ROUTINE HLA-B27 TYPING BY FLOW-CYTOMETRY - DIFFERENTIATION OF THE PRODUCTS OF HLA-B-ASTERISK-2702, B-ASTERISK-2705 AND B-ASTERISK-2708

Patient HLA-B27 typing is widely performed as an aid to the diagnosis of several diseases, particularly ankylosing spondylitis. Typing by fl ow cytometry, using monoclonal antibodies, has been shown to be a pote ntially useful alternative to classical serology on account of its spe ed, simplicity and economy. However, we required a flow cytometry typi ng procedure that would accurately differentiate HLA-B27 (Bw4) from B2 708 (Bw6) and not be confounded by other HLA-B7/B27 cross-reactive gro up antigens. Accordingly, we evaluated the simultaneous use of two mon oclonal antibody preparations, ABC-m3-FITC (anti-B27 + weak B7)/BB7.1- PE (anti-B7) and FD705-FITC (anti-B27), by testing a highly selected p anel of 62 reference lymphocytes containing examples of all HLA-B7/B27 cross-reactive group antigens, including: HLA-B42, B47, B48, B73, B70 3, B2702, B2705 and B2708. In addition, 268 whole blood samples from r outine patient requests for B27-associated disease typing were tested in parallel with HLA-B typing using the standard complement-dependent microlymphocytoxicity test. The detailed specificity of the three mono clonal antibodies was established and the products of HLA-B2702, B*27 05 and B2708 were found to be readily differentiated from each other and all other HLA-B7/B27 cross-reactive HLA-B antigens.