However, we and others have previously shown that ACPA levels associate with increased titers of antibodies to P. gingivalis in people at risk for RA [24,47], as do antibodies to Prevotella in RA [48], and that antibody titers to leukotoxin A are increased in ACPA-positive at-risk individuals [43,49]. Here, PRTN3 is linked to rheumatoid arthritis.