A role for FcγRIIB in the development of murine bleomycin-induced fibrosis
Kaori Sawada1, Yasuhito Hamaguchi1, Kie Mizumaki1
1Department of Dermatology, Faculty of Medicine, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
Background:
Systemic sclerosis (SSc) is a systemic autoimmune disease characterized by excessive fibrosis. FcγRIIB is a low-affinity receptor for the Fc fragment of IgG. FcγRIIB is expressed on the surface of various leukocyte subsets and signals negative feedback pathways to down-regulate B-cell antigen receptor signaling.
Objective:
The aim of the present study was to investigate the role of FcγRIIB in the development of a murine bleomycin-induced scleroderma model.
Methods:
The experimental fibrosis model was generated by the intradermal injection of bleomycin into wild-type (WT) and FcγRIIB-deficient (FcγRIIB-/-) mice. We histologically assessed skin and lung fibrosis as well as inflammatory cell infiltration. Cytokine and chemokine expression levels were measured with RT-PCR.
Results:
The severity of fibrosis in the skin and lung was significantly worse in FcγRIIB-/- mice than in WT mice. In the skin of bleomycin-treated mice, the numbers of CD8+ T cells, F4/80+ macrophages, MPO+ neutrophils, NK1.1+NK cells, and B220+ B cells were significantly higher in FcγRIIB-/- mice than in WT mice. The expression of TNF-α and IL-1β was significantly higher in FcγRIIB-/- mice than in WT mice as was the expression of ICAM-1, CXCL2, and CCL3 in the affected skin. An adoptive transfer of splenic leukocytes from FcγRIIB-/- mice into WT mice showed exacerbated skin and lung fibrosis compared to WT mice without an adoptive transfer.
Conclusion:
These results indicate that FcγRIIB plays an inhibitory role in skin and lung fibrosis. Moreover, modulating FcγRIIB signaling has potential as a therapeutic approach for SSc.
