CP-690,550 inhibits the increase in bone marrow myeloid precursors in the rat AIA model. Bone marrow from normal and AIA rats (n = 12 rats per group) was analyzed for maturing myeloid precursors by flow cytometry at day 7 and day 21 post-adjuvant immunization (A). (*) indicates statistical significance p ≤ 0.0008 compared to normal animals. AIA rats were treated with CP-690,550 or vehicle control orally, once daily, days 14 to 21, and bone marrow was collected and analyzed on day 21 for maturing myeloid cells by flow cytometry (B). (*) indicates statistical significance p ≤ 0.05 compared to the disease vehicle control. Data represented as the mean ± SEM.