Monkey immune systems linked to sexual activity

Associated Press

CHARLOTTESVILLE, Va. — Promiscuous species of monkeys appear to have stronger immune systems than less-active ones, researchers say.

"The most sexually active species of primates may have evolved elevated immune systems as a defense mechanism against disease," said Charles Nunn, a University of Virginia biology researcher who led the study, published in the latest issue of the journal Science.

Nunn and colleagues studied 20 years of data on 41 primate species from zoos around the world. They found that the most promiscuous have high levels of basal white blood cells, the body’s first defense against infection. Monogamous species, like the white-handed gibbon or Titi monkey, have lower levels.

Other risk factors for disease, such as crowded living conditions or contact with other germs, had little effect on immune response, said co-author John Gittleman, a biology professor.

Humans have white blood cell counts similar to those in primarily monogamous species, the researchers said.

Jeffrey Frelinger, a professor of microbiology and immunology at the University of North Carolina, said the correlation between promiscuity and higher white blood cell counts is interesting, but he cautioned that the study "doesn’t disentangle causes and effects."

He also noted that the study looks at total white cells but doesn’t examine their ability to fight infection.