Natural killer-cell KIR repertoire reconstitution after haploidentical SCT

Area of Science:

• Immunology
• Hematology
• Transplantation

Background:

• Natural killer (NK) cells play a crucial role in immune surveillance and response.
• Killer-cell Ig-like receptors (KIRs) on NK cells regulate their activity through interactions with HLA ligands.
• Haploidentical stem cell transplantation (SCT) is a strategy to restore immune function, but donor-NK cell reconstitution is critical.

Purpose of the Study:

• To analyze the repertoire of donor-derived NK cells expressing KIRs after haploidentical SCT.
• To correlate the reconstitution hierarchy of specific NK cell subsets with clinical outcomes, specifically event-free survival (EFS).
• To determine the impact of KIR ligand matching/mismatching on EFS in AML patients undergoing haploidentical SCT.

Main Methods:

• Studied KIR/NK-cell group-2-Ag repertoires in 28 patients post-haploidentical SCT within 6 months.
• Assessed the reconstitution hierarchy of potentially alloreactive, single KIR+ NK cells based on HLA-C1, HLA-Bw4, and HLA-C2 binding.
• Correlated NK cell reconstitution patterns with EFS in AML patients.

Main Results:

• The reconstitution hierarchy of single KIR+ NK cells was HLA-C1 binding > HLA-Bw4 binding > HLA-C2 binding.
• In haploidentical SCT for AML, HLA-C1 mismatching in the graft-versus-host direction resulted in superior 5-year EFS (67±10%) compared to non-NK-alloreactive transplants (17±5%).
• HLA-C1 mismatching also yielded better EFS than HLA-C2 (35±10%) or HLA-Bw4 (44±17%) KIR ligand mismatches.

Conclusions:

• The kinetics of single KIR-expressing NK cell generation after haploidentical SCT vary among KIR receptors.
• These distinct reconstitution kinetics significantly influence patient survival post-transplant.
• HLA-C1 mismatching in the graft-versus-host direction is associated with the best EFS in AML patients undergoing haploidentical SCT.