A distinct role for interleukin-13 in Th2-cell-mediated immune responses

Immune responses elicited by allergic reactions and parasitic worm infections are characterised by the induction of T helper 2 (Th2) cells, These cells secrete cytokines such as interleukin-4 (IL-4), IL-5 and IL-13, which induce the production of immunoglobulin E (IgE) and eosinophils [1,2], Previous studies using gastrointestinal nematodes to elucidate the role of Th2-cell-mediated immune responses have demonstrated a causal relationship between T cells and worm expulsion (reviewed in [3]). Although it has been proposed that IL-4 played a central role in these responses, recent studies demonstrated that IL-4(-/-) mice expel the parasitic gastrointestinal nematode Nippostrongylus brasiliensis normally [4], suggesting that another T-cell mediator is required for efficient worm clearance, Using IL-13(-/-) mice, we have demonstrated that, unlike wild-type and IL-4(-/-) mice, the IL-13(-/-) animals failed to clear N. brasiliensis infections efficiently, despite developing a robust Th2-like cytokine response to infection, Furthermore, treatment of the IL-13(-/-) mice with exogenous IL-13 resulted in a reduction in the numbers of worms recovered, The IL-13(-/-) animals also failed to generate the goblet cell hyperplasia that normally occurs coincident with worm expulsion, This observation may link IL-13 with the production of intestinal mucus which is believed to facilitate worm expulsion, These data support a unique role for IL-13 in Th2-cell-mediated immune responses and demonstrate that IL-13 and IL-4 are not redundant. (C) Current Biology Ltd ISSN 0960-9822.