Fig. 5

a C5a levels in serum from patients with rheumatoid arthritis (RA) and healthy control patients were measured by enzyme-linked immunosorbent assay (ELISA) (healthy, n = 8; patients with RA, n = 40). b, c Relationship between C5a levels and C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) in the serum from patients with RA. d–h C5a levels and antibody titers to periodontal pathogens (Porphyromonas gingivalis W83, Prevotella intermedia, Treponema denticola, Tannerella forsythia, and Aggregatibactor actinomyvetemcomitance) in serum from patients with RA were measured by ELISA. Bars show median of the data. Statistical analyses were performed by using Mann–Whitney U test and Pearson’s correlation coefficient (*P <0.05). Abbreviation: NS not significant