Humans, like all organisms, face competing demands when allocating limited resources, such as energy and nutrients, towards competing demands like growth, immune function, and reproduction. As a consequence, growth during childhood is highly plastic. Undernourished or malnourished children grow at slower rates and reach shorter adult statures than those who are well nourished. Exposure to infectious diseases and pathogens also causes delayed growth and reduces adult stature. Resource availability and pathogen exposure also change the development of the immune system. The immune system is made up of multiple branches of immunity which fight different types of pathogens and entail different costs. Thus, the immune system develops in order to respond adaptively to local threats. In developing populations, two factors which affect resource availability and pathogen exposure are family size and market integration, or the degree to which individuals participate in market economies as opposed to engaging in traditional subsistence activities such as hunting, fishing, and horticulture.
This research will investigate the effects of family size and market integration on growth and immune function in children living in the Ecuadorian Amazon. These children come from an indigenous Amazonian population known as the Shuar who traditionally subsisted on hunting, fishing, and horticulture. Today Shuar live across a range of circumstances, from urban to traditional. It has been previously shown that many Shuar children have growth that falls below international standards and varies with distance from towns, subsistence, and family size. This research will test the hypothesis that in addition to growth, large family size will limit resources for children and therefore decrease total immune function, and alter the development of the immune system to use forms of immunity such as inflammation, as opposed to costlier forms of immunity such as cell-mediated immunity. This study will also examine the impact of market integration on growth and immune system function. The study will measure 300 children in three Shuar villages that differ in terms of market integration and distance to urban centers. Data will be collected on growth status, resource availability, market integration and subsistence activities, and family composition. Biomarkers in dried blood spots will be used to evaluate the status of the immune system for each child. By collecting all of these measures together, this study will show how immune function and growth vary across familial and economic circumstances.
This project will provide new information about how immunity is regulated across environments and how immunity and growth interact. On a basic level, this research will contribute to our knowledge of the development and functioning of the immune system. This information may help us to understand things such as the connection between inflammation, obesity, and heart disease, and the increase in asthma and allergy lately seen in many Western populations. This project will also inform development initiatives by providing information on the health consequences of cultural changes occurring in the developing world.
