Elevated frequencies of CD4+ IL-21+T, CD4+ IL-21R+T and IL-21+Th17 cells, and increased levels of IL-21 in bleomycin-induced mice may be associated with dermal and pulmonary inflammation and fibrosis.

Aim Systemic sclerosis ( SSc) is characterized by immune abnormalities, progressive fibrosis of the skin and internal organs, and microvascular injury and damage. Interleukin-21 receptor ( IL-21R) is expressed in the epidermis from patients with SSc. However, information describing the role of IL-21 in SSc is limited. Methods We established a mouse model of bleomycin ( BLM)-induced fibrosis. The frequency of CD4+ IL-21+T, CD4+ IL-21R+T and IL-21+Th17 cells in peripheral blood, skin and lungs of BLM-induced mice were detected by flow cytometry; IL-21 levels in the peripheral blood were evaluated by enzyme-linked immunosorbent assay ( ELISA). CD4+T cells were isolated from the spleen of BLM-induced and control mice and cultured in vitro alone or in the presence of mr IL-21 or mr IL-21 plus transforming growth factor ( TGF)-β1. The frequency of Th17 cells was detected by flow cytometry; levels of IL-17 were evaluated by ELISA, and the expression of IL-17A and retinoic-acid-receptor-related orphan receptors gamma t ( RORγt) messenger RNA were analyzed by real-time polymerase chain reaction. Results Compared to control mice, the frequency of CD4+ IL-21+T, CD4+21R+T and IL-21+Th17 cells and the levels of IL-21 were significantly increased in BLM-induced mice. The frequency of CD4+ IL-21+T, CD4+21R+T and IL-21+Th17 cells and the levels of IL-21 were correlated with dermal and pulmonary inflammation and fibrosis. In vitro analyses indicate that IL-21 promoted the differentiation of Th17 cells from CD4+ cells isolated from the spleen of BLM-induced mice. Conclusion IL-21 may play an important role in the pathogenesis of SSc as a Th17 effector cytokine, and IL-21 may induce the differentiation of Th17 cells in the BLM-induced SSc mouse model. [ABSTRACT FROM AUTHOR]