Interleukin-4 receptor-Stat6 signaling in murine infections with a tissue-dwelling nematode parasite.

Interleukin-4 (IL-4) has been shown to be crucial in parasite expulsion in several gastrointestinal nematode infection models. Data from both epidemiological studies with humans and experimental infections in animals imply a critical role for the type II helper response, dominated by IL-4, in host protection. Here we utilized inbred mice on two distinct backgrounds to document the involvement of IL-4 in the clearance of a primary infection of Brugia from the murine host. Our data from infections of IL-4 receptor(-/-) and Stat6(-/-) mice further indicate that IL-4 exerts its effects by activating the Stat6 molecule in host target cells, a finding which links clearance requirements of a gastrointestinal tract-dwelling nematode with those of a tissue-dwelling nematode. Additionally, we show that the requirements for IL-4 receptor binding and Stat6 activation extend to accelerated clearance of a secondary infection as well. The data shown here, including analysis of cell populations at the site of infection and infection of immunoglobulin E (IgE)(-/-) mice, lead us to suggest that deficiencies in eosinophil recruitment and isotype switching to IgE production may be at least partially responsible for slower parasite clearance in the absence of IL-4.