Antibody activity of heavy and light chains and recombined IgG of human IgG anti-D.

Four human sera with high titers of IgG anti-D were studied in recombination experiments with isolated heavy and light chain. The binding to the D antigen measured by hemagglutination with O,R1R2 erythrocytes was 30-60 times weaker with isolated anti-D heavy chains and with hybrids of anti-D heavy chains and pooled light chains than with the parent anti-D IgG. Light chains and hybrids of light chains from anti-D IgG and pooled heavy chains showed no binding. This indicates that the heavy chains are more important in antigen binding than the light chains in this system. It was also shown that the idiotypes need both heavy and light chains of the anti-D molecule to give a positive reaction with specific anti-idiotypic antiserum.