The evolutionary context of chronic allergic conditions

Abstract

The question of why populations with ecologies that resemble our evolutionary past rarely experience allergic conditions such as asthma has intrigued many biomedical scientists. Here we present descriptive data on the ecological context of allergic sensitization among the Hiwi of southwestern Venezuela and suggest reasons for why this and other lowland South American Indian groups do not express the allergic response at levels seen in industrialized contexts. Allergic sensitization among the Hiwi appears to be negligible. This absence occurs in the context of high exposure to macroparasites (mainly hookworm), nutritional stress, frequent and prolonged breastfeeding, low indoor allergen deposition, and few hours spent per day indoors. We conclude that seeking unidimensional answers to the question of why isolated human groups generally experience few allergic conditions is potentially flawed because allergies are produced by a multifaceted immunoglobulin E (IgE) system that responds in complex ways to the environmental and behavioral exposures we examined. Instead, we propose a general model of physiological trade-offs in energy allocation between production of IgE of undefined specificity and production of allergen-specific IgE. In addition, we consider the simultaneous effects that exposures such as nutritional stress, allergen exposure, and breastfeeding may have on these trade-offs.

Longitudinal study of tuberculosis outcomes among immunologically naive Aché natives of Paraguay

“…Interactions between environmental and genetic factors probably give rise to this unique indigenous immune defense profile. An important environmental stimulus of Th2 responses is helminthic infection, which is endemic and ubiquitous among them (Salzano and Callagheri‐Jacques, 1988; Hurtado et al, 1997). However, nonindigenous populations with helminthic infection rates as high as those observed among South American Indians do not overproduce IgE to the same extent (Lynch et al, 1993).…”

Gender and the hygiene hypothesis

“…Researching allergies among the Hiwi settlements of Venezuela, anthropologists Hurtado, et al noted that, consistent with the hygiene hypothesis, these populations had lower rates of allergies than are typically found in populations of the industrialized nations of the North and West (Hurtado, Hill, Arenas de Hurtado, & Rodriguez, 1997). They also note that Hiwi girls spend significantly more time than do boys engaging in "grooming behaviors," and that these behaviors "serve to eliminate ectoparasites" (p. 63).…”

The Ecologies of Human Immune Function

“…Support for this "hygiene hypothesis" comes from a number of studies reporting that infectious morbidity early in life is associated with increases in Th2 cytokine production, IgE concentration, and symptoms of allergy and asthma later in life (Matricardi et al 2000, McDade et al 2004b, Shirakawa et al 1997 (Figure 4). In contrast, populations characterized by chronic helminthic infection also produce high concentrations of Th2 cytokines and IgE but do not suffer from allergy or asthma (Hurtado et al 1997, Yazdanbakhsh et al 2002. In these cases, chronic pathogen Relationship between infectious morbidity in the first 6 months of life and total IgE concentration at age 14-15 years in the Philippines.…”