MODULATION OF THE ALLERGIC REACTIVITY OF SLUM CHILDREN BY HELMINTHIC INFECTION

Infection by helminthic parasites can cause the polyclonal stimulation of IgE synthesis, possibly via an enhanced production of interleukin- 4 (IL-4), and this has been suggested to influence the allergic reacti vity of tropical populations where these parasites are endemic. We eva luated a group of urban slum children in Caracas, Venezuela, with a hi gh prevalence of helminthic infection (70.8%), to establish the relati onship between the elevated IgE levels (3696 IU/ml) induced by these p arasites and various aspects of the allergic response. Although the ab solute levels of IL-4 detected in the sera of these children were low (0.65+/-0.20 ng/ml), a strong positive correlation (r = 0.78) was foun d between these and serum IgE. The cutaneous immediate hypersensitivit y reactivity to extracts of common environmental allergens was relativ ely low (17.5% to house dust), although that to Ascaris extract was mo derately high (49.4%). Significant inverse correlations were found bet ween total IgE levels and the different skin test reaction diameters, including Ascaris. The positivity of Prausnitz-Kustner passive transfe r tests was low in this group (34%), with a strong inverse correlation (r = - 0.75) being found between this and total IgE levels. Significa nt inverse correlations were also found between total IgE levels and s pecific IgE antibody to environmental allergens, and to Ascaris antige n. We suggest that the polyclonal production of IgE stimulated by helm inthic infection can suppress the allergic response to environmental a nd parasite allergens via both mast cell saturation and inhibition of specific IgE production.