Research Studies Quarterback of the Horse’s Immune System

What happens if the quarterback of the immune system goes rogue?

In a study set to begin in June 2023, Ontario Veterinary College researcher, Dr. Janet Beeler-Marfisi, will be looking at cellular responses to the agents that cause asthma in horses.

While studies on equine asthma have been ongoing for more than 40 years, researchers don’t know why some horses are more prone to develop heaves when exposed to the same environmental factors as horses that do not get heaves.

Much focus has been placed on researching lymphocytes (white blood cells that help the body fight viruses) but Beeler-Marfisi’s study will be looking at macrophage responses (white blood cells that stimulate the action of other immune cells) because they are the cells that “call the shots”.

“When the horse breathes in dust, it’s a macrophage that tells the horse’s immune system whether it’s something they can safely ignore or something that they should respond to,” says Beeler-Marfisi, a professor in OVC’s Department of Pathobiology. “To me, it makes sense to study the cells that call the shots, rather than those being told what to do (lymphocytes).”

The culprits of asthma are plentiful around the barn - from the endotoxins found in manure, particles that are released when bacteria rupture or disintegrate, to the dust found in the hay horses eat. “Even good quality hay will have a large number of mold spores in it and those play a role in the development or heaves in horses that are susceptible to it,” says Beeler-Marfisi.

Her study aims to find out if macrophages, the quarterbacks of the horse’s immune system, are behaving like they should when these challenges to the horse’s respiratory system are encountered.

Communications from the macrophage’s nucleus (the computer or brain of the cell) are sent through messenger RNA which tells the rest of the cell (or factory) to make proteins (the product) such as proinflammatory or anti-inflammatory proteins.

This research seeks to reveal whether macrophages of heaves-prone horses are the true culprit in the development of heaves.

Beeler-Marfisi said 1 in 7 horses in Canada are predicted to suffer from asthma. She suggests that purchasing high-quality hay, steaming or soaking it to reduce dusts that cause asthma, wetting aisles before sweeping and keeping barns well ventilated are good preventative measures.

Funding for this project is being provided by Equine Guelph.

This is adapted from an article originally published on the Equine Guelph Horse Portal website.