*Purpose: Kidney transplants fail more often in African American (AA) than in Caucasian (CAU) recipients. We calculated the hydrophobic mismatch score (HMS) from polymorphic amino acids out of donor/recipient HLAs to select low immunogenic kidney transplants for African American patients.

*Methods: The HMS immunogenicity (IM) on a scale of 0-20 for 64,053 AA and CAU recipients was correlated with Kaplan-Meier survival estimates and Cox regression analyses.

*Results: The median kidney graft survival was 12.0 years in AA vs. 18.6 years in CAU recipients, a 6.6-year difference (p<0.001). Our analysis showed that AA recipients had higher both donor/recipient HLA-A/B/DR disparities and HMS IM values than CAU recipients (both p>0.001). We performed a re-matching simulation of 5,000 donor/recipient pairs with a priority for either 1,000 AA recipients or 4,000 CAU recipients. When 1,000 AA were matched first with 5,000 donors, 27.2% found HMS=0 donors, 44.5% HMS≤1.0 donors, and 66.5% HMS≤3.0 donors, all with an improved graft survival (Table 1). When CAU recipients were prioritized, AA patients found significantly less donors (Table 1). Importantly, preferential re-matching of AA recipients still allowed to accommodate the vast majority of CAU recipients: 35.8% with HMS=0 donors; 55.8% with HMS=2 donors and 74.6% with HMS=7 donors. Preferential CAU re-matching only slightly increased CAU re-matching, while dramatically decreased chances for AA recipients.

*Conclusions: Because higher HMS threshold is acceptable for CAU patients, the preferential AA matching significantly increased chances in finding low IM donors for AA recipients, but still providing excellent chances to find low IM donors for CAU recipients.

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