Production of antibodies to human immunoglobulins in a gibbon

Immunization of a chimpanzee, a gibbon, a baboon and a rhesus monkey with human globulins gave different results. While chimpanzees did not produce any anti-human antibodies, baboon and rhesus monkey responded by producing anti-human IgG antibodies that did not show subclass or allotype specificity. In the gibbon antiserum, on the other hand, six different antibodies were demonstrated with a specificity against one or more of the four human IgG subclasses, including one allotype. Comparative investigations of non-human primate species sera showed that one of the specificities detected by these antibodies, i.e., the allotype G1m(f), was restricted to man; the other five antibodies reacted with man and with two or more genera of apes. Lower primates did not share any of these antigenic determinants. The extent of immunological distance is parallel to the taxonomic classification. The gibbon shows that there are more similarities between man and chimpanzee or pygmy chimpanzee than between man and gorilla or orangutan.