Figure 1. Human IgG isoallotype genetic variation and reactivities to anti-IgG subclass reagents.

Canonical sequences for each IgG subclass are shown in light blue, with all known intrasubclass variants within the hinge, CH2, and CH3 region shown below each canonical sequence. A summary of the reactivity with either monoclonal or polyclonal anti-IgG subclass–specific antibody is shown to the right, with blind spots (and their corrections) shown in red and cross-reactive antibodies (and their corrections) shown in blue. For clarity, variant amino acids that differ between IgG subclasses but that do not vary within a subclass (i.e., isoallotype) are not shown. For a more comprehensive view of all known amino acid differences between the 29 isoallotypes, please see ref. 21.