Abstract
Objective
HLA–B27 is capable of forming in vitro a heavy‐chain homodimer structure lacking β~2~‐microglobulin. We undertook this study to ascertain if patients with spondylarthritis express β~2~‐microglobulin–free HLA–B27 heavy chains in the form of homodimers and receptors for HLA–B27 homodimers.
Methods
Expression of HLA–B27 heavy chains by mononuclear cells was analyzed by fluorescence‐activated cell sorter staining, Western blotting with the monoclonal antibody HC‐10, and 2‐dimensional isoelectric focusing. Fluorescence‐labeled tetrameric complexes of HLA–B27 heavy‐chain homodimers were constructed in which each dimer comprised one His‐tagged heavy chain and one biotinylated heavy chain, and were used to stain patient and control mononuclear cells and transfected cell lines.
Results
Patients with spondylarthritis expressed cell‐surface HLA–B27 homodimers. Populations of synovial and peripheral blood monocytes, and B and T lymphocytes from patients with spondylarthritis, and controls carried receptors for HLA–B27 homodimers. Experiments with transfected cell lines demonstrated that KIR3DL1 and KIR3DL2, and immunoglobulin‐like transcript 4 (ILT4), but not ILT2, are receptors for HLA–B27 homodimers.
Conclusion
Patients with spondylarthritis express both HLA–B27 heavy‐chain homodimers and receptors for HLA–B27 homodimers. This may be of significance with regard to disease pathogenesis.