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Allotypes have been identified for five of the human IGHC genes, the IGHG1, IGHG2, IGHG3, IGHA2 and IGHE genes, and are designated as G1m, G2m, G3m, A2m, and Em allotypes, respectively. These allotypes are inherited in fixed combinations, or Gm-Am-Em haplotypes.

Gm allotypes and Gm haplotypes

G1m allotypes

A2m allotypes