Characterization of target antigens from anti-neutrophil cytoplasmic antibodies in autoimmune hepatitis type-I.

The occurrence of anti-neutrophil cytoplasmic antibodies (ANCA) has been described in sera of patients with autoimmune hepatitis (AIH). The significance of this finding remains uncertain and the nature of the target antigen(s) has not yet been defined. We studied 32 sera from patients with AIH type-I and prepared extracts of human neutrophils to identify the target antigen(s). A 43 kDa dominant immunoreactive protein was found and identified as the cytoskeletal component actin. Initial studies to define the antigenic determinants identified three different actin domains.