Fig. 3. Polymorphisms and post-translational modifications in the Ig variable domain can affect antigen binding.

A Antibody specificity is determined by the amino-acid composition of the variable region. B Polymorphisms at residues which are critical for the antibody-antigen interaction can result in loss of binding capacity [23, 65, 71]. Not all antibody residues are essential for antigen recognition (C) and Ig polymorphisms at positions that are not critical for binding may have little to no effect on the antibody binding capacity. D In addition to amino-acid changes, post-translational modifications in the variable domain may also affect the binding capacity of an antibody by either enhancing or abolishing it [83].