Direct quantitative measurement of the kinetics of HLA-specific antibody interactions with isolated HLA proteins

All antibodies were characterized by fast on-rates and slow off rates but with a wide range of association rates (kon, 3.63-24.25 × 105 per mol per second) and dissociation rates (koff, 0.99-10.93 × 10−3 per second). Dissociation constants (KD) ranged from 5.9 × 10−10 M to 3.0 × 10−8 M. SN320G6 has approximately a twenty-fold greater affinity for HLA A2 compared with SN607D8, but has a similar affinity for HLA-A2 and B57. In contrast, SN607D8 has greater than a twofold greater affinity for HLA-A2 compared with A68. Similarly, WK1D12 has about a threefold greater affinity for HLA-B27 compared with B7. The higher affinity interactions correlate with the specificity of stimulating antigen. This is the first study to directly measure the binding kinetics and affinity constants for human alloantibodies against HLA.