*Purpose: Contribution of NK cells to antibody-mediated rejection (ABMR) injuries have recently been highlighted through transcriptomic analysis and immunohistochemistry of kidney and heart allograft biopsies. However, till date there are no available data to corroborate these findings with blood circulating NK cells profiles in ABMR.

*Methods: Here we aimed for a comprehensive examination of the phenotype of circulating CD56^brightCD16^dim and CD56^dimCD16^bright NK cells gated out of CD3-CD19-CD14-CD7+ using 25 color spectral flow cytometry in 9 kidney transplant (KTx) recipients: (i) donor specific anti-HLA antibody free of ABMR (DSA+ABMR-), (ii) DSA+ biopsy-proven ABMR (DSA+ABMR+), (iii) stable patients (DSA-) and (iv) 6 healthy controls (HC), the cohort currently being enlarged. Cross-sectional samples were analyzed at the time of first DSA detection or of ABMR occurring in the 3 first months post-KTx.

*Results: Overall, NK cells from KTx patients undergoing DSA+ABMR+ significantly proliferated according to Ki67 staining (62±30.3% in DSA+ABMR+, 30.6±14.1% in DSA+ABMR-, 18.2±2.7% in DSA-, 4.5±1.3% in HC, p=0.024). Interestingly, the upstream transcriptional regulator TCF7 uniquely expressed by CD56^brightCD16^dim from HC was decreased in all patients except for DSA+ABMR+ patients, who maintained its levels’ elevated. Moreover, de novo TCF7 expression was detected in the CD56^dimCD16^bright subset from DSA+ABMR+ patients (26.9±14.7% in DSA+ABMR+ vs 2.5±1.9% DSA+ABMR- vs 3.6±1.2% DSA- vs 8.2±9.4% in HC, p=0.05), subset that also selectively up-regulated IL-21R and IL-2/-15Rβ, thus supporting its possible self-renewal capacity, responsiveness to common γc cytokines and long-term persistence. In DSA+ABMR+ patients, unlike for the other groups, the CD56^dimCD16^bright NK subset co-expressed significant elevated levels of the Th1-promoting transcription factors EOMES (p=0.023) and T-bet, of the chemokine receptor CXCR3 (p=0.001), as well as of the activation NKG2D (p=0.007) and of the CD16a-inducible and cytotoxicity CD160 (p=0.017) markers, suggesting their activation status, potential for migration towards inflamed tissues and enhanced cytotoxicity via CD16.

*Conclusions: In conclusion, here we have identified significant NK cell phenotypic changes within CD56^dimCD16^bright subset during ABMR, with potential functional consequences to allograft injury. Early detection of proliferating, activated, cytotoxic, and with self-renewal features CD56^dimCD16^bright NK cells in the blood of patients with ABMR would help for timely therapeutic intervention.

« Back to 2020 American Transplant Congress