Microbial Autoimmunity

Infections may induce autoimmunity by different mechanisms including molecular mimicry, bystander activation, epitope spreading [1]. Living in dirtier environment seems to be protective towards the appearance of autoimmune diseases (hygiene hypothesis) [2]. Autoimmune diseases are at higher risk of infections due to immune dysregulation of the disease itself [3] and immunosuppressive therapy [4]. Chronic infections, especially from mycobacteria, may mimic autoimmune diseases [5,6,7]. The human microbiota may either, positively, or negatively, according to its composition, modulate the expression of autoimmune diseases [8]. Infections may induce a flare-up of a stabilized autoimmune disease, the interpretation of which represents a challenge for clinicians; in fact, it may be due to either the natural history of the disease itself or an infection, two conditions requiring different, rather opposite, therapeutical approaches [9].