Immune Function and Aging among Tsimane Forager-Horticulturalists

Hillard S. Kaplan, University of New Mexico
Aaron Blackwell, University of California, Santa Barbara
Jon Stieglitz, University of New Mexico
Michael D. Gurven, University of California, Santa Barbara

While the biology of human immunity must have evolved in response to much higher pathogen stress than exists today, almost nothing is known about immunosenescence among premodern populations. Tsimane forager-farmers experience high rates of acute and chronic infections throughout life. Using flow cytometry and clinical exams on a sample of 500 Tsimane adults age 40+, we find that depletion of naïve T lymphocytes occurs more rapidly among the Tsimane than in populations with lower pathogen burden. Naïve T- and B-cell depletion are associated with increased natural killer cell (NKC) counts. We also find effects of sex, Body mass index, hematocrit and eosinophil counts on lymphocyte subsets. Our results provide initial evidence that high pathogen exposure results in more rapid immunosenescence, particularly for acquired immunity. Greater reliance on innate immunity with age might represent a compensatory response. Overall, however, Tsimane do maintain robust immune function through the eighth decade of life.