The discovery highlights diversity in immune system genes.

The University of Edinburgh’s Royal (Dick) School of Veterinary Studies have identified a range of newly uncovered gene sequences in horses’ immune systems.

The discovery of these new gene sequences reveals a larger variety of equine immune genes than were previously known, providing a stronger insight into the genetic makeup of horses and how they fight disease.

The researchers collaborated with scientists in England, Iceland and Norway to conduct analysis of genetic data from 168 horses, across three European breeds. The group used genetic sequencing technology to examine immune genes, known as Major Histocompatibility Complex (MHC), in Thoroughbred, Icelandic and Norwegian Fjords.

The analysis revealed a diversity in the immune systems’ genes when compared with horse populations which have evolved separately.

These gene sets come in two main types: MHCI and MHCII. Each type contains a complex arrangement of combinations which varies significantly per individual, supporting the immune system with recognising threats.

The analysis discovered 152 sequences of MHCI genes, which are responsible for monitoring infections within cells. It also found 117 new sequences of MHCII, which monitor for infections in surrounding cells.

There was a limited overlap in these gene types across the three horse breeds, which may mean that there is even greater MHC diversity in the global horse population.

Discovering these new genes may contribute to our knowledge of how MHC genes affect horses’ immune systems, as well as wider implications for clinical treatments.

It will also help with our understanding of equine health and disease, and inform breeding practices.

Dr Tim Connelley, research fellow at University of Edinburgh’s Roslin Institute, said: “We found a wide range of MHC genes and patterns of gene expression, allowing us to get a glimpse of how this set of genes may function in horses.

“These results could prove useful for vaccine development and novel cell-based therapies that are becoming more adopted in equine medicine."

The full study is published in the journal Cell.

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