KIR2DL2/2DL3-E(35) alleles are functionally stronger than -Q(35) alleles

Area of Science:

• Immunology
• Genetics
• Molecular Biology

Background:

• Killer cell immunoglobulin-like receptor (KIR)2DL2 and KIR2DL3 are alleles of a single locus within the KIR gene family.
• Polymorphisms in KIR2DL2/L3 are linked to various human diseases and are crucial for donor selection in allogeneic hematopoietic stem cell transplantation.
• The molecular basis for functional differences among KIR2DL2/L3 alleles remains largely undetermined.

Purpose of the Study:

• To investigate the molecular determinants of functional diversity among KIR2DL2/L3 alleles.
• To elucidate the impact of specific amino acid variations on KIR2DL2/L3 receptor function and Natural Killer (NK) cell activity.

Main Methods:

• Functional assays including cytotoxicity assays to measure NK cell killing efficiency.
• Molecular modeling to analyze the structural and interaction dynamics of KIR2DL2/L3 alleles.
• Genotyping to identify KIR2DL2/L3 alleles with specific amino acid residues.

Main Results:

• KIR2DL2/L3 alleles with glutamic acid at position 35 (E35) exhibit stronger function compared to those with glutamine (Q35).
• NK cells from HLA-C1 positive donors expressing KIR2DL2/L3-E35 demonstrated enhanced cytotoxicity against target cells lacking ligands, suggesting improved NK cell licensing.
• Molecular modeling indicated that E35 stabilizes the KIR2DL2/L3 dimer through interaction with histidine at position 55, reducing entropic loss upon HLA-C ligand binding.

Conclusions:

• The amino acid at position 35 significantly influences KIR2DL2/L3 receptor function, with E35 conferring enhanced activity.
• These findings provide critical insights into KIR2DL2/L3-mediated immune responses and have implications for disease associations.
• Understanding these molecular differences is vital for optimizing donor selection in allogeneic stem cell transplantation and managing KIR2DL2/L3-associated conditions.