Background/Purpose:

KIR3DL2 is a Killer cell Immunoglobulin-like Receptor which binds to HLA class I including HLA-B27 (B27) β2m-free heavy chains (FHC) and HLA-A3/A11. KIR3DL2 is comprised of 3 immunoglobulin-like domains (D0, D1 and D2) which together determine binding to HLA-class I. 

We have shown that KIR3DL2 expression is enriched on a subset of CD4 T cells known as Th17 cells which produce proinflammatory mediators including IL-17 in spondyloarthritis (SpA). Indeed, we have also shown that inhibiting KIR3DL2 binding to HLA-B27 inhibits T cell production of IL-17 in vitro. We hypothesise that HLA-class I binding to KIR3DL2 promotes Th17 differentiation and that targeting this interaction could be therapeutically beneficial in disease. A detailed characterization of the KIR3DL2-B27 binding face could assist the development more specific molecular inhibitors of this interaction.

Methods:

We developed KIR3DL2-expressing cell lines, HLA-class I tetramers and KIR3DL2Fc fusion proteins to study KIR3DL2 ligand interactions. We also developed KIR3DL2CD3ε expressing Jurkat T reporter cells which produce IL-2 when stimulated with HLA- class I ligands.

Results:

KIR3DL2 binds more strongly to HLA-B27 free heavy chains than other HLA-class I ligands. This interaction is inhibited by B27 FHC-reactive antibodies and KIR3DL2 antibodies. The recent crystal structure of KIR3DL1 suggests that the D0 domain contacts a region that is conserved between many different HLA class I. Our results show that antibodies against the D0 domain of KIR3DL2 inhibit binding to B27.

We also studied the effect of targeted mutagenesis of potential contact amino acids in the D0 domain of KIR3DL2 shared with the D0 domain of KIR3DL1 on binding of B27 and other HLA class I. Since KIR3DL1 binds more weakly to B27 FHC than KIR3DL2, we studied the effect of mutating amino acids in KIR3DL2 close to these contact residues to the corresponding residues in KIR3DL1 on binding of B27 and other ligands.

Mutagenesis of key contact residues in the D0 domain of KIR3DL2 abolished or enhanced binding to B27 while not affecting binding to other ligands. 

Conclusion:

We have shown that B27 FHC binding to the immune receptor KIR3DL2 promotes the survival of IL-23 receptor expressing CD4 T cells and innate lymphocyte cell subsets.  Stronger binding of B27 FHC to KIR3DL2 could promote the survival of CD4 T cells and innate lymphocytes in SpA, accounting for our observations of increased proportions of these cells in patients.  A detailed characterization of the KIR3DL2-B27 binding face will assist the development of more specific molecular inhibitors of this interaction with the potential for development as novel therapeutics.

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« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/molecular-characterisation-of-the-killer-cell-immunoglobulin-like-receptor-3dl2-binding-to-aberrant-hla-b27-heavy-chains-in-spondyloarthritis/