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Abstract

Objective—To characterize age-associated changes in lymphocyte population subsets and immunoglobulin isotypes.

Animals—30 healthy young light-breed horses (5 to 12 years old) and 30 healthy aged light-breed horses (> 20 years old).

Procedure—Lymphocyte subset populations were identified, using monoclonal antibodies to cell surface markers CD5, CD4, CD8, and IgG. Subset populations were quantitated by use of flow cytometric analysis of antibody-stained cells. Serum immunoglobulin concentration was determined using single radial immunodiffusion.

Results—Absolute cell counts of total lymphocytes, T cells, CD4+ and CD8+ T cells, and B cells were decreased in aged horses, compared with young horses. There was a significant decrease in the percentage of CD8+ cells and an increase in the CD4+-to- CD8+ cell ratio in the aged population, compared with young horses. However, serum concentration of IgG, IgG(T), IgM, or IgA did not differ with age.

Conclusions and Clinical Relevance—In horses, total lymphocyte count and lymphocyte subset cell counts decrease with age. Age-matched control values are necessary for optimal evaluation of hematologic variables in aged horses. The decrease in lymphocyte subset cell counts in healthy aged horses mimics that seen in other species and may contribute to an age-associated decrease in immunocompetency. ( Am J Vet Res 2001;62:1413–1417)

Full access
in American Journal of Veterinary Research

Abstract

Objectives

To compare hematologic and serum biochemical variables and plasma ACTH concentration between healthy horses 5 to 12 years old and those more than 20 years old.

Animals

30 healthy horses 5 to 12 years old and 30 healthy horses more than 20 years old.

Procedures

Venous blood was collected from all horses, and CBC and serum biochemical analysis were performed for each horse. Plasma ACTH concentration was determined by radioimmunoassay. Student's paired t-test or the Mann-Whitney rank sum test was used to compare values between control and aged horse groups.

Results

Compared with values for control horses, aged horses had significantly higher erythrocyte mean cell volume and mean cell hemoglobin. Aged horses also had significantly decreased total lymphocyte count. Five aged horses had lymphocyte count that was lower than the low reference limit as established for horses in our laboratory. Differences between control and aged horses for serum biochemical or plasma ACTH values were not significant.

Conclusion

Compared with younger adult horses, those more than 20 years old have some hematologic differences, but there is no apparent effect of aging on baseline plasma ACTH concentration.

Clinical Relevance

It is important to establish age-matched control values for optimal interpretation of clinicopathologic variables. (Am J Vet Res 1998;59: 1247–1251)

Free access
in American Journal of Veterinary Research