CRP and rheumatoid arthritis: The C-reactive protein, rheumatoid factor levels, disease progression, and MTX therapy positively correlated with beta-diversity in RA patients, suggesting that the treatment may affect the interactions between microbiota and mucosal immune cells in the gut, and supporting the hypothesis that gut microbes and their metabolities may interfere in the clinical response to disease-modifying antirheumatic drugs (DMARDs) [19,20].