Effects of Different Sensitization Events on HLA Alloimmunization in Solid Organ Transplantation Patients

Intravenous human immunoglobulin treatment of serum from HLA-sensitized patients in kidney transplantation

OBJECTIVE

Intravenous immunoglobulin (IVIG) products are known to have beneficial immunomodulatory effects on several inflammatory and autoimmune disorders. These effects could be attributed to a different inhibitory action on complement factors, but other mechanisms could be implicated, e.g., immunocomplexes development and/or anti-idiotypic antibodies. Positive results on the reduction of anti-Human Leukocyte Antigens (HLA) antibodies in highly sensitized patients have also been found. The present study focuses on the effect of IVIG on the reduction of Panel Reactive Antibody level and crossmatch positivity in sensitized patients awaiting kidney transplantation.

METHODS

The study was performed adapting an in vitro assay on sensitized patients' sera in waiting list for kidney transplantation. Sera of twelve highly sensitized patients were evaluated for the cytotoxicity inhibition after 10% IVIG treatment.

RESULTS

A reduction of anti- HLA antibody levels was observed in 75% (9/12) of treated patients in vitro, while 25% (3/12) resulted unresponsiveness. Particularly, our data showed a significantly higher Panel Reactive Antibody reduction for T lymphocytes (p<0.010) than B lymphocytes (p<0.032).

CONCLUSIONS

In this study, we have used an in vitro assay to investigate susceptibility to desensitization with IVIG treatment of sensitized patient sera. These findings reveal that the variable effect of IVIG on reducing Panel Reactive Antibody in our immunized patients could be attributed to a different inhibitory action on complement, likely due to the type and the titre of anti-HLA antibodies.

Women and kidney transplantation

Kidney transplant is the best kidney replacement treatment for end-stage kidney disease. The first step in moving toward kidney transplantation is referral to a transplant center for transplant evaluation. Education of dialysis staff and health-care providers may help increase referrals for evaluation. Patient education has been shown to enhance patient completion of the evaluation process. Patients have difficulty asking others to donate a kidney, but this process can be improved with home and community education. Living donors are more likely to be women than men, especially spousal donors. Deceased donors are more likely to be males younger than 35 years of age. There is a slight decrease in the rate of transplantation of women as compared with men, although not statistically significant. Pretransplant development of anti-human leukocyte antigen antibodies is more common amongst women and can be a barrier to successful transplantation and may prolong the waiting time for transplant. The long-term management of cardiovascular risk factors, osteoporosis, and age-appropriate cancer screening need to be addressed with posttransplant recipients. Women have an overall increased patient and graft survival as compared with men after transplant.

Luminex(®) and its applications for solid organ transplantation, hematopoietic stem cell transplantation, and transfusion

SUMMARY

The detection of antibodies against the human leukocyte antigen (HLA) complex has become indispensable in every clinical practice. The development of solid-phase assays like the Luminex allows the standardized measurement of anti-HLA antibodies (HLAab) with high sensitivity, albeit the relevance for some clinical settings remains a matter of debate. In this review we aim to describe the principle of Luminex-based antibody detection, including two modifications that allow identifying solely complement-activating antibodies. We then describe three applications for Luminex: i) detection of HLAab preceding solid-organ transplantation and monitoring of donor-specific antibodies posttransplant as a risk factor for antibody-mediated rejection; ii) presence of HLAab in recipients as a risk for graft failure in hematopoietic stem cell transplantation, especially in haploidentical or mismatched transplantations; iii) role of HLAab in blood transfusion including refractory thrombocytopenia and selection of suitable platelet donors, transfusion-related lung injury after plasma transfusion, and immunization against HLA after red blood cell transfusion despite leukodepletion. Although the Luminex platform constitutes a potent technology for HLA antibody detection, some drawbacks require the well-educated analysis and interpretation of data in critical cases. In addition, Luminex has become an important tool to identify clinically relevant antibodies.

Comparision of anti-HLA antibodies of kidney transplant candidates with chronic renal failure by two different methods: Flow-PRA and Luminex PRA

OBJECTIVE

The aim of the study was to compare anti-HLA antibodies examined as panel-reactive antibody (PRA) in kidney transplant candidates with chronic renal failure (CRF) with the use of 2 methods: Flow-PRA and Luminex-PRA.

METHODS

CRF patients displaying class I PRA (n = 34) and/or class II PRA (n = 41) were tested by the 2 different methods from April 2012 to September 2012, using antigen-coated beads.

RESULTS

Eleven (32.3%) 34 patients tested for class I PRA were female and 23 (67.7%) male; 17 (41.5%) 41 patients tested for class II PRA were female and 24 (58.5%) male. Only 2 patients were preemptive, the others had been subjected to dialysis. The concordance ratio of class I PRA test results between Flow-PRA and Luminex PRA was 67.6%. Whereas 13 samples (38.2%) were positive by Flow-PRA, 22 (64.7%) were positive by Luminex-PRA. Two of the 3 patients not previously immunized were found to be positive only by Luminex PRA; 1 was noted to be positive only by Flow-PRA. Regarding class II PRA screening, the concordance between Flow-PRA and Luminex PRA was 70.7%. Whereas 14 (34.1%) samples were positive for Flow-PRA; 24 (58.5%) were positive for Luminex-PRA. The 2 patients not previously immunized were positive only in Luminex PRA.

CONCLUSIONS

We speculated that the reason for the low concordance ratios was due to the use of sera that had been previously found to be indeterminate in PRA tests. We also speculated that the low concordance ratios were due to the coating procedure for the beads, which may cause changes in antigenic epitopes and decrease concordance between Flow-PRA and Luminex-PRA.

Approach to kidney transplant in sensitized potential transplant recipients

More than one-third of patients on waiting lists for kidney transplant are sensitized. Most have previously formed donor-specific and non-donor-specific serum antibodies and/or positive crossmatch by complement-dependent cytotoxity and/or flow cytometry. Two categories of alloantibodies include antibodies against major histocompatibility complex human leukocyte antigen class 1 and class 2 and antibodies against minor histocompatibility complex. A current positive crossmatch is an absolute contraindication for transplant. Positive historical panel reactive antibody and/or donor-specific antibodies (human leukocyte antigen and minor histocompatibility complex), even in the absence of a historical positive crossmatch, are associated with an increased risk for allosensitization, antibodymediated rejection, and accelerated graft failure. Desensitization protocols are numerous, complex, and expensive. It is recommended to perform a systematic determination of historical and current panel reactive antibody, donor-specific antibodies (human leukocyte antigen and minor histocompatibility complex), and crossmatch by the most sensitive assays. The risk of sensitization may be estimated from the combined results of the crossmatch with the donor and those of the recipient's panel reactive antibody and donor-specific antibodies at baseline. The adoption of a scoring system for risk stratification may facilitate the task of organ allocation for sensitized patients. Recipients with an estimated sensitization risk ≥ high may be referred preferably to the national waiting priority list and informed about the financial and the medical risks that may incur with future transplant. Sensitized patients at high risk for antibody-mediated rejection may benefit from a structured monitoring process involving systematic and regular immunologic, histologic, and functional assessments of the graft after transplant. We recommend the adoption and regular updating of these approaches to ensure safe and appropriate therapeutic standards in these sensitized patients, in accordance with best clinical practice.