[Use of flow cytometry for HLA B27 phenotyping: study of a HLA B7/HLA B27 double marker technique].

Among HLA-associated diseases, the strong association between HLA B27 and ankylosing spondylitis (AS) allows to perform HLA B27 typing for the diagnosis of this disease. The technique described: double immunostaining anti-HLA B7/HLA B27 on whole blood samples and analysis by flow cytometry is a rapid method for the detection of HLA B27 antigen. We have compared the results obtained with those of the TERASAKI microlymphocytotoxicity reference method on a population of 300 patients. The absence of false negative results indicates that this test is suitable for AS screening. The use of two monoclonal antibodies proves to be effective in eliminating cross reactions described with HLA B7 flow cytometric techniques using single monoclonal antibody. This technique allows to restrict the use of microlymphocy-totoxicity to patients presenting with both HLA B7 and B27 positive reactivities.