RAG1 and infection: To determine the impact of Toxoplasma infection on IL-33 expression and secretion, C57BL/6 WT and Rag1−/− mice were infected intraperitoneally (i.p.)with the Me49 strain or the replication-deficient CPS strain of T. gondii, and the levels of IL-33 at local sites of infection and affected tissues assessed by ELISA.