TOPOLOGY OF KELL BLOOD-GROUP PROTEIN AND THE EXPRESSION OF MULTIPLE ANTIGENS BY TRANSFECTED CELLS

Kell is one of the major blood group systems in human red blood cells (RBCs). The Kell antigens are carried on a 731 amino acid glycoprotein that is thought to span the erythrocyte membrane once. Rabbit antibod ies to three synthetic peptides, derived from different parts of the K ell protein, were used to determine the topology of Kell protein on th e RBC. Antibodies to a C-terminal peptide and to a peptide derived fro m amino acid residues 410 to 439 reacted with RBCs treated with 0.2 mo l/L dithiothreitol. An antibody to the N-terminal peptide reacted with inside-out RBC vesicles but not with right-side-out vesicles nor with intact RBCs, showing that Kell is a type II membrane protein and that the extracellular portion of the protein is folded by disulfide bonds . By transfection, Kell protein was expressed on the cell surface of s urrogate cells, and the transfected cells expressed similar antigenic properties as native RBCs. Kelt protein was expressed in COS-1 and K56 2 cells and in Sf9 cells infected by the Baculovirus system. Transfect ed K562 cells expressed several high-incidence antigens but not the lo w-incidence antigen K1. (C) 1994 by The American Society of Hematology .