CCL26 regulates the proportion of [CD4.sup.+][CD25.sup.+][FOXP3.sup.+] Tregs and the production of inflammatory factors in peripheral blood mononuclear cells following acute ischemic stroke via the STAT5 pathway

Acute ischemic stroke (AIS) is the most common type of stroke. Recent studies have found that AIS is closely involved in the immune regulation function of regulatory T cells (Tregs). C-C motif chemokine ligand 26 (CCL26) is a member of the chemokine family that plays an essential role in cell activation, cell differentiation, lymphocyte homing, and inflammatory and immune responses. The present study aimed to investigate the role of CCL26 in the regulation of Tregs in AIS. Peripheral blood mononuclear cells (PBMCs) were incubated with a CCL26-neutralizing antibody. The proportion of cluster of differentiation [(CD)4.sup.+][CD25.sup.+] forkhead box P3 [(FOXP3).sup.+] Tregs was increased, and the expression of FOXP3, phosphorylated signal transducer and activator of transcription 5 (p-STAT5), and that of the immunosuppressive factors, interleukin (IL)-10 and transforming growth factor (TGF)-[beta]1, was upregulated. Conversely, the expression of immune-promoting factors, such as tumor necrosis factor (TNF)-[alpha] and IL-6 was significantly downregulated. Further experiments using CCL26 recombinant protein-treated PBMCs revealed a decreased proportion of [CD4.sup.+][CD25.sup.+][FOXP3.sup.+] Tregs and the downregulated expression of FOXP3, p-STAT5, TGF-[beta]1 and IL-10. Moreover, the expression of immunostimulatory factors, such as CX3C chemokine receptor 1, TNF-[alpha] and IL-6 was significantly upregulated. On the whole, these results demonstrate that CCL26 regulates the proportion of [CD4.sup.+][CD25.sup.+][FOXP3.sup.+] Tregs and the production of inflammatory factors in PBMCs following AIS via the STAT5 pathway. Key words: acute ischemic stroke, C-C motif chemokine ligand 26, regulatory T cells, signal transducer and activator of transcription 5