CD80CD86 deficiency disrupts regulatory CD4+FoxP3+T cell homoeostasis and induces autoimmune-like alopecia

Alopecia areata (AA) is an autoimmune disease that results in spot baldness in humans. Adequate animal models for AA are currently lacking. The objective of this study was to elucidate the mechanism of autoimmune-like alopecia (ALA) in C57BL/6.CD80CD86-deficient (B6.CD80CD86^-/- ) mice. Incidence and severity of alopecia were analysed in 58 B6.CD80CD86^-/- mice using histological examination, flow cytometry, multiplex enzyme-linked immunosorbent assay, quantitative RT-PCR and CD25 inhibition test. Both male and female B6.CD80CD86^-/- mice showed almost 100% incidence of hair loss at 40 weeks of age. Moreover, CD4+FoxP3+Treg (Treg) cell population in B6.CD80CD86^-/- mice was significantly lower than in B6 mice, which presumably underlined autoimmune reaction. Histologically, B6.CD80CD86^-/- mice showed CD4+ and CD8+ T-cell infiltration around terminal follicle region and exhibited hair follicle destruction in the anagen or catagen stage. Negative correlation between the number of CD4+FoxP3+ Tregs and ALA was confirmed by the CD25 depletion test in B6 mice, as follicle destruction was similar to that observed in B6.CD80CD86^-/- animals. CD80CD86 deficiency disrupted CD4+FoxP3+ Treg homoeostasis and prompted the development of ALA. We demonstrated that B6.CD80CD86^-/- mice might have several advantages as an ALA model, because they exhibited high incidence of disease phenotype and epipathogenesis similar to that observed in human AA.