Fig. 2.

P. copri RA-induced disease severity was promoted by a high-fiber diet. A Schematic of CIA mice with dietary intervention. B Confirmation of P. copri RA colonization by quantitative PCR. Control means P. copri genomic DNA; PC + FCD means DNA exacted from FCD group feces; PC + NCD means DNA exacted from NCD group feces. C Anti-bovine type II collagen IgG levels in the serum of PC + FCD (n = 4) or PC + NCD (n = 4) mice. D Clinical scores of collagen-induced arthritis. E Body weight of mice in the two groups. F Flow cytometric analysis of CD4⁺Th17⁺ cells in mesenteric lymph nodes. G Histological evaluation of the CIA colon and joint tissues. The scale bar is 100 μm. H The histology scores of the colon tissues. I The histology scores of the synovial tissues. Each symbol in (C, F, H, and I) represents an animal. P values were determined by two-way ANOVA (D, E), the Mann‒Whitney test (F, H, I), and Student’s t test (C). *p < 0.05, **p < 0.01, ****p < 0.0001. Abbreviations: PC P. copri RA, NCD non-fiber-containing diet, FCD fiber-containing diet