Vascular rejection post heart transplantation is associated with positive flow cytometric cross-matching

Objective: Use of flow cytometry cross-matching for measurement of donor-specific alloreactivity and monitoring anti-donor antibodies is well established. This study was performed to determine (1) its accuracy as a marker of vascular rejection, (2) its correlation with post-transplant outcome and (3) its ability to monitor highly sensitized patients requiring antibody removal with plasma exchange. Methods: Serial serum samples from 99 heart transplant recipients were examined for the presence of anti-donor antibodies of the IgG class that were reactive with T and/or B cryopreserved donor lymphocytes. A sub-group of 20 HLA sensitized patients required plasma exchange to remove the anti-HLA antibodies and were monitored with flow cytometry cross-matching to assess the degree of antibody removal. Results: Positive T-cell reactions were observed in 26 patients and positive B-cell reactions in 54. Twenty patients had vascular rejection. A significantly larger number of patients with a positive flow cytometry cross-match had vascular rejection (42% versus 12% for T-cell reactions, and 32% versus 7% for B-cell reactions; P=0.002 each). Of the patients who had vascular rejection, 11 had a positive T-cell reaction (flow cytometry cross-match sensitivity of 55%), and 17 had a positive B-cell reaction (sensitivity of 85%). Of the 79 patients who did not develop vascular rejection, 64 had a negative T-cell reaction (specificity of 81%), and 42 had a negative B-cell reaction (specificity of 53%). The actuarial 2-year survival estimates were significantly higher in patients with negative T-cell reactions (90% versus 75%; P=0.04), and B-cell reactions (95% versus 78%; P=0.02). In the highly sensitized subgroup (n=20) the effectiveness of plasma exchange to decrease anti-HLA antibody reactivity was a strong predictor of outcome. For patients in whom plasma exchange (PE) reduced anti-donor reactivity, 1-year survival was 87% compared to 25% in those whom PE did not reduce the level of antibody binding as assessed with flow cytometry cross-matching (P