IMMUNITY IN HUMANS TO NECATOR-AMERICANUS - IGE, PARASITE WEIGHT AND FECUNDITY

The effect of the humoral immune response on the weight and fecundity of the hookworm Necator americanus was examined in an endemically-infe cted human population. There was a highly significant negative correla tion between total IgE levels and parasite weight and fecundity, after controlling for any effects of host age and hookworm burden. This cor relation was present both at initial treatment and after 2 years' rein fection. There was a similar negative correlation between the number o f eosinophils and hookworm weight and fecundity at initial treatment. Correlations with levels of specific antibodies to N. americanus excre tory-secretory products were weaker and not significant, although ther e was a trend towards negative correlations with anti-ES IgE. This is the first field evidence for an effective human immune response to N. americanus. Although the mechanism of this effect is not clear, we sug gest that total IgE levels reflected the level of Th2 cell activation.