Fig. 5

Deregulated miRNAs in RA that affect the Th17/Treg ratio. One of the central events in RA pathology is the imbalance between Th17 cells and Tregs. In the context of RA, activated APCs capture and process autoantigens for subsequent presentation to naïve CD4⁺ T cells, which provokes CD4⁺ T-cell activation and differentiation. The differentiation and expansion of Th17 cells are enhanced, leading to overwhelming inflammation via excessive inflammatory cytokine (for example, IL-17) release. In parallel, the Treg proportion is decreased, and the suppressive properties of Tregs are impaired, which is correlated with disrupted immune homeostasis. A consequent increase in the Th17/Treg ratio accelerates RA progression. The differential expression of several miRNAs changes the frequency and function of Th17 cells (red box) and/or Tregs (green box), thereby promoting the pathogenic role of these cells in RA. miRNA microRNA, RA rheumatoid arthritis, Th17 cell T helper 17 cell, Treg regulatory T cell, APC antigen-presenting cell