Significance of qualitative and quantitative evaluations of anti‐HLA antibodies in kidney transplantation

Summary In this study, we retrospectively investigated the relationship between the presence/titers of donor‐specific (DSA)/nondonor‐specific antibody (NDSA) and the rate of graft rejection after transplantation. The subjects comprised 34 recipients who tested positive by FlowPRA ® Screening. The recipients were divided into two groups; 22 recipients with DSA and 12 recipients with NDSA, as detected using FlowPRA ® Single Antigen I and II beads. The antibodies were also quantitatively examined using the molecules of equivalent soluble fluorochrome (MESF) method. Nine of the 22 recipients with DSA (9/22, 40%) developed antibody‐mediated rejection (AMR), while none of the 12 recipients with NDSA (0/12, 0%) developed AMR ( P  < 0.01). In a quantitative analysis of the MESF data, patients with DSA with MESF values of over 3000 frequently showed AMR (8/11, 73%). In contrast, one of the patients with DSA with MESF values of <3000 showed AMR (1/11, 9%). One of the 12 patients (1/12, 8%) with NDSA showed cellular rejection (T‐cell‐mediated rejection), regardless of the MESF values. In patients with DSA, an MESF value of 3000 may be a useful cutoff value for identifying patients at a high risk for AMR.