23-P

Abstract

Aim HLA-Cw antigens are expressed at lower levels on the cell surface when compared to other HLA antigens (McCutcheon 1995). Therefore, using the same MFI cut-off for HLA-Cw antigens as for the other HLA antigens to determine unacceptables may be negatively impacting some patients’ opportunity for transplantation. Methods Patient’s sera with reported anti-HLA-Cw- antibodies by Luminex Single Antigen Beads (One Lambda) were gathered and surrogate donor cells expressing known Cw-locus antigens were selected. The patients’ sera had ONLY donor specific antibodies to anti-HLA-Cw (DSA-Cw) and the MFI ranged from 1,180 to 21,008 MFI values. 43 patient-donor pairs have been tested and a total of 61 Flow T-Cell XMs (FT-XM) performed. Positive FT-XMs were run by serology AHG T-Cell XM (AHGT-XM). Results Our results showed that only 15% of the sera with DSA-Cw 7,500 MFI were POSITIVE. In total we had 25 FT positive XMs that were further analyzed by AHGT-XM. By serology, 100% of the sera with DSA-Cw 7,500 MFI were POSITIVE. Recently, it has being described that HLA-Cw alleles have different levels of expression and that this difference plays a role in controlling HIV progression (Thomas 2009; Kulkarni 2011). Therefore, we studied if this variation in the level of HLA-Cw expression also had a predictive value for FT-XM outcomes. We organized our FT-XM results depending on the DSA-Cw being a “high” or “low” expressed allele (Kulkarni 2011). Our results did not detect any significant difference, although more data is needed due to the small sample size. Conclusions This study suggests that raising the cut-off for HLA-Cw locus antibodies could give patients more organ offers than they are currently receiving. Based on our findings, our lab has raised the HLA-Cw cut-off from 1,500 to 7,500 MFI for one of the kidney transplant programs for which we provide service.