A foal's immune system is known to be weak and immature, but new cell-based research suggests that "immunodeficiency" might be too broad a term to define the disease-fighting capacity of the youngest horses.

The research is overturning old theories about foal immunity, which could lead to improved disease prevention methods and more effective treatments for sick foals, according to Bettina Wagner, DVM, PhD, researcher at the College of Veterinary Medicine at Cornell University in Ithaca.

By studying the activity of certain immune-specific cells, scientists at Cornell have determined that some adaptive immune responses in foals are actually similar to those in adult horses. Furthermore, their responses tend to follow a different cell-based pattern than previously thought, Wagner said.

Immune responses come in large part from several different kinds of "T helper" cells, which scientists call "Th." Each kind of Th cell plays a different role in fighting diseases. For example, in the horse, Th1 cells help fight against infections inside the cells themselves. Th2 cells work to defend the body against bacteria and viruses outside the cells