BACKGROUND:The incidence of cancer is increased after solid organ transplantation. Natural killer (NK) cells are key effectors of the tumor immune response. METHODS:We conducted a cross sectional multicentre matched case-control study including 42 kidney transplant recipients (KTRs) on diagnosis of cancer and 41 KTRs without cancer. Extensive phenotyping of NK cells populations and functional tests of NK cells were performed. RESULTS:Kidney transplant recipients with cancer had a higher incidence of acute rejection (P = 0.02) and cytomegalovirus (CMV) infection (P = 0.03) than controls. They had more lymphopenia than control KTRs (1020/mm3 +/- 32 vs 1218/mm3 +/- 34; P = 0.001) including a CD4+ lymphopenia (P = 0.01). Total CD3-/CD56+ NK cell counts were similar in both groups. However, KTRs with cancer had a lower frequency of the cytokine-enriched CD56bright NK cell subset (P = 0.001). The percentage of NK cells expressing NKp46 was decreased in KTRs with cancer (45% vs 53 %, P = 0.001). Furthermore, the ability of NK cells to degranulate CD107a+ cytolytic vesicles was reduced (11% vs 22%; P = 0.02), and the percentage of NK cells secreting IFN[gamma] was decreased (7.5% vs 28.8%; P = 0.01) in KTRs with cancer. CONCLUSIONS:These results reveal an imbalance between NK cell subpopulations and functional NK cell defects in KTRs at the diagnosis of malignancy, including a decreased expression of NKp46 and decreased numbers of NK cells producing INF[gamma]. This study highlights the role of NKp46, a major activating NK cell receptor, which could be considered as a potential marker during immunological follow-up of KTRs.

To characterize the immune defect of patients with end-stage renal disease (ESRD), we performed NK cell subset analysis in 66 patients with ESRD treated by hemodialysis (n = 59) or peritoneal dialysis (n = 7). Compared with healthy blood donors, patients undergoing chronic dialysis showed a profound decrease in NKG2D+ cells within both the CD8+ T cell (58% vs 67%, p = 0.03) and NK cell (39% vs 56%, p = 0.002) populations. CD56dim cells, which comprise the majority of NK cells in the periphery, were more affected in this regard than were CD56bright cells. Uremic serum could decrease NKG2D expression on NK cells from healthy donors. Among factors that could contribute to the decrease in NKG2D expression in ESRD patients, reactive oxygen species (ROS) play a major role. We found that catalase could reverse the effects of uremic serum on NKG2D expression (p < 0.001) and that ROS down-regulated NKG2D at the mRNA level and at the NK cell surface. Additionally, ESRD patients had both increased membrane-bound MHC class I-related chain A (MICA) on monocytes (p = 0.04) and increased soluble MICA (203 pg/ml vs 110 pg/ml; p < 0.001). Both ROS and uremic serum could significantly increase in vitro the expression of the NKG2D ligand MICA on the renal epithelial cell line HK-2. Taken together, these studies suggest for the first time that both low NKG2D expression and up-regulation of its ligand MICA are related to ROS production and may be involved in the immune deficiency of ESRD patients.

Background. Chronic allograft nephropathy is the main cause of long-term kidney graft loss. The plasminogen activator inhibitor type 1 (PAI-1) is a potential fibrogenic molecule whose secretion is regulated by several metabolic, inflammatory, and genetic factors. We aimed to determine whether PAI-1 secretion in renal transplant patients is correlated with the decline in renal function after transplantation. Methods. Renal transplant patients (145 male/71 female) were included in the study 1-27 years after transplantation (median of follow-up: 7.35 years). At inclusion, routine clinical and biological data were collected, the 4G/5G polymorphism of the recipient PAI-1 gene was determined, and the PAI-1 plasma level was measured. Results. The mean rate of decline in renal function was −4.26±0.30 ml/min/year. By multiple linear regression analysis, the rate of decline in renal function was significantly correlated with proteinuria (P =0.0176), occurrence of late acute rejection episodes (P =0.0001), and PAI-1 plasma level (P =0.0051). In addition, PAI-1 plasma level was also significantly correlated with body mass index (P =0.038), insulin (P <0.0001), platelet count (P <0.0001), and fibrinogen (P =0.024). The PAI-1 gene polymorphism tested did not influence the rate of decline in renal function after transplantation nor the plasma level of PAI-1 antigen. Conclusion. We conclude that PAI-1, whose secretion is determined in large part by metabolic and inflammatory factors, may be implicated in the rate of decline in renal function after transplantation.

62 Pathogenesis of post-transplant KS is still unknown despite recent reports of association with HHV8. In order to analyze KS risk factors and value of HHV8 detection among GCIF kidney transplant patients (TP) alive betwen 1996-1998, we retrospectively compared TP who had developed post transplant KS before january 1996 with 2 matched controls (C) for age, sex, transplant year and center. Before KS diagnosis or at same follow-up for C, we analyzed: ethnic origin; number of blood transfusions, grafts and rejection episodes; immunosuppressive regimen; tuberculosis, i.v. treated fungal, CMV or herpes infections; serological status for HIV 1-2, CMV, Hepatitis B and C, Herpes; blood cell count, renal function. We searched for HHV8 viremia by PCR at time of study (ts), HHV8 antibodies (Ab) before and after the graft. Sera were tested blindly using 2 indirect immunofluorescence assays (IFA) with 2 derived HHV8(+) EBV(-) cell lines and ELISA (recombinant protein encoded by HHV8 orf 65) confirmed by western blot. We then prospectively followed HHV8 detection within KS lesions, normal skin and peripheral blood mononuclear cells (PBMC) in TP with KS onset at ts. Among 30 TP with KS 21±34 months (M) after grafting, 24 were in remission, 1 had stable KS, 5 were lost from follow-up at ts. 9 other TP had KS onset at ts. After, conditional logistic regression analysis, TP geographic origin (OR=15.1, p<0.001), antiHbc Ab (OR=5.9, p<0.005), hemoglobin <12g/dl (OR=6.3, p<0.001), lymphocytes<750/mm3 (OR=9.0, p<0.05) were KS risk factors but not use of cyclosporine (OR=0.2, p<0.05). Stepwise logistic regression showed independant increased risk with African origin (OR=50.0, p<0.001) and initial use of polyclonal antilymphocytes sera (OR=11.3, p<0.05). HHV8 Ab were detected before graft in 100% of 5 KS vs 10% of 20 C(p<0.001); after graft, in 92% of 13 KS at 74±66 M vs 34% of 23 C at 87±58 M(p<0.01). At ts, HHV8 viremia was detected in 11% of 9 (1 stable, 8 remission) KS vs 0% of 13 C (ns). Prospective study detected HHV8 sequences in recipient's KS lesions (6/6), normal skin (3/5), PBMC (7/9) and HHV8 Ab in 88% of 6 KS at KS onset with negativation of viremia in 3/3 TP with clinical resolution. This first case-control analysis identifies KS risk factors. It suggests that HHV8 Ab detection before graft is predictive of KS and viremia is related to tumor burden and evolution.