A recent study showed shared sequences between Collinsella and DRB1*0401, suggesting that Collinsella might contribute to RA via molecular mimicry [8], further supporting the current observations that HLA class II molecules can present self-HLA-derived peptides [35] and mimicry with a pathogen can result in enhanced stimulation and inflammation in certain conditions. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.