Tang Y et al. – In this study, the authors co–cultured rheumatoid arthritis fibroblast–like synoviocytes (RA–FLS) with or without anti–cluster of differentiation (CD)3/CD28–stimulated peripheral blood mononuclear cells (PBMCs) to investigate if this combination has immunoregulatory effects on peripheral circulating T follicular helper (Tfh) cells. The results of the study showed that this co–culture increased the number of CD4 + chemokine receptor type 5 (CXCR5) + inducible T–cell co–stimulator (ICOS) + T cells of RA PBMC via interleukin (IL)–6, which is an important cytokine involved in the differentiation of Tfh cells. The production of these cells was decreased when production of reactive oxygen species was inhibited using N–acetyl–L–cysteine and blocking of tumor necrosis factor receptor 2 and IL–1? receptor. Thus, the study revealed a novel mechanistic insight into the participation of RA–FLS and PBMC interaction in the pathogenesis of RA and provided support for the use of biologics for RA.