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Summary The reaction between a 7S incomplete anti‐D and ficin‐treated red cells was investigated using 131I‐labelled anti‐D. Ficin‐treatment brought about an increase in the value of the rate constant for association, and hence an increase in the value of the intrinsic binding constant. There was no evidence from the data that ficin treatment exposes additional antigen sites. Résumé La réaction entre un anti‐D incomplet 7S et les érythrocytes traités à la ficine a été recherchée en utilisant de l'anti‐D marqué au I131. Le traitement à la ficine assure une augmentation du degré de l'association, et, par conséquent, une augmentation de la constante de liaison intrinsèque. En outre, ces résultats démontrent que le traitement à la ficine n'augmente pas les sites antigèniques. Zusammenfassung Mit Hilfe von I131‐markiertem Anti‐D wurde die Reaktion zwischen inkompletten Anti‐D‐Antikürpern vom 7S‐Typ und ficinbehandelten Erythrozyten untersucht. Die Ficinbehandlung bewirkte eine Zunahme der Bindungsgeschwindigkeitskonstante mit entsprechender Zunahme der inneren Bindungskonstante. An Hand der Resultate konnte nicht bewiesen werden, daß durch Ficinbehandlung zusätzliche Antigendeterminanten freigelegt werden.

Monoclonal antibodies BRIC 18, BRIC 68, BRIC 107 and BRIC 203 recognize high-frequency epitopes absent from erythrocytes expressing the Ko phenotype. BRIC 107 has anti-k (K2)-like specificity. BRIC 203 has a unique specificity denoted anti-Kpbc. All four monoclonal antibodies identify an M(r) 95,600 erythrocyte membrane protein by immunoprecipitation from radio-iodinated erythrocytes. In quantitative binding studies using IgG it is estimated that there are from 2000 (BRIC 18) to 4000 (BRIC 68) copies of the Kell glycoprotein per erythrocyte. Using Fab fragments the estimates are in the range 4000 (BRIC 18) to 18,000 (BRIC 68) copies. In competitive binding assays the four epitopes defined by the BRIC monoclonal antibodies fall into two non-overlapping groups. The first group comprises BRIC 18, BRIC 68, BRIC 203 and an antibody (6-22) with anti-K14 specificity. The second group contains BRIC 107 and two further anti-k-like monoclonal antibodies (BS45 and OSK5). The results suggest that the polymorphisms encoded at the K/k and Kpa/Kpb/Kpc loci may be located in two spatially distinct regions of the Kell glycoprotein(s).