CD22 and CD72 cooperatively contribute to the development of the reverse Arthus reaction model

FcγRIIB inhibits inflammation in a murine model of psoriasis

BACKGROUND

Psoriasis is a chronic, inflammatory cutaneous disease. FcγRIIB is a low-affinity receptor for the IgG Fc fragment that provides a negative feedback pathway to down-regulate B-cell antigen receptor signaling.

OBJECTIVE

The aim of this study was to investigate the role of FcγRIIB in the development of murine imiquimod (IMQ)-induced, psoriasis-like skin inflammation.

METHODS

The experimental psoriasis-like skin inflammation was induced by the topical application of IMQ to the ears of FcγRIIB deficient (FcγRIIB^-/-) and wild-type (WT) mice. After 6 days, epidermal thickness and inflammatory cell infiltration of the skin were histopathologically assessed and cytokine and chemokine expression levels were measured with RT-PCR.

RESULTS

Skin inflammation was significantly worse in FcγRIIB^-/- mice than WT mice. In the skin, the numbers of Gr-1⁺ neutrophils, CD11c⁺ dendritic cells, and Foxp3⁺ T cells were significantly higher in FcγRIIB^-/- mice than WT mice. In the spleen, the numbers of CD25⁺Foxp3⁺ T cells and CD19⁺IL-10⁺ B cells were also significantly higher in FcγRIIB^-/-mice than WT mice. The mRNA expression of Il-6, Il-17a, and Il-23a was significantly enhanced in FcγRIIB^-/- mice. An adoptive transfer of splenic leukocytes from FcγRIIB^-/- mice into WT mice also exacerbated skin inflammation compared to WT mice that received splenic leukocytes from WT mice. Intravenous immunoglobulin significantly reduced skin inflammation in WT mice, but this improvement was not observed in FcγRIIB^-/- mice.

CONCLUSION

These results indicate that FcγRIIB likely plays a suppressive role in IMQ-induced, psoriasis-like skin inflammation. Furthermore, signal modulation via FcγRIIB is a potential therapeutic target for psoriasis.

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.

CD22 and CD72 contribute to the development of scleroderma in a murine model

BACKGROUND

Systemic sclerosis (SSc) is a systemic autoimmune disease that is characterized by excessive fibrosis. CD22 and CD72 are B cell-specific cell surface molecules that negatively regulate B cell function.

OBJECTIVE

The aim of the present study was to investigate the roles of CD22 and CD72 in a murine scleroderma model.

METHODS

The experimental fibrosis model was generated by subcutaneous injection of bleomycin or hypochlorous acid (HOCL) into wild-type (WT), CD22-deficient (CD22^-/-), CD72-deficient (CD72^-/-) and CD22 and CD72 double-deficient (CD22^-/-/CD72^-/-) mice. We histologically assessed skin fibrosis and inflammatory cell infiltration. Cytokine and chemokine expression levels were measured by real-time polymerase chain reaction.

RESULTS

The severity of fibrosis in the skin and lung was significantly less in CD22^-/-, CD72^-/-, and CD22^-/-/CD72^-/- mice than in WT mice in the bleomycin-induced model. In the skin of bleomycin-treated mice, the numbers of CD3⁺ T cells, CD8⁺ T cells, and F4/80⁺ macrophages were significantly lower in CD22^-/-, CD72^-/-, and CD22^-/-/CD72^-/- mice than in WT mice. The expression levels of mRNAs for IL-6, TNF-α, TGF-β, CTGF, IL-1β, IL-13, CXCL2, and ICAM-1 were significantly lower in CD22^-/-, CD72^-/-, and CD22^-/-/CD72^-/- mice than in WT mice. In the HOCL-induced model, both skin and lung fibrosis were ameliorated in CD22^-/-, CD72^-/- and CD22^-/-/CD72^-/- mice compared to WT mice.

CONCLUSION

These results indicate that CD22 and CD72 likely play crucial roles in skin and lung fibrosis. Moreover, the inhibition of CD22 and CD72 function has potential as a therapeutic approach to SSc.