during acute rejection episodes (cytotoxic T-cell, CD8 and HLA class II and NK cells) from those detected during bacterial infection (T-cell CD4 positive). These results suggest that urinary FC may be a reliable diagnostic tool in clinical renal transplantation.

This paper reports a 2-year experience of more than 5,000 cross-match tests for renal transplantation. Tests were performed by means of both standard light microscopy and an innovatory method based on flow cytometry, an up-to-date investigative technique for computerized analysis of individual cell characteristics. Flow cytometry allowed a better detection of weak positive reactions (false-negative cross-matches) than light microscopy, thus reducing the risk of selecting candidates with donor presensitization. Transplant clinical outcome supported the value of this original and advanced technological method.