One year in review 2017: pathogenesis of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease influenced by both genetic and environmental factors. It has been postulated that a high-risk genetic background, in combination with epigenetic marks and environmental exposures, leads to a cascade of events inducing synovitis and consequent destructive arthritis. The clinical picture of joint involvement in RA is the result of chronic inflammation of the synovium, characterised by interactions of resident cells such as fibroblast-like synoviocytes (FLS) with cells of the innate (e.g. macrophages, dendritic cells, mast cells and NK cells, neutrophils) and adaptive immune system (e.g. B and T lymphocytes). Currently, our understanding of the role of innate and adaptive immunity in the pathogenesis of RA is expanding. The concept of how immune responses contribute to the disease has dramatically evolved over the last 50 years. Shedding some light on the different aspects of RA pathogenesis will help to identify new targets for the development of disease-modifying therapies. Thus, in this review we report new insights in RA pathogenesis, resulting from a literature research date published in the last year.