Clinical and morphological practices in the diagnosis of transplant-associated microangiopathy: a study on behalf of Transplant Complications Working Party of the EBMT.

Transplant-associated thrombotic microangiopathy (TA-TMA) is a life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT). This study evaluated clinical and morphological practices of TA-TMA diagnosis in EBMT centers. Two questionnaires, one for transplant physician and one for morphologist, and also a set of electronic blood slides from 10 patients with TA-TMA and 10 control patients with various erythrocyte abnormalities, were implemented for evaluation. Seventeen EBMT centers participated in the study. Regarding criteria used for TA-TMA diagnosis, centers reported as follows: 41% of centers used the International Working Group (IWG) criteria, 41% used "overall TA-TMA" criteria and 18% used physician's decision. The threshold of schistocytes to establish TA-TMA diagnosis in the participating centers was significantly associated with morphological results of test cases evaluations (p = 0.002). The mean number of schistocytes reported from blood slide analyses were 4.3 ± 4.5% for TA-TMA cases (range 0-19.6%, coefficient of variation (CV) 0.7) and 1.3 ± 1.6% for control cases (range 0-8.3%, CV 0.8). Half of the centers reported schistocyte levels below 4% for 7/10 TA-TMA cases. The intracenter variability was low, indicating differences in the institutional practices of morphological evaluation. In conclusion, the survey identified the need for the standardization of TA-TMA morphological diagnosis.

Activated protein C reduces graft neutrophil activation in clinical renal transplantation.

We studied the role of endogenous activated protein C (APC), the major physiological anti-coagulant with concomitant anti-inflammatory properties, on ischemia/reperfusion (I/R) in 45 patients participating in a larger trial comparing three immunosuppressive protocols in cadaveric renal transplantation: perioperative anti-thymocyte globulin (ATG, Fresenius AG, Bad Homburg, Germany), perioperative basiliximab and conventional triple therapy. Blood samples for assessing plasma APC, protein C, and lactoferrin concentrations, neutrophil CD11b and L-selectin expressions and blood leukocyte differential counts were obtained preoperatively and before reperfusion from central venous cannula, complemented with simultaneous samples from iliac artery and graft vein for calculation of transrenal differences (Delta) of study parameters at 1 and 5 min after reperfusion. Unlike basiliximab or conventional therapy groups, ATG infusion induced a substantial increase in plasma APC concentration (119 [88-144]% before infusion vs. 232 [85-1246]% after infusion, p<0.001), resulting in renal graft sequestration of APC at 1 min after reperfusion (Delta=-72 [-567 to 12]%, p<0.001). Graft APC consumption was associated with transrenal reduction of neutrophil activation markers (L-selectin r=0.7, p=0.01; lactoferrin r=-0.6, p=0.02; CD11b r=-0.8, p=0.001), and with both warm (r=0.6, p=0.01) and cold ischemia time (r=0.6, p=0.02) and donor age (r=0.6, p=0.01). These findings suggest that APC has an anti-inflammatory role in I/R injury in clinical renal transplantation.

Association of graft neutrophil sequestration with delayed graft function in clinical renal transplantation.

BACKGROUND: The authors studied the impact of neutrophil activation, detected in experimental models, on reperfusion injury in clinical renal transplantation. METHODS: Forty-five patients from a larger trial comparing three immunosuppressive protocols were recruited: perioperative antithymocyte globulin (ATG) with low initial cyclosporine A (CsA) triple therapy (group A, n=15); two-dose basiliximab with low initial CsA triple therapy (group B, n=16); and conventional triple therapy (group C, n=14). Blood samples were obtained preoperatively, before reperfusion, and at 1 and 5 min after reperfusion. During reperfusion, samples were collected from the iliac artery and the graft vein for calculation of transrenal differences (Delta) of study parameters. Leukocyte differential counts, plasma lactoferrin concentration, and neutrophil CD11b and L-selectin expressions were assessed. Graft blood flow was measured at 2 and 30 min after reperfusion. RESULTS: ATG induced neutrophil activation already before reperfusion. Thus, group A was excluded, but groups B and C were pooled for analysis of reperfusion-induced neutrophil activation. At 1 min after reperfusion, lactoferrin concentration was higher in graft vein than iliac artery, yielding Delta=15 microg/L (P<0.05). Concomitantly, Delta neutrophil count correlated with both Delta L-selectin expression (R=0.49, P=0.012) and graft blood flow at 2 min (R=0.51, P=0.007). At 5 min after reperfusion, 0.17 (-1.0-0.24)x10 cells/L neutrophils were sequestered in the graft (P<0.001). This sequestration correlated with graft blood flow at 30 min (R=0.53, P=0.005) and was stronger in patients with delayed graft function (DGF) (Delta = -0.38 [-1.45 to -0.2]) than those without (Delta = -0.12 [-0.41-0.24], P<0.001). In multiple regression analysis, sequestration was the most important parameter associated with DGF. CONCLUSIONS: Neutrophils are activated and sequestered in the reperfused graft during clinical renal transplantation. Neutrophil sequestration is a powerful independent factor explaining the incidence of DGF.