¹Integrative Anthroplogical Sciences, University of California, Santa Barbara, ²Proyecto Tsimane' de Salud y Antropología, San Borja, Bolivia, ³Department of Anthropology, University of New Mexico, Albuquerque, NM

Saturday 9:45-10:00, Parlors

The relative proportion of different lymphocyte subsets varies between populations, yet data relating this variation to broader life-history patterns is limited. We address this lack by testing for trade-offs between growth and lymphocyte subset counts in the Tsimane, a population of forager-horticulturalists with high infectious exposure. Using flow cytometry, we identified T-cells (CD4+, CD8+), B-cells (CD19+), NK-cells (CD56+), and naïve T-cells (CD45RA+) in 540 blood samples. We tested for trade-offs using change in age standardized height (ΔHR) from the previous year. Total lymphocyte count (β = 1.46 cm/1000 cells/yr (CKY), p < 0.01), CD4 count (β = 6.86 CKY, p < 0.01), and percent naïve CD4 cells (β = 12.90 cm/100%/yr, p = 0.07) were all associated with positive ΔHR, while NK-cell count (β = -5.93 CKY, p = 0.07) and CD8 cell count (β = -6.01 CKY, p = 0.01) were associated with negative changes in ΔHR. Overall Tsimane had lower CD4/CD8 ratios, CD4 counts, and naïve CD4 proportions, and higher NK-cell counts than most age-matched populations in North America, Europe, and Africa. These results suggest the Tsimane pathogenic environment may deplete CD4 cells and reduce available naïve cells, and increase production of NK-cells, and that these effects are related to poorer relative growth scores.

Supported by NIH/NIA grants R01AG024119-06 and 2P01AG022500-06A1