*Purpose: To determine if mismatches in the SIRPα receptor, associated with initiate innate alloresponses in animal models, may impact human kidney transplantation outcome.

*Methods: To avoid confounding HLA mismatch factors, we choose a cohort of 55 consecutive kidney transplant recipients of an organ from an HLA-identical (ID) related donor. Biopsies were available for 47 patients. SIRPα typing was performed to identify the 2 most common alleles by PCR-SSP. Clinical information was obtained from medical records.

*Results: Mean follow up time was 4.6y (±2.6). 9 patients (pts) presented with slow graft function and 6 developed graft failure. TCMR and/or Borderline Changes (BC) on histology was seen in 17 and interstitial inflammation in 15 pts. No ABMR was detected. 2 pts died from unrelated causes. Most HLA-ID pairs were also identical for SIPRα typing: 15 pairs were typed as AA/AA (Donor/Recipient), 16 as AB/AB and 7 as BB/BB. Mismatched typings were found in 4 AA/AB, 4 AB/AA, 4 AB/BB, 3 BB/AB, 1 AA/BB and 1 BB/AA pairs. Transplant across AA/AA typing was associated with increased frequency of TCMR/BC compared with other SIRPα combinations (54% vs. 17%, p=0.03). We further analyzed the role of SIRPα in either donor or recipient, rather than the combination. Importantly, a significant increase in TCMR/BC and interstitial infiltrate was observed when the donor was typed as AA, compared with other donor types (50% vs. 13% p=0.016 and 56% vs. 19% p=0.025 respectively).

*Conclusions: The results of this small cohort of kidney recipients from HLA-identical, biologically related, donors suggests a role for innate immunity in transplant outcome. Further, our results indicate that donor SIRPα typing may have a significant role independent of recipient’s typing. Additional studies in HLA-ID and non-ID transplant recipients are required to corroborate these findings, which suggest that SIRPα typing may be used as a tool for risk stratification in kidney transplantation.

The authors thank Dr Jar-Haw Lee for typing reagents and technical support.

« Back to 2019 American Transplant Congress