The flow cytometric labeling pattern in HLA-B27 detection may suggest cross reactivities

Background: The detection of HLA-B27 expression is one of the most powerful diagnostic tools in ankylosing spondylitis and other spondylarthropaties, hence the importance of a reliable and accurate detection method. Flow cytometry is often used as an alternative HLA-B27 typing technique, mainly because it is a rapid test. However, even though it is based on various monoclonal antibodies, their ability to bind to cross-reactive HLA-B molecules was demonstrated by various groups. Materials and methods: The HLA-B27 typing was performed by flow cytometry using the BD TM HLA-B27 System, and by the HLA-SSP and HLA-SSO typing techniques. Results: We were able to confirm some of the known cross-reactivities and evidence some new ones, as HLA-B18 and B35, in the context of a characteristic flow cytometric labeling pattern. Conclusions: flow cytometry can offer clues indicating the presence of HLA-B27 cross-reactive molecules, but such situations will require HLA typing by molecular biology techniques.