Antibodies to cytokeratin filaments in patients with alcoholic liver disease

Anti-cytokeratin antibodies in sera of the patients with autoimmune hepatitis

Antibodies to cytokeratin (CK) are found in some patients with autoimmune hepatitis (AIH). We hypothesized that serum antibodies to CK8, CK18 and CK19 may be formed in patients with AIH. We established an enzyme-linked immunosorbent assay (ELISA) to quantify anti-CK8, anti-CK18 and anti-CK19 antibodies in sera of patients with AIH. In addition, we quantified circulating CK8:anti-CK8 antibody as well as CK18:anti-CK18 antibody immune complexes in patients' sera, by an enzyme-linked immunosorbent assay (ELISA). Furthermore, to evaluate the expression of CK8, CK18 and CK19 in liver tissue, immunohistochemical stainings were performed. Significantly high levels of anti-CK8, anti-CK18 and anti-CK19 antibodies were demonstrated in patients with AIH compared with normal volunteers and patients with chronic active hepatitis C (CH-C). In addition, these antibodies were significantly decreased after steroid treatment. Levels of CK8:anti-CK8 and CK18:anti-CK18 immune complexes in sera of patients with AIH were significantly high compared with those of patients with CH-C and normal volunteers. Immunohistochemically, CK8 or CK18 were absent from some hepatocytes of AIH. CK19 was aberrantly expressed in periportal hepatocytes in patients with AIH, but not CH-C. This is the first study to quantify anti-CK8, anti-CK18, anti-CK19 antibodies and immune complexes in patients with AIH. The clinical significance of anti-CK antibodies and their immune complexes of AIH is also discussed.

Autoantibodies in alcoholic liver disease

Despite many decades of research, the reasons why only a relatively small proportion of individuals who consume excessive quantities of alcohol develop clinically significant liver disease remain unknown. The association with features of autoimmune diseases, including hypergammaglobulinaemia, circulating autoantibodies, inheritance of certain immunogenetic (HLA) markers and response to corticosteroid therapy in some patients has led to a persistent impression that altered immune regulation with a relative loss of self-tolerance underlies susceptibility to the development of the more severe forms of alcoholic liver disease (alcoholic hepatitis and/or cirrhosis). However, review of the data from the numerous studies that have been conducted over the past 30 years fails to reveal sufficiently convincing evidence that autoimmunity plays a primary role in alcohol-related liver damage. In particular, most of the wide range of circulating autoantibodies that have been reported in patients are found mainly at low titres, are not confined to those with severe liver injury, and are probably more likely to be a response to the hepatic insult than causally related to liver damage. Additionally, an association with various HLA phenotypes has not been confirmed by meta-analysis. Interpretation is complicated by evidence that alcohol may have direct effects on some components of the immune system but, if there is an immunogenetic basis for alcoholic liver disease, the present evidence suggests that this might be related more to cytokine gene polymorphisms than to a predisposition to autoimmunity per se.

Antibodies against acetaldehyde-modified protein epitopes in human alcoholics

Acetaldehyde, the primary metabolite of ethanol, binds covalently to proteins forming condensation products which have been recently shown to be immunogenic. To assess whether an antibody response against acetaldehyde-modified protein epitopes is associated with alcoholic liver disease, the serum immunoreactivity against proteins modified in vitro by acetaldehyde and against the corresponding unmodified proteins was measured by an enzyme-linked immunosorbent assay in 58 alcoholics with varying degrees of liver damage. Alcoholics showed significantly higher titers against protein-acetaldehyde conjugates than against the unmodified protein, independent of the nature of the carrier protein. The highest titers occurred in alcoholic hepatitis patients. Sera of patients with chronic hepatitis of nonalcoholic origin and of healthy controls also reacted with acetaldehyde conjugates, but their titers were significantly lower than those in alcoholic hepatitis patients. Our data support the idea that binding of acetaldehyde to proteins in humans generates antigenic determinants which trigger a corresponding immune response against such epitopes and suggest that this humoral immune response may be implicated in autoantibody formation and liver damage associated with excessive alcohol consumption.

The detection of smooth muscle antibodies reacting with intermediate filaments of desmin type

Some human smooth muscle antibodies (SMA) react with cytoskeletal intermediate filament (IMF) antigens. The smooth muscle tissue contains two types of IMF: vimentin and desmin filaments. In this study, SMA of anti-IMF type in 52 patients' sera have been classified into anti-vimentin filament and anti-desmin filament types according to their immunofluorescence staining patterns on rat testis. This classification is based on the fact that the arterial walls of testis contains both vimentin and desmin whereas the myoid cell layer surrounding the seminiferous tubuli contains only desmin. Four out of the 52 sera gave the anti-desmin staining pattern and 40 sera showed the anti-vimentin type of staining. Thirty-two sera were further classified by using cultured human rhabdomyosarcoma (RD) cells as targets. Nine sera reacted with the intermediate filaments of the RD cells. Among these were 3 out of the 4 sera that gave the anti-desmin filament staining pattern. The anti-desmin specificity of SMA was confirmed in 1 serum by the immunoblotting technique. These results indicate that while human anti-desmin filament antibodies exist, most human SMA of anti-IMF type react with vimentin filaments.