Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that primarily affects joints. The several mechanisms involved in the development of the disease are not completely understood. It has been proposed that different environmental factors, such as cigarette smoking, occupational and atmospheric agents act as trigger stimuli for the development of RA in genetically predisposed individuals, leading to synovial hyperplasia and bone destruction. The initial disease stage of RA is associated with alteration of innate and adaptive immune system with consequent production of autoantibodies, targeting various molecules including modified self-epitopes. In the following stages of the disease, both the innate (e.g. dendritic cells, macrophages and neutrophils) and adaptive immune cells (e.g. B and T lymphocytes) contribute to the amplification and perpetuation of the chronic inflammatory state. The recognition of key cells, mediators and mechanisms implicated in the pathogenesis of RA could provide the basis for the development of new and precise disease-modifying anti-rheumatic drugs. Therefore, we reviewed the literature of the last year in order to find the new insights in RA pathogenesis.