LAUSR

Luminex Single Antigen Beads Assay (SAB) are currently the most widely used means to identify HLA antibodies in sera from sensitized transplant candidates. Although these assays greatly enhance solid organ transplantation practices in terms of transplantig highly sensitized patients and the ability to perform virtual (electronic) crossmatch, issues concerning identifying unusual patterns or reactivity in some patients have emerged. This unusual pattern can be seen in male non-sensitized patients, patients with underlying auto-immune diseases, and normally sensitized patients. In order to investigate this pattern further, our lab utilized two primary testing platform. The One Lambda SAB Class I and Class II, was utilized as our primary testing patform. The LifeCodes SAB Class I and Class II was used as the secondary testing platform. Patterns of unusual reactivity were also examined by performing a flow cytometry crossmatch with surrogate donors. As control group, sera from 40 sensitized and non-sensitized patients were utilized to perfom the initial comparative study. Our results showed the HLA antibodies pattern of reactivity were identical between the two platforms. For patients with unusual HLA antibodies patterns, there was minimal correlation between the two platforms. False positive patterns identified by One Lambda SAB assays, were re-tested with LifeCodes SAB assays and results either in none or completely different false positive reactive patterns (see graph below). The absence of correlation between the two testing platforms in terms of false positive patterns might suggest that the patterns of reactivity might be directed to non-HLA IgG. In order to address that, we performed total IgG purification from two sera with this false positive pattern utilizing Protein A magnetic beads. SAB assay performed on purified IgG fraction eluted from the beads resulted in significant increase in the MFI values of these samples without any effect on the reactivity. In conclusion, interefence in SAB assays could be due to IgG fraction. Additional studies utilizing further blocking might be needed to eliminate this interfering patterns. Download : Download high-res image (237KB) Download : Download full-size image