Artificially Positive Crossmatches Not Leading to the Refusal of Kidney Donations due to the Usage of Adequate Diagnostic Tools

Abstract

Allografting patients with human leukocyte antigens (HLA) which are recognized by preformed antibodies constitutes the main cause for hyper-acute or acute rejections. In order to select recipients without these donor-specific antibodies, the complement-dependent cytotoxicity crossmatch (CDC-CM) assay was developed as a standard procedure about forty years ago. The negative outcome of pretransplant crossmatching represents the most important requirement for a successful kidney graft survival. The artificially positive outcomes of CDC-based crossmatches due to the underlying disease Systemic Lupus Erythematosus (SLE), however, may lead to the unjustified refusal of adequate kidney grafts. Two prospective female recipients destined for a living as well as for a cadaver kidney donation, respectively, exhibited positive CDC-based crossmatch outcomes although for both patients no historical immunizing events were known. Furthermore, solid phase-based screening or antibody differentiation analyses never led to positive results. Immediate reruns of the CDC-based crossmatch assays using the alternative antibody monitoring system (AMS-)crossmatch ELISA resulted in unequivocally negative outcomes. Consequently both transplantations were performed without any immunological complications for the hitherto follow-up time of 25 and 28 months, respectively. We here show two case reports demonstrating an alternative methodical approach to circumvent CDC-based artefacts and point to the urgent need to substitute the CDC-based crossmatch procedure at least for special groups of patients.

Improved flow cytometry crossmatching in kidney transplantation

“…A study of women with systemic lupus erythematosus described two positive CDC-XM (for B-cells in the first case and for both T-and B-cells in the second case), although DSAs were not detected in a single antigen bead assay. 22 The lack of HLA specificity in these positive crossmatches was confirmed by (a) a negative ELISA-XM using HLA antigens from a donor cell lysate, and (b) the favorable outcome of transplantation at 2 years. It is noteworthy that the auto-Abs related to autoimmune disease leading to a false-positive CDC-XM during may correspond to complement-fixing IgGs, rather than IgMs.…”

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“…A study of women with systemic lupus erythematosus described 2 positive CDC crossmatches (for B cells in the first case and for both T and B cells in the second), even though DSAs were not detected in an SAFB assay. 23 The lack of HLA specificity in these positive crossmatches was confirmed by (1) a negative ELISA-XM using HLA antigen from a donor cell lysate and (2) the favorable outcome of transplant at 2 years. It is noteworthy that the autoantibodies leading to a false-positive CDC-XM during autoimmune disease may correspond to complement-binding IgGs rather than IgMs.…”

Role of crossmatch testing when Luminex-SAB is negative in renal transplantation

“…In the case of positive results, the presence of DSA is better determined by more specific means such as the Luminex and flow crossmatch assays (23). However, B-cell crossmatching has many limitations as it detects only complement-activating isotypes of antibodies, requires a high degree of vital donor cells, and may show false positive results due to autoantibodies present in patients with autoimmune diseases (24,25,26).In the United Network of Sharing (UNOS) registry, 55% of CDCXM-positive transplant cases were FCXM--negative (27). The present case, with a positive CDCXM and a negative FCXM, could be explained by a false positive CDCXM, a false negative FCXM, or by IgM as the responsible antibody.…”