Allergic Reactivity of Children of Different Socioeconomic Levels in Tropical Populations

Abstract

Widely variable prevalences of allergic diseases have been reported in tropical populations, and this has been suggested to be due to effects of the nonspecific polyclonal stimulation of IgE synthesis caused by the helminthic infections that are endemic in these areas. Since 1980, we have been evaluating the allergic reactivity of different socioeconomic sectors of the population of tropical Venezuela (lat. 2–12°N), and in the present study analyze the overall results obtained in the laboratory evaluation of children (5–15 years of age) belonging to these groups. Children of medium-high socioeconomic level (M-HSEL), who experience occasional helminthic infections, have moderately high total serum IgE levels, and have elevated skin test positivities and specific IgE levels against environmental allergens. Persons of low socioeconomic level, in the urban, and particularly rural situation experience frequent helminthic infection, and have highly elevated total serum IgE levels. In contrast to the M-HSEL, the majority of these children have detectable specific IgE antibody against a variety of inhalant allergens, but relatively few have high levels, and their skin test positivity is also low. In these frequently parasitized persons, evidence of saturation of mast cell Fcε receptors was found by tests of passive sensitization. We propose, therefore, that helminthic parasites have a biphasic effect on allergic reactivity; occasional infections are stimulatory, via their nonspecific potentiation of IgE synthesis against environmental allergens, and frequent infections are suppressive due to the widely polyclonal stimulation that they cause, resulting in both diminished specific antibody production against any given allergen and mast cell Fcε receptor saturation.

Relationship between allergic manifestations and Toxocara seropositivity: a cross-sectional study among elementary school children

“…Our results are in agreement with the observations of HAGEL et al [29] from a study performed in Venezuela. They observed that rural children with low socioeconomic background had a high and diverse parasite burden, and that urban children from medium to high socioeconomic backgrounds had a low and less diverse parasite burden.…”

<i>Toxocara</i> Infection Seroprevalence and Its Relationship with Atopic Features in a General Adult Population

“…Much of the apparent controversy in the association of helminthiasis with atopic features may be due to (1) the extrapolation of data derived from animal models (which frequently use human parasites in nonpermissive rodent hosts), (2) the lack of distinction between natural and zoonotic infections (which frequently induce a powerful destructive response that often results in elimination of parasites), (3) the nature of helminths (able or unable to develop tissue-dwelling stages), and (4) the burden of infection [2]. Low-grade/occasional helminth infections (typical of industrialized countries) are stimulatory of allergic reactivity, whereas high-grade/frequent infections (typical of developing countries) are suppressive [10, 45, 46]. In the present population from a theoretically industrialized country, we found a positive association between some atopic features and exposure to Toxocara , a zoonotic tissue-dwelling parasite which, as an exception, is able to establish long-lasting infections after a fine interaction with the host’s immune system [2,24,25,26, 42].…”

In vivo Biological Activity of Recombinant <i>Der </i><i>p</i> II Allergen of House-Dust Mite

“…In addition, 40% of the IgE antibody against WME was directed against r Derp II in the sera of subjects who were skin test positive to both allergen preparations. House dust is the major source of allergenic activity in the tropics [23,24], and for this reason the ad vantages that recombinant mite allergens could eventually offer over conventional mite cultures, in terms of quantity and cost, are particularly important.…”