We analyzed the role of preformed a-MICA antibodies (Abs) in kidney recipients (n=727), transplanted between 2005 and 2011. Fifty two patients (pts) had preformed a-MICA Abs (7%). There were no differences in donor and recipient sex, HLA mismatches, PRA, treatments, CMV serology and primary nephropathy between MICA- and MICA+ pts. Distribution of MICA+ pts into HLA+ (4%) or HLA- groups (3%) and MICA- pts into HLA+ (23%) or HLA- groups (70%) did not show difference (p=0.08). A-MICA Abs and classical a-HLA sensitization events, such as previous transplants (tx) (p=0.35) or recipient female sex (potential pregnancies) (p=0.29) were not associated. We explored the role of preformed a-MICA Abs independently from a-HLA status by classifying pts into four groups, either according to Luminex-recorded a-HLA and a-MICA Abs, or to % PRA and Luminex-a-MICA Abs. In the 24 months period, biopsy-proven allograft rejection was superior in PRA+MICA- vs PRA-MICA- pts (17% vs 7%, p=0.007). Rejection increased after month 12 in PRA+MICA- pts, but was higher early postx in PRA+MICA+ pts, with significant global comparison (p=0.033). Rejection rates differences in pairwise comparisons were highest in PRA+MICA+ vs PRA-MICA- pts at 3 month (14% vs 2%, p=0.009), and also observed at 6 months (14% vs 2%, p=0.035). Allograft survival showed also global significant differences (p=0.042), mostly due to pronounced survival decreased in PRA+MICA+ pts early postx.

Multivariate analysis showed that HLA-MICA+ status at 3 months independently conferred the highest risk for rejection (OR: 5.07, p=0.049). As repeatedly reported, PRA > 0% and 4-6 HLA mismatches were independent risk factors for allograft rejection (OR=2.73 and p=0.006; OR= 2.41 and p=0.021 respectively), further reinforcing our finding on the role of preformed a-MICA Abs.

In conclusion, MICA and HLA pretx sensitization are independent and preformed a-MICA Abs increase risk for kidney rejection in the first months postx.

« Back to 2013 American Transplant Congress