The 89th Annual Meeting of the American Association of Physical Anthropologists (2020)

Investment in innate immune defense in northern Kenya


1Anthropology, Grinnell College, 2Biological Chemistry, Grinnell College, 3Biomarker Laboratory for Anthropological Research, Michigan State University, 4Anthropology, Michigan State University

April 16, 2020 , Platinum Ballroom Add to calendar

Life history theory has great potential to facilitate coherent explanation of variations in investment patterns between innate and acquired immunity. Due to the importance of resource allocation and conservation, tradeoffs between innate and acquired immunity may be influenced by internal and external conditions. Among infants who are too young to exhibit acquired immunity but protected by passive immunity from breast milk, febrile response may represent elevated investment in innate immunity. We tested the hypothesis that nutritional scarcity, low pathogen exposure, and high extrinsic mortality risk during development favors greater investments in innate immunity as indicated by higher odds of fever among breastfed infants. Archived data from Ariaal communities of northern Kenya (n=79) were utilized. Maternal energy, serum homocysteine (high levels indicate folate/vitamin B-12 deficiency), milk folate (FOLR1) and energy contents were indicators of nutritional abundance. Exclusive breastfeeding represented low pathogen exposure. Male sex and high parity represented high extrinsic mortality risk. Logistic regression models estimated the odds of fever associated with these variables. Folate/vitamin B-12 scarcity (homocysteine) and FOLR1 were associated with higher odds of infant fever (OR 1.307, p=0.020; OR 1.14 p=0.019, respectively). Conversely, energy scarcity (maternal energy deficiency) and high parity were associated with lower odds of infant fever (OR 0.135, p=0.016; OR 0.080, p=0.010 respectively). Overall, the associations between energy scarcity, milk FOLR1, and high parity, contradict our initial hypothesis, suggesting that more complex relationships exist between innate and acquired immunity. Therefore, different nutritional resources may variably influence the level of investment in innate immunity among infants.

Support: Summer Research Opportunity Program and the Department of Anthropology, Michigan State University; National Science Foundation (BCS-0622358, BCS-1638167); Wenner-Gren Foundation for Anthropological Research (Gr. 7460, Gr. 9278).