Expression of AIRE transcription factor in human lymph nodes and ectopic lymphoid structures: relationship with tissue micro-architecture.

The autoimmune regulator (AIRE) is a transcription factor constitutively expressed in primary lymphoid organs (the thymus) and physiologically involved in the mechanisms of central tolerance in the developing T cell repertoire. Recent studies have described the expression of AIRE in lymph nodes, although its precise distribution and function in the periphery remain only partly clarified. The primary aim of the current study was to characterize and quantify the expression of AIRE across the spectrum of secondary and ectopic lymphoid tissues in humans, focusing on its relationship with local micro-architecture and inflammatory status. We demonstrated the existence of variable levels of AIRE expression in human normal lymph nodes, with positive cell localization both in the T cell compartment and specific B cell-rich areas within reactive sites. The analysis of control- and rheumatoid-synovial tissues enriched in lymphoid structures highlighted the possible (thought selective) ectopic induction of the transcription factor in inflamed peripheral tissues of patients with chronic autoimmune diseases.