Flow cytometric screening for the HLA-B27 antigen on peripheral blood lymphocytes.

HLA-B27 is common to the entire group of seronegative spondyloarthropathies, and assessment of HLA-B27 is of diagnostic importance if any of these diseases are considered. Among the alternatives to traditional typing by the complement-dependent cytotoxicity assay, flow cytometric HLA-B27 screening is most widely used in general diagnostic laboratories, as it is simple, rapid, and cost effective. This unit describes screening for HLA-B27 on peripheral blood lymphocytes using more than one HLA-B27 monoclonal antibody to detect possible cross-reactivity with non-HLA-B27 antigens. Screening is hampered by the lack of true monospecific anti-HLA-B27 monoclonal antibodies. Cross-reactivities of anti-HLA-B27 with other HLA-B antigens have been reported. The authors recommend use of GS145.2 and FD705 antibodies, as this combination avoids most false-positive conclusions. Lyse-and-wash sample processing is employed. A multiparameter flow methodology is applied. Three to four parameters-forward scatter, side scatter, HLA-B27 expression, and, in some cases CD3 or B7 expression-are acquired.