Low Ranking Baboons Have Bad Immune Systems

A baboon. — Baboons can master one of the basic elements of reading, although they have no linguistic skills, a French team reports. The monkeys in this study learned how to tell the difference between printed sequences of letters that made up actual English words and other, nonsense sequences. (Image credit: J. Fagot)

Having a low social rank can have a bad impact on the immune system, new research suggests. Low ranking baboons had more trouble healing their wounds and fighting off infections.

On the other hand, high-ranking male baboons recover more quickly from injuries and are less likely to become ill than other males.

"In humans and animals, it has always been a big debate whether the stress of being on top is better or worse than the stress of being on the bottom," study researcher Beth Archie, of the University of Notre Dame, said in a statement. "Our results suggest that, while animals in both positions experience stress, several factors that go along with high rank might serve to protect males from the negative effects of stress."

The study was published today, May 21, in the journal Proceedings of the National Academy of Sciences.

The researchers examined 27 years of health records from the Amboseli Baboon Research Project in Kenya. They found that high rank is associated with faster wound healing. The finding is somewhat surprising, given that top-ranked males also experience high stress, which should suppress immune responses. They also found that social status is a better predictor of wound healing than age.

"The power of this study is in identifying the biological mechanisms that may confer health benefits to high-ranking members of society," George Gilchrist, program director in the National Science Foundation, said in a statement. "We know that humans have such benefits, but it took meticulous long-term research on baboon society to tease out the specific mechanisms."

The research team investigated how differences in age, physical condition, stress, reproductive effort and testosterone levels contribute to status-related differences in immune functions.

The researchers found that high-ranking males were less likely to become ill and recovered faster from injuries and illnesses than low-ranking males. The authors suggest that chronic stress, old age and poor physical condition associated with low rank may suppress immune function in low-ranking males.

"The complex interplay among social context, physiology and immune system-mediated health costs and benefits illustrates the power of interdisciplinary research," Carolyn Ehardt, also of the National Science Foundation, said in a statement. "This research begins to tease apart the trade-offs in both high and low status in primates, including ourselves, which may lead to understanding the effects of social status on death and disease — not inconsequential for society as a whole."

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