FX1-treated B6 Rag1-/- mice displayed more severe Lyme arthritis than vehicle-treated control B6 Rag1-/- mice indicating that BCL6 expression in non-lymphocytes, such as myeloid cells, is critical for the increased arthritis severity observed upon FX1 treatment (Fig 9G and 9J). Here, RAG1 is linked to arthritic joint disease.