Although the present understanding of the immunopathogenesis of rheumatoid inflammation is still incomplete, there is substantial evidence that effector CD4+ T helper (Th) cells play a central role.
In recent years, in addition to the established Th cell subsets Th1 and Th2 cells, other subsets, such as Th9, Th17, Th22 and T follicular helper (Tfh) cells have been described. Defining the contribution of T cells in the initiation and maintenance of inflammation has been augmented by the identification of functionally distinct subsets of effector Th cells that can be classified based on their cytokine and transcription factor profiles.
Increasing knowledge of the role of these various T cell populations in chronic inflammation provides a better understanding and insights into the pathogenic mechanisms and chronification of rheumatic diseases.