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Extracellular vesicles (EVs) present in the urine are mainly released from cells of the nephron and can therefore provide information on kidney function. We here evaluated the presence of vesicles expressing the progenitor marker CD133 in the urine of normal subjects and of patients undergoing renal transplant. We found that EV expressing CD133 were present in the urine of normal subjects, but not of patients with end stage renal disease. The first day after transplant, urinary CD133+ EVs were present at low levels, to increase thereafter (at day 7). Urinary CD133(+) EVs significantly increased in patients with slow graft function in respect to those with early graft function. In patients with a severe pre-transplant vascular damage of the graft, CD133(+) EVs did not increase at day 7. At variance, the levels of EVs expressing the renal exosomal marker CD24 did not vary in the urine of patients with end stage renal disease or in transplanted patients in respect to controls. Sorted CD133(+) EVs were found to express glomerular and proximal tubular markers. These data indicate that urinary CD133(+) EVs are continuously released during the homeostatic turnover of the nephron and may provide information on its function or regenerative potential.

Context: The first national quality control (QC) program of histocompatibility serum testing was performed in Italy in 2002., Objective: To monitor the performance of HLA typing laboratories while meeting the accreditation requirements of the European Federation for Immunogenetics (EFI), which require HLA typing laboratories to participate in external QC of their crossmatch and antibody analyses., Design: The Turin Transplant Immunology Service was asked to organize a QC survey of 17 HLA typing laboratories in Italy. Each laboratory received 12 serum specimens and 6 blood samples and was required to perform 36 crossmatches and 12 serum antibody specificity determinations., Settings: Data of participating centers were compared to establish whether EFI requirements were satisfied., Results: In crossmatch analysis, the results of 32 of 36 crossmatches reached the 75% consensus target, with all the participating laboratories meeting the standards of the EFI. In antibody analysis, only 7 of 17 laboratories met the EFI standards., Conclusion: The first Italian QC program shows that the participating laboratories obtained consistent results in crossmatching, whereas the results were less satisfactory in the determination of serum antibody specificity, where consensus was reached only with monospecific sera and antibody-negative samples.