Abstract
CD4+Foxp3+ T regulatory (Treg) cells provide a key defence against inflammatory disease, but also have an ability to produce pro-inflammatory cytokines. The evidence for these two possibilities in multiple sclerosis (MS) is controversial. However, this has largely been based on studies of circulating Treg cells derived from peripheral blood, rather than the central nervous system. We show that Foxp3+ cells in the brains of MS patients predominantly produce interleukin-10 (IL-10) and show high expression of the IL-33 receptor ST2 (associated with potent Treg function), indicating that Treg in the inflamed brain maintain their suppressive function.