In addition to the HLA region, other loci associated with AIH susceptibility also exist, such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), a non-HLA susceptibility gene that has been widely studied in autoimmune diseases and is mainly expressed on the surface of regulatory and conventional T cells, inhibiting the response of autoreactive T cells [34]. This evidence concerns the gene CTLA4 and autoimmune hepatitis.