Human monoclonal antibodies with different fine-specificity for digoxin derivatives: Cloning of heavy and light chain variable region sequences

Human-mouse hybridoma cell lines producing human monoclonal antibodies against the cardiac glycoside digoxin were established after in vitro immunization or direct immortalization of human peripheral blood lymphocytes with digoxin. Three antibodies, designated M06, LH92 and LH 1 14, displayed different patterns of fine specificity against digoxin and several digoxin analogues, as elucidated by inhibition ELISA. All three monoclonal antibodies had p heavy chains, two of them (M06 and LH 114) had K light chains and one (LH92) A light chains. DNA encoding the variable regions of both heavy and light chains of the three antibodies were amplified from cDNA using the polymerase chain reaction (PCR). The nucleotide sequences of the amplified DNA were determined after subcloning of PCR fragments in M13 vectors. The deduced amino acid sequences revealed considerable sequence differences in the complementarity determining regions between the three antibodies