Xiap-deficient mice were unable to resolve the presence of curdlan. (A) Loss of body weight in Xiap^−/− mice with weekly treatment of curdlan. Female mice (8-12 weeks old) were primed with intraperitoneal administration of curdlan (5 mg/20 g body weight) every week, and body weight was determined; n = 13. (B) Attenuated inflammatory cytokine production in the Xiap^−/− mouse immediately after curdlan immunization. Serum was collected 2 hours after curdlan priming, and the quantity of IL-6, IL-12, MCP-1, and TNF-α was determined; n = 5. (C) Reduced recruitment of macrophages and neutrophils in the Xiap^−/− mouse. Peritoneal cavity infiltrates were collected 4 hours after curdlan priming, cell numbers were counted, and the population of macrophages and neutrophils was analyzed by flow cytometry. (D) Enhanced inflammatory cytokines secretion in Xiap^−/− mice 1 week after curdlan stimulation. Serum was collected from mice 1 week after immunization of curdlan, and the contents of cytokines were quantitated; n = 5. (E) Curdlan treatment leads to splenomegaly in Xiap^−/− mice. Spleens were isolated from control and Xiap^−/− mice 7 days after curdlan immunization for comparison. Sections of spleen were stained with hematoxylin and eosin. One representative pair (of 5 pairs) is shown. Bar indicates 50 μm. (F) Increased macrophage and neutrophil infiltration in Xiap^−/− mice 1 week after curdlan stimulation. Cells were harvested from the peritoneal cavity in mice from D, and the quantities of macrophages and neutrophils were determined. *P < .05, **P < .01, and ***P < .001 for paired Student t test.