Ankylosing​ ​spondylitis​ ​(AS)​ ​is​ ​a​ ​chronic​ ​inflammatory​ ​disorder​ ​in​ ​which​ ​aberrant immune​ ​responses​ ​to​ ​the​ ​intestinal​ ​microbiota​ ​are​ ​thought​ ​to​ ​drive​pathogenesis.​ ​The​ ​HLA-B27 transgenic​ ​rat​ ​is​ ​a​ ​foremost​ ​translational​ ​model​ ​of​ ​disease,​ ​with​ ​rats​ ​expressing​ ​the​ ​major human​ ​risk​ ​allele​ ​for​ ​AS.​ ​We​ ​have​ ​shown​ ​previously​ ​the​ ​IgA​ ​response​ ​to​ ​gut​ ​microbes​ ​is strongly​ ​elevated​ ​in​ ​this​ ​model,​ ​but​ ​the​ ​specificity​ ​of​ ​this​ ​response​ ​remains​ ​unclear.​ ​Here​ ​we used​ ​the​ ​novel​ ​IgA-SEQ​ ​technique​ ​to​ ​test​ ​the​ hypothesis​ ​that​ ​HLA-B27​ ​expression​ ​alters​ ​the microbial​ ​repertoire​ ​of​ ​the​ ​intestinal​ ​IgA​ ​response.