LRRK2 G2019S transgenic rats show:• Decreased numbers of bone marrow myeloid progenitors;• Decreased numbers of Th17 cells in the colon, but not in the brain, during TNBS- or DSS-induced colitis or LPS-induced systemic inflammation;• Myeloid cells defective in supporting Th17 cell differentiation in vitro. The gene discussed is LRRK2; the disease is inflammation.