KIR3DS1-Specific D0 Domain Polymorphisms Disrupt KIR3DL1 Surface Expression and HLA Binding

Area of Science:

• Immunology
• Genetics

Background:

• KIR3DL1 is an inhibitory receptor on NK cells that interacts with HLA-A and HLA-B alleles carrying the Bw4 epitope.
• Amino acid variations in KIR3DL1 affect its surface expression and HLA binding affinity.
• KIR3DL1 and KIR3DS1 are homologous receptors, but KIR3DS1 does not bind the same ligand.

Purpose of the Study:

• To investigate the functional consequences of KIR3DS1-specific polymorphisms on the KIR3DL1*009 allele.
• To analyze the impact of these polymorphisms on KIR3DL1*009 surface expression, HLA binding, and NK cell function.

Main Methods:

• Flow cytometry was used to assess surface expression on primary human NK cells and transfected HEK293T cells.
• Recombinant proteins were utilized to analyze the binding affinity of KIR3DL1 variants to HLA.
• Site-directed mutagenesis identified specific amino acid positions responsible for observed functional changes.

Main Results:

• KIR3DL1*009 exhibited significantly lower surface expression compared to KIR3DL1*001.
• KIR3DL1*009 showed minimal binding to HLA, unlike KIR3DL1*001 and KIR3DL1*005.
• Polymorphisms at positions 58 and 92 in the D0 domain were identified as critical for reduced surface expression and binding.
• KIR3DL1*009(+) NK cells were less inhibited by HLA-Bw4(+) target cells than KIR3DL1*001(+) NK cells.

Conclusions:

• KIR3DS1-derived polymorphisms in KIR3DL1*009 impair its surface expression and HLA binding capabilities.
• These alterations lead to reduced inhibitory function of KIR3DL1*009(+) NK cells against HLA-Bw4(+) targets.
• The study provides insights into how specific extracellular polymorphisms modulate KIR3DL1 function.