A role for FcγRIIB in the development of murine bleomycin-induced fibrosis.

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.