Phylogenetic analysis of hominid and Old World monkey IgGs and FcγRs. Phylogenetic trees were generated from the amino acid sequences of each of the IgG subclasses (IgG1–4) (A) and three FcγRs (FcγR1, FcγR2A and FcγR3A) (B) of humans, chimpanzees, baboons, pig-tailed macaques and rhesus macaques. Trees were constructed with using the maximum likelihood method and Jones-Taylor-Thornton substitution model with 1,000 bootstrap replicates. Trees were rooted on murine IgHG1, IgGh2a and FcγR2B sequences and nodes with bootstrap values less than 0.5 were collapsed using TreeGraph software. The scale bars indicate amino acid substitutions per site.