The human hookworm pathogen Necator americanus induces apoptosis in T lymphocytes

In the present study, we demonstrate that Jurkat T cells undergo apoptosis when cocultured with the human hook-worm Necator americanus. Pro-apoptotic activity was dose-dependent and readily detectable in hookworm secretions. This pro-apoptotic effect appears to be specific to cells of T lineage since the monocytic cell line, THP-1, the erythroleukaemic cell line, K562, and the basophil cell line, KU812, were unaffected. The induction of apoptosis in Jurkat T cells by the hookworm secretions did not involve cell activation or the Fas/Fas ligand interaction. In addition, the pro-apoptotic effect of the hookworm, or its secretions, was observed with activated human T cells but not with resting peripheral blood lymphocytes. These findings support the hypothesis that the hookworms' ability to recurrently infect humans is due to the parasite creating a site of 'immune privilege' around itself. This strategy promptly induces any reactive host leucocytes infiltrating the site of parasite colonization to undergo apoptosis, which reduces inflammation and renders the infection relatively asymptomatic.