Islet cell antibodies in Sulawesi macaques

Older monkeys of the Sulawesian species Macaca nigra spontaneously develop a lesion in the pancreatic islets of Langerhans in which there is deposition of amyloid and gradual degeneration of all cells, which can lead eventually to development of diabetes mellitus. Islet cell antibodies (ICA), formed in response to the release of cellular antigens, can be used to detect the islet lesion and to monitor the progression of each monkey toward diabetes. Numerous M. nigra and one M. tonkeana in captivity have been tested, but it is unknown whether the islet lesion occurs in monkeys in their natural habitat of Sulawesi. Blood samples collected from M. maurus, M. tonkeana, and hybrid M. maurus/tonkeana were assayed for ICA. When all monkeys were considered together, 33% had ICA positive against beta cells and 14% had ICA positive against alpha and/or D cells. Appearance of ICA in blood of males was virtually the same as in females. These results are similar to those found in M. nigra examined in captivity. Since all Sulawesian species share a common genetic heritage, these results would support the appearance of this lesion in their natural habitat. Cause(s) for formation of the lesion and eventual development of diabetes are unknown. There may be genetic factors or genetic predisposition to environmental factors. If environmental factors are responsible, then they must be present not only in the wild, but either carried with the monkeys or universally available, since M. nigra born in captivity also develop the lesion and diabetes after physical maturity at ca. 7+ years.