AbstractThe phenotypic association between the non‐assigned high‐incidence antigen Joaand the Gyacollection antigens Gyaand Hy was investigated by haemagglutination studies, flow cytometric analysis, immune precipitation and immunoblotting experiments. In haemagglutination tests anti‐Joagave the same pattern of reactivity with erythrocytes pre‐treated with pronase, trypsin, α‐chymotrypsin and thiol reducing agents as did anti‐Gyaand anti‐Hy. In addition, similar to that found for anti‐Gyaand anti‐Hy, anti Joaalso showed reduced binding, as determined by haemagglutination and flow cytometric analysis, to erythrocytes from patients with paroxysmal nocturnal haemoglobinuria. Immune precipitates prepared from radio‐iodinated antigen‐positive red cells with anti‐Joa, anti‐Gyaand anti‐Hy gave similar results – a major component of Mr49,000–60,000 (the Gya/Hy‐active glycoprotein) and a second component of Mr85,000–92,000 (this may be a dimer of the Gya/Hy‐active glycoprotein, or a coprecipitated protein). These immune precipitates, when probed with both anti‐Gyaand anti‐Hy under non‐reducing conditions, gave a positive immunoblotting reaction to both the Mr49,000–60,000 and the Mr85,000–92,000 components. These results strongly suggest that the Joaantigen is expressed on the same
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