Lymphoid tissue reactions in rheumatoid arthritis.

Frequently, the immune cell infiltrate of chronically inflamed tissues develops functional germinal centres and acquires structural features of secondary lymphoid organs. Ectopic lymphoid structures occur in peripheral tissues not only during autoimmune diseases but also in tumors (reactive infiltrate), chronic infections and graft rejection, indicating a strong link between lymphoid neogenesis and persistent antigen driven immune/inflammatory responses. There has been a renewed interest in ectopic lymphoid neogenesis, as better understanding of the mechanisms underpinning this process could contribute to elucidate the bio-pathological mechanisms involved in transition from acute-self resolving to chronic immunological aggression as well as identify novel therapeutic targets. Here we critically review recent clinical and biological studies addressing the role of ectopic lymphoid neogenesis specifically in rheumatoid arthritis.