In this present study, the SKG mice were bread in the vivarium of Hiroshima University contrast to the former study that used SKG mice bred in Japan Clea corp [16]., although some discrepancy in the productions of serum IL-6 between present and former of our study using SKG RA mouse model may be attributed to the distinct microbiomes established in the mice at two different facilities. Here, IL6 is linked to rheumatoid arthritis.