In the present study, the peripheral blood leukocyte phenotypes, lymphocyte subset populations, and oxidative stress parameters were studied in cognitively characterized adult and aged dogs, in order to assess possible relationships between age, cognitive decline, and the immune status. Adult (N = 16, 2–7 years old) and aged (N = 29, older than 8 years) dogs underwent two testing procedures, for the assessment of spatial reversal learning and selective social attention abilities, which were shown to be sensitive to aging in pet dogs. Based on age and performance in cognitive testing, dogs were classified as adult not cognitively impaired (ADNI, N = 12), aged not cognitively impaired (AGNI, N = 19) and aged cognitively impaired (AGCI, N = 10). Immunological and oxidative stress parameters were compared across groups with the Kruskal-Wallis test. AGCI dogs displayed lower absolute CD4 cell count (p < 0.05) than ADNI and higher monocyte absolute count and percentage (p < 0.05) than AGNI whereas these parameters were not different between AGNI and ADNI. AGNI dogs had higher CD8 cell percentage than ADNI (p < 0.05). Both AGNI and AGCI dogs showed lower CD4/CD8 and CD21 count and percentage and higher neutrophil/lymphocyte and CD3/CD21 ratios (p < 0.05). None of the oxidative parameters showed any statistically significant difference among groups. These observations suggest that alterations in peripheral leukocyte populations may reflect age-related changes occurring within the central nervous system and disclose interesting perspectives for the dog as a model for studying the functional relationship between the nervous and immune systems during aging.
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Central nervous system
White blood cells
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This study was funded by a grant from the University of Padova (PRA 2010; Project coordinator: G. Gabai). Elisa Pitteri was supported by a PhD grant from the University of Padova. Authors are grateful to the student Silvia Saletti for helping with the cognitive tests and to Dr. Laura Da Dalt, Dr. Valentina Bertazzo, Dr. Carlo Poltronieri, and Mr. Tommaso Brogin for their skilled technical support.
Conflict of interest
None of the authors has a financial or personal relationship with other people or organizations that could inappropriately influence or bias the content of the paper.
PM participated in the design of the study, in the performance of the cognitive tests, performed the statistical analysis and contributed in drafting the manuscript. DB participated in the design of the study and in the manuscript drafting and coordinated the hematological and biochemical analyses. EP looked after and carried out the cognitive tests. AS set up and carried out the hematological and cytofluorimetric assays. LM participated in the design of the study, coordinated the cognitive tests, and looked after the final revision of the manuscript. GG conceived the study, participated in its design and coordination, and helped to draft the manuscript. All authors read and approved the final manuscript.
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Mongillo, P., Bertotto, D., Pitteri, E. et al. Peripheral leukocyte populations and oxidative stress biomarkers in aged dogs showing impaired cognitive abilities. AGE 37, 39 (2015). https://doi.org/10.1007/s11357-015-9778-9
- Cognitive abilities
- Lymphocyte subpopulations
- Oxidative stress