Life history, immune function, and intestinal helminths: Trade-offs among immunoglobulin E, C-reactive protein, and growth in an Amazonian population.

OBJECTIVES Infection with helminths is associated with shifts in host immunity, including increased production of immunoglobulin E (IgE) and reduced inflammation. Given limited energy budgets, these shifts may involve changes in energy allocation toward competing demands. Here we test for potential trade-offs between growth, IgE, and the inflammatory marker C-reactive protein (CRP). METHODS Dried blood spots and anthropometrics were collected from 162 Shuar forager-horticulturalists from a village in southeastern Ecuador. Enzyme-linked immunosorbent assays (ELISAs) were used to measure IgE and CRP. Relationships among IgE, CRP, and anthropometrics were examined in three groups: children aged 2-7 years (n = 63), children aged 8-15 (n = 61), and adults over age 18 (n = 37). RESULTS Geometric mean IgE was 1,196 IU ml⁻¹ while geometric mean CRP was 1.33 mg l⁻¹. In children, IgE and CRP were negatively correlated (r = -0.21, P = 0.02, df = 122). Controlling for fat stores and age, IgE was associated with lower stature in children (t = -2.04, P = 0.04, df = 109), and adults (t = -3.29, P < 0.01, df = 33). In children there was a significant interaction between age and CRP, such that in younger children CRP was associated with shorter stature, but in older children was associated with greater stature (t = 2.15, P = 0.04, df = 109). CONCLUSIONS These results suggest that infection with helminths may have hidden costs associated with immunological changes, and that these costs may ultimately affect growth and other life history parameters.