Immunoradiometric assay for the rapid detection of HLA-B27

A new method for the rapid detection of the HLA-B27 antigen is discussed which consists of a direct immunoradiometric assay (IRA) utilizing a 125I-labelled, HLA-B27 specific monoclonal antibody to detect HLA-B27 in whole citrated blood. Thus far, the assay has been used to assign HLA-B27 status in a population study involving 142 individuals; 36 subjects were HLA-B27+ by conventional microcytotoxicity and all 36 were detected by the new IRA and all 106 B27- individuals were also accurately assigned by IRA. The problem of detection of the cross-reactive HLA antigen HLA-B7 was overcome by blocking the reactive sites on HLA-B7 molecules with the HLA-B7 specific antibody, BB7.1. This new assay enables accurate detection of HLA-B27 within 30 min of venepuncture and should facilitate the assessment of HLA-B27 status in tissue typing laboratories.