T cells are the main cell type expressing B7-1 and B7-2 in the central nervous system during acute, relapsing and chronic experimental autoimmune encephalomyelitis

T cell co-stimulation through the CD28 receptor on T cells is critical to t he induction of experimental autoimmune encephalomyelitis (EAE). In this st udy, expression of the cc-stimulatory ligands B7-1 (CD80) and B7-2 (CD86), as well as the receptors CD28 and CTLA-4, were quantitated in central nervo us system (CNS) tissues from mice at various stages of EAE. Immunohistochem istry and flow cytometry of CNS-infiltrating cells revealed a high percenta ge of infiltrating T cells expressing B7-1 and B7-2 during acute, chronic a nd relapsing EAE. Of the infiltrating cells 10-20 % were CTLA-4(+), most of which were CD4(+) T cells. B7-1 and B7-2 expression within the CNS during active EAE might increase the potential for local activation of autoimmune T cells; however, the high level of expression of B7 molecules may also pro vide a mechanism for the autoregulation of activated CTLA-4(+) T cells.