Genetic deletion of Syk during active disease prevents pathogenic pulmonary function. Mice were transplanted with either WT or Syk fl/fl × ERT2-Cre BM. On day 8, mice were treated with tamoxifen for 5 days to delete Syk in donor-BM–derived cells. Pulmonary function tests of mice on day 60. *P < .5; ** P < .01. Error bars represent SEM; n = 10 per group.