M-CSF-Stimulated CD11b+ Myeloid Cells Induce Alopecia Areata in C3H/HeJ Mice

Abstract Alopecia areata (AA) is a T cell-mediated autoimmune skin disease with clinical features of hair loss and skin inflammation. It is unclear whether other immune cells except T lymphocytes are also involved in the development of AA. Here, our results reveal that dermal injection of either CD11b+ myeloid cells isolated from AA-affected skin or non-AA splenocyte-derived CD11b+ cells treated with macrophage colony-stimulating factor (M-CSF) induces AA in C3H/HeJ mice. The functional similarity of these cells in induction of AA seems to be due to a higher expression of M-CSF in AA affected skin. To explore the mechanism by which dermal injection of CD11b+ cells induce AA, we co-culture either AA derived skin cells or M-CSF-stimulated CD11b+ cells with naïve splenocytes. The results of splenocyte proliferation assay and immunoglobulin release in conditioned medium show a significant increase of splenocyte proliferation and IgG level in conditioned medium under both conditions as compared to controls. Most activated splenocytes induced by M-CSF-stimulated myeloid cells are B lymphocytes. B cell activation are further confirmed in AA-affected skin and skin draining lymph nodes of AA mice. In conclusion, in this study, we have provided evidence that M-CSF stimulated CD11b+ cells are able to induce AA in C3H/HeJ mice through a possible mechanism by activating B lymphocytes. This finding may provide insight for understanding the pathogenesis of AA.