As some factors associated with the tropical environment can modify the expression of atopie disease, various indicators of allergic reactivity were compared between allergic and non-allergic subjects of different socio-economic level in Caracas, Venezuela (Lat. 10°N). The socio-economic levels considered were high (HSEL), medium-high (MSEL) or low (LSEL). As generally found in temperature climates, in the HSEL the total serum IgE levels of allergic patients were significantly greater than those of nonallergic individuals (geometric means of 274 vs 126 IU/ml, respectively), as were also the specific serum IgE antibody levels (55-6 vs 23-8% positive, respectively, for house dust). These results correlated closely with the skin-test reactivity of these subjects (60-3 vs 17-5% positive for house dust). In this group, the degree of intestinal helminthic infection was low (5-6% positive for Ascaris). In contrast, for the MSEL where the degree of parasitic infection was higher (13-0%), the total serum IgE levels were elevated in both allergic and non-allergic subjects (602 vs 363 IU/ml). Similarly, positivity for specific IgE antibody was high, and comparable between allergies and non-allergies of this group (61-5 vs 54-2%), as was also the case for skin-test reactivity (71-9 vs 60-4%). In the LSEL, parasitic infection was prevalent (47-6%), and the total serum IgE levels were markedly elevated, with little difference occurring between allergic and non-allergic individuals (2269 vs 1981 IU/ml). The positivity for specific IgE antibody was high, and effectively independent of the allergic state (75-6 vs 53-7%), but in contrast the skin test reactivity was relatively low (22-0 vs 9-8%). The lack of correlation between skin test and specific IgE results in this group appeared to have Correspondence: Dr Neil R. Lynch, Instituto de Biomedicina, Aptdo. 4043, Caracas lOlOA, Venezuela. N. R. Lynch et al. two causes. Firstly, although the frequency of positivity in specific IgE was high, only low grade antibody activity was detected. Secondly, studies ofskin reactivity indicated that some form of interference to target cell sensitization was occurring. The possible participation of helminth-induced polyclonally-increased IgE synthesis in the modification of allergic reactivity is discussed.
