The therapeutic window of opportunity in rheumatoid arthritis (RA) is often referred to. However, some have questioned whether such a period, in which the disease is more susceptible to disease-modifying treatment, really exists. Observational studies are most frequently referenced as supporting evidence, but results of such studies are subject to confounding. In addition formal consensus on the definition of the term has never been reached. We first reviewed the literature to establish if there is agreement on the concept of the window of opportunity in terms of its time period and the outcomes influenced. Second, a systemic literature search was performed on the evidence of the benefit of early versus delayed treatment as provided by randomised clinical trials. We observed that the concept of the window of opportunity has changed with respect to timing and outcome since its first description 25 years ago. There is an ‘old definition’ pointing to the first 2 years after diagnosis with increased potential for disease-modifying treatment to prevent severe radiographic damage and disability. Strong evidence supports this concept. A ‘new definition’ presumes a therapeutic window in a pre-RA phase in which the biologic processes could be halted and RA development prevented by very early treatment. This definition is not supported by evidence, although is less well studied in trials. Some suggestions for future research in this area are made.

More intensive treatment strategies increased the chance for DMARD-free sustained remission, indicating that RA chronicity can be influenced. Patients with RA achieving DMARD-free sustained remission have a normalised functional status.

Autoreactive B cells mediate autoimmune pathology, but exactly how remains unknown. A hallmark of rheumatoid arthritis (RA), a common autoimmune disease, is the presence of disease-specific anticitrullinated protein antibodies (ACPAs). Here, we showed that ACPA-positive B cells in patients with RA strongly expressed T cell–stimulating ligands, produced abundant proinflammatory cytokines, and were proliferative while escaping inhibitory signals. This activated state was found at different degrees in different stages of disease: highest in patients with recent-onset RA, moderate in patients with established RA, and far less pronounced in ACPA-positive individuals “at risk” for developing disease. The activated autoreactive B cell response persisted in patients who achieved clinical remission with conventional treatment. ACPA-positive B cells in blood and synovial fluid secreted increased amounts of the chemoattractant interleukin-8, which attracted neutrophils, the most abundant immune cell in arthritic joints. Tetanus toxoid–specific B cells from the same patients exhibited properties of memory B cells without the activation and proliferation phenotype, but these cells transiently acquired a similar proliferative phenotype upon booster vaccination. Together, these data indicated that continuous antigenic triggering of autoreactive B cells occurs in human autoimmune disease and support the emerging concept of immunological activity that persists under treatment even in clinical remission, which may revise our current concept of treatment targets for future therapeutic interventions. In addition, our data pointed to a pathogenic role of ACPA-positive B cells in the inflammatory disease process underlying RA and favor approaches that aim at their antigen-specific inactivation or depletion.

This study is the first showing that ACPA-positive and ACPA-negative patients have clinical differences in the symptomatic phase preceding clinical arthritis. This contributes to the notion that ACPA-positive and ACPA-negative RA develop differently.

The use of a reference population resulted in a substantial reduction of false-positive results, without influencing the sensitivity. Although common for other tests in medicine, this phenomenon is novel for MRI in the early detection of RA.