Can body size impact how an immune system fights disease? Does an elephant have a different immune system than a mouse?
According to University of South Florida College of Public Health (COPH) professor Dr. Lynn (Marty) Martin and colleagues, it’s a subject that’s been virtually unstudied.
Dr. Martin and others recently published the article “The effects of body mass on immune cell concentrations of terrestrial mammals” in the journal The American Naturalist. The journal posted the article online in September.
The group studied whether body size was related to concentrations of two important immune cell types (lymphocytes and neutrophils) in the blood of hundreds of mammalian species ― from tiny Jamaican fruit bats to elephants and giant killer whales.
And what they found was that size does, indeed, matter.
While the amount of lymphocytes ― immune cells that kill viruses and help the body make antibodies ― remained the same per liter of blood in big and small mammals, neutrophils, which kill or engulf bacteria and other infectious agents, were disproportionately more numerous in bigger species.
“One possibility for why lymphocytes remained the same,” said Dr. Martin, who specializes in global health and disease ecology, “is because they are a very diverse class of cells, meaning they perform many functions. We need better tools to count different types of lymphocytes before we’re likely to see any patterns.”
On the other hand, Dr. Martin added, bigger mammals have disproportionately more neutrophils than their smaller counterparts, perhaps due to cell replication.Friday Letter Submission, Publish on November 01