Racing pushes Arabian racehorse immune systems harder than training gallops

Arabian racehorses respond to a race with a distinctly different immune and metabolic signature than they show after high-intensity training gallops, according to a longitudinal study published in BMC Veterinary Research. Researchers tracked eighteen horses across three matched exercise contexts—the first monitored high-intensity gallop of the training season, a comparable gallop after six to ten weeks of regular training, and an official race—and profiled leukocytes, T-cell subsets, monocyte populations, reactive oxygen species production and serum cytokines at rest, immediately after exercise and thirty to forty minutes later.

The within-horse repeated-measures design allowed each animal to serve as its own control, isolating the effect of exercise context from individual variation. Hematological assessment covered leukocyte indices and the granulocyte-to-lymphocyte ratio, while biochemical analyses measured lactate, glucose, total protein, albumin and globulin concentrations. Peripheral blood mononuclear cells were examined by flow cytometry, and a multiplex equine panel quantified serum cytokines and chemokines.

Racing produced the clearest physiological challenge. It was associated with leukocytosis and granulocytosis, both statistically robust, and with a delayed elevation of the granulocyte-to-lymphocyte ratio in the post-race sampling window. Lactate clearance was lower after racing than after either training gallop, indicating a prolonged metabolic recovery from the official effort.

Flow cytometry revealed that immune cell redistribution depended on the exercise context. CD8-positive T cells increased after both the first training gallop and racing. CD4-positive T cells fell after the first gallop but rose after the later training session and after racing, showing that the direction of the same cell-type response can flip depending on where the horse is in its training and competition schedule.

Regulatory T-cell populations also shifted in a phase-specific manner. CD4-positive and CD8-positive lymphocytes expressing FoxP3, a transcription factor marker of regulatory T cells, increased after the second training gallop but not after the other exercise contexts. This suggests that regular training, rather than the acute shock of racing or the season’s first hard effort, is associated with expansion of this immunoregulatory compartment in the circulation.

Monocyte subpopulations told a similar context-dependent story. CD14-positive MHCII-negative monocytes increased after the first training gallop and after racing, while CD14-negative MHCII-positive cells rose after the second training gallop and declined after the first gallop and the race.

Cytokine and chemokine responses were selective rather than uniform. After the race, the anti-inflammatory cytokine IL-10 increased, while the chemokines IL-8 and GRO decreased. The authors note that quantifiable responses varied among analytes, meaning the soluble mediator profile did not move as a single block but reflected distinct signaling changes tied to the racing context.

The study’s conclusions are deliberately measured: training phase and racing were associated with distinct short-term patterns of leukocyte redistribution, stimulated ROS-generating capacity and metabolic load. Because the work reports associations within a single season and a limited sample of eighteen horses, the findings characterize response patterns rather than establish causal mechanisms or long-term health outcomes.

Subject of Research: Immune and metabolic response profiles of Arabian racehorses across training and racing phases

Article Title: Biomarkers in motion: cytokine and flow-cytometric profiling of exercise-associated immune phenotypes in Arabian racehorses across training and racing phases

Article References: Dąbrowska, I., Grzędzicka-Agko, J., Żmigrodzka, M., & Witkowska-Piłaszewicz, O. (2026). Biomarkers in motion: cytokine and flow-cytometric profiling of exercise-associated immune phenotypes in Arabian racehorses across training and racing phases. BMC Veterinary Research. https://doi.org/10.1186/s12917-026-06055-w

Image Credits: AI Generated

DOI: 10.1186/s12917-026-06055-w

Keywords: Arabian racehorses, exercise immunology, flow cytometry, cytokines, leukocyte redistribution, reactive oxygen species, granulocyte-to-lymphocyte ratio, regulatory T cells, monocyte subsets, lactate clearance, veterinary research, Biomarkers