In the last two decades, more and more light has been shed on the immunologic pathogenesis of autoimmune liver diseases, notably autoimmune hepatitis (AIH). An immunologic dysbalance with proinflammatory immune responses dominating over hepatic tolerance seems to be part of AIH pathogenesis. In detail, an impairment of regulatory T cells (Treg) is suspected. If this holds true and reduced Treg numbers or their function are pathogenic for AIH, this offers the option of cellular or immunomodulatory therapy. However, the exact immunological role of Treg in AIH still needs to be clarified before cellular therapy is promising for patients.