In early studies, it was shown that the propensity of IL-10-deficient mice to develop colitis (exacerbated by administration of the nonsteroidal anti-inflammatory drug piroxicam) was ameliorated by H. polygyrus infection (42), and the same protective effect was observed when transferring IL-10-deficient T cells to RAG-deficient mice, which normally develop severe colitis (115). Here, IL10 is linked to colitis.