Up-regulation and pathogenic roles of CCL18-CCR8 axis in IgG4-related disease.

Objectives: To determine the protein expression level, expressing cell types, and pathogenic roles of chemokine (C-C motif) ligand 18 (CCL18) and its receptor chemokine (C-C motif) receptor 8 (CCR8) in affected tissues of patients with IgG4-related disease (IgG4-RD). Methods: The protein expression levels of CCL18 in labial salivary glands (LSGs) assessed by immunofluorescence (IF) staining were compared among patients with IgG4-RD (n = 3), primary Sjogren's syndrome (pSS; n = 4), and control subjects (n = 5). CCL18 expression levels in macrophages, CD11c(+) cells, B cells, and plasmacytes in LSGs were examined by double IF staining. The protein expression levels of CCR8 and expressing cells (T, B cells, and plasmacytes) in LSGs were also compared among patients with IgG4-RD, pSS, and control subjects by double IF staining. The effects of the CCL18-CCR8 axis on total IgG, IgG2, and IgG4 production by peripheral blood mononuclear cells (PBMCs) stimulated with CD40L, IL-4, IL-10, and IL-21 were examined by in vitro assays. Results: CCL18 was specifically upregulated in LSGs of patients with IgG4-RD, compared with only a few cells in pSS patients and none of the controls. The numbers of CCL18-producing macrophages, CD11c(+) cells, and plasmacytes in LSGs were significantly higher in IgG4-RD patients than in pSS patients and control (p < .05, each). Many T and B cells and some plasmacytes expressed CCR8 in LSGs of IgG4-RD and pSS patients. CCL18 specifically enhanced IgG4 production by stimulated PBMCs. Conclusion: CCL18-CCR8 axis was upregulated in LSGs of patients with IgG4-RD, suggesting possible roles of this axis in the pathogenesis of IgG4-RD.Key messages The CCL18-CCR8 axis in labial salivary glands (LSGs) and lacrimal glands of IgG4-RD patients was specifically upregulated compared with primary Sjogren's syndrome and control subjects. This axis might be a potentially novel therapeutic target in IgG4-RD, based on its important etiopathogenic roles, such as chemotaxis of various cells, induction of fibrosis, and enhancement of IgG4 production.