L. Klingman

Variations of the lymphocytotoxicity test. An evaluation of sensitivity and specificity.

Multiple variations of the basic lymphocytotoxicity test have been reported to increase test sensitivity. Although these modifications are used routinely in crossmatch tests, as required by federal regulation, there has been no methodical assessment of the relative sensitivities and specificities of these techniques, with the exception of the well-studied antiglobulin method. We have performed such a comparison and found that these modifications do not, uniformly, increase test sensitivity. We also observed that the effect of a technique modification on test sensitivity as measured by overall lymphocytotoxic antibody titer does not reflect, necessarily, the effect on HLA-specific antibody. It is widely believed that the antiglobulin method is the most sensitive of the lymphocytotoxicity techniques. We observed that while the antiglobulin method increased overall test sensitivity dramatically, we achieved a comparable level of sensitivity by either substituting B cells for T cells or doubling both the serum and the complement incubation times. However, no other technique modification detected as many HLA antibody specificities as did the antiglobulin method. The data presented here provide useful guidelines for selecting techniques for HLA typing, antibody screening, and cross-matching.

Bridge to transplant experience: Factors influencing survival to and after cardiac transplant

OBJECTIVE Balancing longer duration of mechanical circulatory support while awaiting functional recovery against the increased risk of adverse events with each day on support is difficult. Therefore, we investigated the complex interplay of duration of mechanical circulatory support and patient and device factors affecting survival on support, as well as survival after transplantation. METHODS From December 21, 1991, to July 1, 2006, mechanical circulatory support was used in 375 patients as a bridge to transplantation, with 262 surviving to transplant. Implantable pulsatile devices were used in 321 patients, continuous flow was used in 11 patients, a total artificial heart was used in 5 patients, external pulsatile devices were used in 34 patients, and extracorporeal membrane oxygenation was used in 68 patients. Two time-related models were developed: (1) a competing-risks multivariable model of death on mechanical circulatory support, with modulated renewal for each sequential support mode; and (2) a model of death after transplant in which patient factors and duration of mechanical circulatory support were investigated as risk factors. RESULTS Survival after initiating mechanical circulatory support, irrespective of transplantation, was 86% at 30 days, 55% at 5 years, and 41% at 10 years; survival was 94%, 74%, and 58% at the same time intervals, respectively, after transplantation in those surviving the procedure. Risk factors for death included longer, but not shorter, duration of mechanical circulatory support, use of multiple devices, global sensitization, and poor renal function. CONCLUSION Initiating mechanical circulatory support early with a single definitive device may improve survival to and after cardiac transplantation. Early transplant, which avoids infection, sensitization, and neurologic complications, may improve bridge and transplant survival.

HLA and MICA allosensitization patterns among patients supported by ventricular assist devices

BACKGROUND Ventricular assist devices (VADs) are increasingly being used as a bridge to transplantation and have been implicated as a risk factor for allosensitization to human leukocyte antigens (HLA). We investigate the association between VAD and allosensitization to human leukocyte antigens (HLA) and major-histocompatibility-complex (MHC) class I-related Chain A (MICA) antigens. METHODS We considered all patients who received a VAD at our institution between 2000 and 2009; 89 of them had pre-VAD and post-VAD (≤6 months after implant) HLA antibody screening. A control group of non-VAD heart transplant candidates was constructed with at least 2 pre-transplant panel-reactive antibody (PRA) tests within 8 months. Two controls were randomly selected/VAD patient matched for year (n = 178). Patients and controls with available sera from these time-points were tested by Luminex/flow PRA single-antigen beads and by MICA antibody Luminex single-antigen beads. Medical records were reviewed for comparison of pre-transplant immunologic risk factors and post-transplant outcomes between the 2 groups. RESULTS Compared with controls, VAD patients had greater Class I differences between peak and initial PRA (18% vs. 0%, p < 0.0001) and higher peak PRA (24% vs. 6%, p < 0.0001). The differences between the 2 groups in Class II were less pronounced than in Class I. Of patients who had single-antigen testing, VAD implantation was significantly associated with development of new HLA antibody specificities (Class I and/or Class II) post-VAD with an increase in calculated PRA (cPRA) post-VAD compared with controls (16% vs. 0%, p < 0.0001). This risk was still present after adjusting for age, gender, pre-VAD PRA, transfusion and duration of follow-up in a multivariate analysis (p < 0.0001 and 0.02, respectively). There were no differences in development of MICA antibodies between the 2 groups (14% in both). There was no significant difference in the incidence of pre-transplant positive T-cell crossmatch, pre-transplant donor-specific HLA antibodies, rejection episodes or graft survival between the 2 groups. CONCLUSION Our results suggest that VAD is associated with significant HLA allosensitization independent of common risk factors.

Combined liver-kidney transplants: allosensitization and recipient outcomes.

Background. A pretransplant positive crossmatch in combined liver kidney transplants (CLK) is not considered a contraindication based on the reported immunoprotection conferred by the liver allograft. However, antibody-mediated rejection of the kidney in CLK has been reported recently. This prompted our study to investigate the impact of presensitization on CLK recipient outcomes. Methods. We examined kidney allograft and patient survival by indication of sensitization using Scientific Registry of Transplant Recipients data on CLK performed from 1995 to 2008. We defined sensitization as panel reactive antibody (PRA) more than 10% or a positive T-cell crossmatch (TXM). Results. Among 2484 CLK recipients with available PRA or TXM information, 30% had positive TXM or PRA more than 10%. Among those with TXM information, 12% had a positive crossmatch (n=234). In univariate analyses, patient (P=0.002) and overall kidney graft survival (P=0.015) were significantly diminished among sensitized patients. Differences in patient survival translated to estimated half-lives of 10.3 years among nonsensitized recipients versus 7.8 years among sensitized recipients, In multivariable Cox models, allosensitization was independently associated with patient death (adjusted hazard ratio=1.22, 95% CI, 1.04–1.43) and overall kidney graft loss (adjusted hazard ratio=1.16, 95% CI, 1.00–1.36). Conclusions. These results suggest a negative impact of presensitization on patient and overall renal allograft survival in CLK. Accordingly, presensitization may need to be considered in risk stratification and clinical management of CLK.

Autolymphocytotoxins in Cardiac Transplantation: Serology, Significance, and Association with HLA-A1 and HLA-A3

The presence of an autolymphocytotoxin (ALCT) in any potential organ recipient, and particularly cardiac recipients who often receive procainamide, can easily be confused with human leukocyte antigen (HLA) antibodies when serum screening and donor cross matching are done unless autocross matching and appropriate absorptions are performed. This has been a routine procedure in our pretransplant serum testing for cardiac transplant candidates and has revealed five patients with an ALCT.

Primary Graft Dysfunction After Zero-Mismatch Kidney Transplantation Secondary to Early Biopsy-Proven Acute Cell-Mediated Rejection: Case Report

We report a case of primary renal allograft dysfunction and early acute cell-mediated rejection after a 12/12 HLA antigen zero-mismatch (0MM) transplant. The recipient was a 40-year-old white man who was highly allosensitized, with a calculated panel reactive antibody score of 100%. In posteroperative day 1 the recipient remained anuric and underwent dialysis because of hyperkalemia. Graft biopsy showed early acute cellular rejection, Banff grade 2B. No evidence of antibody-mediated rejection was observed. To our knowledge, this case is the 1st to report early cell-mediated rejection after 12/12 HLA antigen 0MM kidney transplantation. This case suggests that highly sensitized candidates are at high immunologic risk even in the context of 0MM kidney transplantation.