The use of positive B cell flow cytometry crossmatch in predicting rejection among renal transplant recipients

Abstract

We performed retrospective flow cytometry crossmatch (FCXM) on 106 renal graft recipients who were transplanted based on current T cell negative serologic crossmatch. T and B cell FCXMs were performed on current and historical peak reactive post-transplant sera using 1024-channel flow cytometer and the shift in median channel fluorescence (SMCF) over the negative control was calculated. Cut-off values for a positive T and B crossmatch, > 40 and > 80 SMCF, respectively, were determined based on previous retrospective analysis of the data in the context of clinical outcome in our center, and were 1.5 times the standard deviation (SD) above the mean median channel fluorescence (MCF) of normal sera controls. The 1-yr graft survival was 95% for the total group of patients studied, and 87% for the recipients who had a positive T cell FCXM. To focus on the influence of a positive B cell FCXM on the incidence of rejection, primary transplant recipients who had a negative T cell FCXM (n = 81) were studied. Fifteen of 30 (50%) recipients with a positive B cell FCXM experienced at least one rejection episode within the first year. By contrast, only 15 of 51 (29.4%) of patients with a negative B cell FCXM experienced rejection (p = 0.05). The mean B cell SMCF in the group of patients who had no rejections was 45 +/- 59, while that of the group of patients who experienced at least one rejection was 97 +/- 97 (p = 0.012). By comparison, the rejection rate among the retransplant patients was 44.4%, and the mean B cell SMCF in the group with rejection was 94 +/- 75 while it was 5 +/- 7 among retransplant patients who did not have rejection (p = 0.031). Eighty-six percent of sensitized (panel reactivity antibodies (PRA) > 10%) patients who had a B positive/T negative FCXM experienced rejection, compared to 33% (n = 6 out of 16) of the B negative/T negative sensitized patients (p = 0.03). Furthermore, 62% (n = 13 out of 21) of donor-recipient mismatched patients with a B positive/T negative FCXM experienced rejection, compared to 38% (n = 13 out of 35) of patients with T negative/B negative FCXM who were similarly mismatched (p = 0.064). These data demonstrate the value of a positive B cell FCXM for predicting post-transplant rejections particularly when evaluated in the context of prior sensitization and/or DR mismatching. Our results suggest that B cell FCXM may have significant clinical implications, justifying its use in post-transplant management of recipients who have other risk factors of rejection.

Enhanced De Novo Alloantibody and Antibody-Mediated Injury in Rhesus Macaques

“…Cells were stained with FITC-labeled anti-monkey IgG (KPL, Inc. Gaithersburg, MD), PE CD20 (BD Pharmingen, San Diego, CA), and PerCP CD3 (BD Pharmingen, San Diego, CA). The threshold for alloantibody positivity varies widely across literature, ranging from a 10–100 shift in mean fluorescence intensity for both CD3+ and CD20+ cells (15, 40–43); thus, in this study, a two-fold increase in mean fluorescence intensity from pre-transplant values was used to determine alloantibody positivity, with all positive shifts being greater than 100 shift in mean fluorescence intensity.…”

Human leukocyte antigens DR and AB and kidney retransplantation

“…Flow-positive B-cell crossmatches have been associated with poor retransplant survival (13)(14)(15)(16), even when the T-cell crossmatch is negative (15,16). Furthermore, Fuller et al (17) noted that only 3 of 13 (18%) serum samples from kidney recipients who were not mismatched for DR contained flowbead B-cell antibodies, in contrast with 17 of 22 (77%) serum samples that did contain antibodies from DR mismatched patients.…”

Efficacy of a Negative Conversion Trial and Subsequent Living Donor Kidney Transplant Outcome in Recipients with a Positive Lymphocyte Crossmatch

“…However, the clinical relevance of a positive B-cell crossmatch remains controversial. A positive B-cell crossmatch was not necessarily found to be detrimental to the outcome in some reports [15,16,17,18,19], while other groups have reported a detrimental impact on kidney graft outcome [20,21,22,23]. This discrepancy is probably due to the failure to discriminate whether the B-cell reactivity could be attributed to IgG or IgM antibodies in patient serum.…”