Production of human monoclonal anti-Jk3, recognising an epitope including the Jka/Jkb polymorphic site of the Kidd glycoprotein

SUMMARY Background and objectives The Kidd blood group system consists of polymorphic antigens, Jka (JK1) and Jkb (JK2), and a high‐incidence antigen, Jk3. Anti‐Jk3 is often observed in immunised Jk(a−b−) individuals. In this study, we aimed to establish a human hybridoma cell line secreting monoclonal anti‐Jk3 (HIRO‐294). Materials and methods Peripheral blood lymphocytes of a Filipino woman with the Jk(a−b−) phenotype having anti‐Jk3 were transformed with Epstein‐Barr virus and then hybridised with the myeloma cell line JMS‐3 using the polyethylene glycol (PEG) method. The reactivity and specificity of the anti‐Jk3 were examined by serology and flow cytometry. Results Four hybridoma clones secreting anti‐Jk3 were established and the antibody from one of these clones, HIRO‐294, was examined. The reactivity of HIRO‐294 was positive with 227 Jk(a+b−) red blood cells (RBCs), 298 Jk(a−b+) RBCs, and 1043 Jk(a+b+) RBCs, but was negative with 21 Jk(a−b−) RBCs. Eluates from Jk(a+b−) RBCs and Jk(a−b+) RBCs sensitised with the anti‐Jk3 were cross‐reacted with Jk(a−b+) RBCs and Jk(a+b−) RBCs, respectively. The reactivity of HIRO‐294 was enhanced by the treatment of RBCs with ficin, trypsin, pronase and α‐chymotrypsin, but was not changed by their treatment with neuraminidase, dithiothreitol and ethylenediaminetetraacetic acid (EDTA) glycine acid (GA). The RBCs sensitised by the anti‐Jk3 were not agglutinated with the commercial reagents of anti‐Jka and anti‐Jkb by saline test, whereas the nonsensitised RBCs or those sensitised by monoclonal anti‐D [HIRO‐3, immunoglobulin G (IgG) class] were agglutinated with those reagents. Conclusions We established a human hybridoma cell line secreting monoclonal anti‐Jk3 (HIRO‐294). This antibody had unique specificity, recognising the Kidd glycoprotein including the Jka/Jkb polymorphic site.