3-OR

Abstract

Aim HLA-A2, B57 and B58 share a well-defined epitope (Ep) which corresponds to the 62GE eplet on the α1 helix, but not all antibodies (Ab) bind equally to these alleles (Al). Methods Six 62GE-specific human monoclonal antibodies (mAb) were tested in Luminex single Al assays with OneLambda (OL) and Gen-Probe (GP) kits according to manufacturer’s instructions. Both have A∗02:01/A∗02:03/B∗57:01/B∗58:01. Only OL has A∗02:06 and B∗57:03; only GP has A∗02:02 and A∗02:05. Results Three mAbs reacted well with all 62GE Al. MFI values were 16688 ± 3565(OL), 11843 ± 2993(GP); other Al had low MFI (range 4-89(OL), 2-211(GP)). Three mAbs had much lower MFI with 62GE Al: 7580 ± 3521(OL), 3107 ± 4228(GP). The table shows kit-related differences: [Fig. 1] For WK1D3 and VN2F1, A∗02:01 and ∗02:03 were OL-positive but GP-negative; note that A∗02:05(GP) reacted well. WIM1B3 reacted with all 62GE Al except B∗57:01(GP). Reactivity (Rx) patterns were reproducible upon repeat testing. Download : Download full-size image Conclusions Differences between Al Rx in OL and GP can be explained by the concept that peptides bound to the groove affect binding of some HLA Ep-specific Ab. Mulder et al demonstrated “peptide-dependent” HLA Ab (J. Immunol. 175:5950, 2005), anti-HLA-A2 mAb with binding differences to recombinant A∗02:01 molecules loaded with different peptides. Also, Rx of some mAb with mouse class I antigens has been shown to be governed by a limited peptide repertoire. The 62GE eplet and peptides in the groove are in close enough proximity to serve as additional Ab contact sites. Discrepancies between OL and GP Ab Rx patterns may reflect the possibility that Al preparations have different peptide profiles related to different vendor manufacturing processes.