Investigation of innate immune function in adult and geriatric horses

Vet Immunol Immunopathol. 2021 May;235:110207. doi: 10.1016/j.vetimm.2021.110207. Epub 2021 Feb 12.


In order to better understand the influence of age on innate immune function in horses, blood was collected from twelve adult horses (aged 10-16 years; mean: 13 years) and ten geriatric horses (aged 18-26 years; mean: 21.7 years) for analysis of plasma myeloperoxidase, complete blood counts, and cytokine and receptor expression in response to in vitro stimulation with heat-inactivated Rhodococcus equi, heat-inactivated Escherichia coli, and PMA/ionomycin. Gene expression was measured using RT-PCR for IFNγ, IL-1β, IL-6, IL-8, IL-10, IL-12α, IL-13, IL-17α, TLR2, TLR4, and TNFα. Endocrine function and body weight were measured to assess any potential impacts of ACTH, insulin, or body weight on immune function; none of the horses had pituitary pars intermedia dysfunction. The geriatric horse group had lower concentrations of plasma myeloperoxidase (P = 0.0459) and lower absolute monocyte counts (P = 0.0477); however, the difference in monocyte counts was no longer significant after outliers were removed. Additionally, only two significant differences in cytokine/receptor expression in whole blood were observed. Compared with adult horses, the geriatric horses had increased TNFα expression after in vitro stimulation with heat-inactivated R. equi (P = 0.0224) and had decreased IL-17α expression after PMA/ionomycin stimulation when one outlier was excluded (P = 0.0334). These changes may represent a compensatory mechanism by which geriatric horses could ensure adequate immune responses despite potentially dysfunctional neutrophil activity and/or decreased monocyte counts. Aging may influence equine innate immune function, and additional research is warranted to confirm and further explore these findings.

Keywords: Aged; Geriatric; Horse; Immune; Innate.

MeSH terms

  • Age Factors
  • Aging* / immunology
  • Animals
  • Blood Cells / immunology*
  • Blood Cells / physiology
  • Cytokines / genetics
  • Cytokines / immunology*
  • Escherichia coli / immunology
  • Gene Expression
  • Horses / immunology*
  • Immunity, Innate*
  • RNA, Messenger / genetics
  • Rhodococcus equi / immunology


  • Cytokines
  • RNA, Messenger

Supplementary concepts

  • Rhodococcus hoagii