CD80 and infection: Previous studies demonstrate that human B cells isolated from peripheral blood may be activated and the expression levels of CD80, CD86, MHC classes I and II molecules on the cell surface is efficiently up-regulated by infection with Epstein-Barr virus or co-culture with mitogen-induced cells transfected with the human CD40L [16,17], and the B cells may serve as APCs and induce specific CTLs.