Given that young sPLA2-IIATGN mice are more susceptible to K/B×N serum–transferred arthritis (35, 86, 87) and that the microbiota can contribute to RA (88), we investigated the susceptibility to inflammatory arthritis of 12-week-old sPLA2-IIATGN mice either conventionally colonized or treated with antibiotics to deplete microbiota. The gene discussed is PLA2G2A; the disease is rheumatoid arthritis.