IL6 and rheumatoid arthritis: Several authors reported an abundance of Prevotella copri (P. copri) in early RA patients [91,97] with a significant effect on the inflammatory response: an increase of related Th17 cytokines (i.e., IL-6, IL-23), an increased gut permeability with a major penetration of external antigens and bacteria, and a mutual decrease of protective species [98].