Experimental hypersensitivity pneumonitis in Stim1^−/− chimeras. (A) Polymorphonuclear cell (PMN) migration in response to C5a and MIP-2 as measured in vitro by Transwell chemotaxis assays using PMN from bone marrow of the indicated mice. (B-F) IgG immune complex–induced lung injury was initiated in Stim1^+/+ (+/+) and Stim1^−/− (−/−) chimeric mice, and interstitial neutrophil influx in lung tissue was assessed by measuring MPO activity (B). Content of PMN (C), RBC (D), C5a-dependent bioactivity (E), and contents of MIP-2 and TNF-α (F) in BAL fluids were determined in samples obtained 5 hours after immune complex–induced pneumonitis. *P < .05 and **P < .001 compared with 0-hour controls. #P < .05 wild-type compared with Stim1^−/− 5-hour response. For each bar, n = 4 to 5 mice.