IL23A and Crohn ileitis: Enthesitis in GF-SKG mice was significantly less severe than in P.g. monoassociated SKG mice, highlighting the aggravating role of P.g. ASF-colonized SKG mice developed IL-23p19-dependent arthritis and enthesitis of similar relative intensity to P.g.-SKG mice but were protected from ileitis (Figure 1B and Figure 2, A–D).