Species that fight infection effectively- A Mouse or An Elephant? Study
Among the Elephant & Mouse, what species is better at fighting an infection? is it a mouse or an elephant?! The body size is one of the most noticeable differences among these species, but the relationships between immune defenses and their body size have largely been unstudied.
Cynthia J. Downs, Hamilton College Assistant Professor of Biology, led a research study with co-authors Ned Dochtermann of North Dakota State University, Kirk Klasing at University of California, Davis, Ray Ball of Eckerd College, and Lynn (Marty) Martin at University of South Florida that investigated whether body masses were related to concentrations of 2 important immune cell types in the blood among hundreds of species of mammals ranging from the tiny Jamaican fruit bats (~40 g) to giant killer whales (~5,600 kg). Their study results appear in The Effects of Body Mass on Immune Cell Concentrations of Mammals, recently published online by The American Naturalist.
The scientists found that concentrations of lymphocytes, one type of white blood cell, did not change in any special way with the body sizes. A mouse and an elephant have the same number of lymphocytes per ml of their
blood.In contrast to this, big mammals had far, far more neutrophils in circulation than the small species. These neutrophils are involved in early immune responses to many different kinds of invaders including bacterias and even bigger parasites such as worms.
The scientists speculate that larger mammals might need much more circulating neutrophils to overcome the inherent advantages that infectious agents have over the animals they infect. This advantage arises because small organisms replicate their cells much faster than big organisms; to offset this benefit of being small, big organisms maintain a large pool of nasty cells to attack the invaders.
This study on finding species that fight infection effectively shows that for some types of immune defenses, large and small mammals are fundamentally different from each other. Downs and co-author Martin observed in their study that this insight may help in developing better ways to link the results from lab mice to improvements of human health. This study also helps in enabling researchers to make predictions about the immune systems of various species never before studied. The co-authors of the study speculate that these data could also even help wildlife managers predict how good a species could be as a host for a newly emerging disease.
