The aims of the present study were to detect antibodies against lysine-containing lipopolysaccharides of P. mirabilis and its synthetic oligosaccharide fragments in the sera of patients with rheumatic diseases, and to correlate the serological response between LPSs and rheumatic and inflammation markers [RF, ACPA, C- reactive protein (CRP), and erythrocyte sedimentation rate (ESR)]. The gene discussed is PRTN3; the disease is rheumatic disorder.