Protein sequence of the V_H of Id proteins derived from the original and the relapsed tumor. Amino acids were deduced from DNA sequences of the respective clones and compared against the previously published consensus sequence.10 Dashes in the sequence indicate identity with the consensus sequence, and differences are indicated by single letters. X indicates undetermined amino acids. Positions of the CDR are marked. Changes in CDR2 thought to be critical for the loss of binding to treatment antibody 7D11 are underlined twice.