A DISTINCT ROLE FOR INTERLEUKIN-13 IN TH2-CELL-MEDIATED IMMUNE-RESPONSES

Immune responses elicited by allergic reactions and parasitic worm inf ections are characterised by the induction of T helper 2 (Th2) cells, These cells secrete cytokines such as interleukin-4 (IL-4), IL-5 and I L-13, which induce the production of immunoglobulin E (IgE) and eosino phils [1,2], Previous studies using gastrointestinal nematodes to eluc idate 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 i n these responses, recent studies demonstrated that IL-4(-/-) mice exp el the parasitic gastrointestinal nematode Nippostrongylus brasiliensi s normally [4], suggesting that another T-cell mediator is required fo r efficient worm clearance, Using IL-13(-/-) mice, we have demonstrate d that, unlike wild-type and IL-4(-/-) mice, the IL-13(-/-) animals fa iled to clear N. brasiliensis infections efficiently, despite developi ng a robust Th2-like cytokine response to infection, Furthermore, trea tment of the IL-13(-/-) mice with exogenous IL-13 resulted in a reduct ion in the numbers of worms recovered, The IL-13(-/-) animals also fai led to generate the goblet cell hyperplasia that normally occurs coinc ident with worm expulsion, This observation may link IL-13 with the pr oduction of intestinal mucus which is believed to facilitate worm expu lsion, 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 redundan t. (C) Current Biology Ltd ISSN 0960-9822.