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Clinical and Diagnostic Laboratory Immunology, September 2003, p. 870-875, Vol. 10, No. 5
1071-412X/03/$08.00+0     DOI: 10.1128/CDLI.10.5.870-875.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Lymphocyte Modulation in a Baboon Model of Immunosenescence

Lakshmi Jayashankar,¹ Kathleen M. Brasky,² John A. Ward,³ and Roberta Attanasio^1,4*

Department of Biology,¹ Gerontology Institute, Georgia State University, Atlanta, Georgia 30303-3088,⁴ Department of Laboratory Animal Medicine, Southwest Foundation for Biomedical Research, San Antonio, Texas 78245-0549,² Department of Clinical Investigation, Brooke Army Medical Center, Fort Sam Houston, Texas 78234-6315³

Received 4 March 2003/ Returned for modification 5 June 2003/ Accepted 14 July 2003

The age-related modulation of lymphocyte number and function was assessed in a nonhuman primate model consisting of healthy olive baboons (Papio cynocephalus anubis) of ages encompassing the entire life span of this species. The objectives of this study were to characterize an animal model of immunosenescence and to assess whether or not age should be considered when designing studies for the evaluation of vaccine candidates in baboons. Specifically the following parameters were assessed in baboons from 6 months to 26 years of age: relative numbers of B lymphocytes, CD4⁺ and CD8⁺ T lymphocytes, and T lymphocytes expressing CD28, CD25, and phytohemagglutinin-stimulated lymphoproliferative activity; and concentrations of total immunoglobulin, soluble interleukin-2 receptor , and soluble CD30 in serum. There was a statistically significant effect of age on lymphocyte numbers. As age increased, relative B-cell numbers (ranging from 6 to 50%) decreased (P < 0.001) and relative T-cell numbers (ranging from 28 to 80%) increased (P < 0.001). The increase in T-cell numbers involved both the CD4⁺ and CD8⁺ subsets. In addition, there was a significant negative correlation of age with levels of soluble interleukin-2 receptor in serum. Modulation of lymphocyte numbers appears to occur gradually during the entire baboon life span, thus suggesting the presence of an age-related developmentally regulated process. These findings indicate that baboons represent a potentially useful model to study selected phenomena related to immunosenescence. These findings also indicate that, when using the baboon model for vaccine or other experimental protocols requiring the assessment of immune responses, it would be appropriate to take into account the age of the animals in the study design.

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* Corresponding author. Mailing address: Department of Biology, Georgia State University, MSC8L0389, 33 Gilmer St. SE, Unit 8, Atlanta, GA 30303-3088. Phone: (404) 651-0589. Fax: (404) 651-2509. E-mail: rattanasio{at}gsu.edu.

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Clinical and Diagnostic Laboratory Immunology, September 2003, p. 870-875, Vol. 10, No. 5
1071-412X/03/$08.00+0     DOI: 10.1128/CDLI.10.5.870-875.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

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