GASTROENTEROLOGY 1992;103:1889-1887 Immunoglobulin A Antibody to a 2OO- Kilodalton Cytosolic Acetaldehyde Adduct in Alcoholic Hepatitis JOHN KOSKINAS, J. GERALD KENNA, GEORGE L. BIRD, GRAEME J. M. ALEXANDER, and ROGER WILLIAMS Institute of Liver Studies, King’s College School of Medicine and Dentistry; and Department of Pharmacology and Toxicology, St. Mary’s Hospital Medical School (Imperial College], London, England Considerable clinical and experimental evidence points to the importance of immune responses in the development of alcoholic liver disease. In the present study it was investigated whether circulat- ing antibodies from patients with alcoholic liver disease recognize acetaldehyde-liver protein ad- ducts. Cytosolic and microsomal fractions from livers of Wistar rats or from normal human liver were incubated with acetaldehyde (0.5-2.5 mmol/ L) and/or cyanoborohydride (100 mmol/L) then an- alysed by immunoblotting. Cytosolic fractions that had been incubated with acetaldehyde and cyano- borohydride expressed a 200-kilodalton protein an- tigen not present in untreated fractions or fractions incubated with acetaldehyde or cyanoborohydride alone. The 200-kilodalton antigen was recognized by immunoglobulin (1g)A antibodies in a large pro- portion of sera from patients with alcoholic hepati- tis (70%, n = 23), but in significantly smaller pro- portions of sera from patients with alcoholic cirrhosis without hepatitis (30%, n = 10; P c 0.05), heavy drinkers without overt liver disease (2O%, n = 10; P < 0.02), patients with nonalcoholic liver disease (357’0, n = 17; P < O.O5), or normal control subjects consuming moderate quantities of alcohol (25%, n = 20; P < 0.005). These results indicate that IgA antibodies to a 200-kilodalton acetaldehyde- protein adduct are present in a large proportion of patients with alcoholic liver disease and in a signifi- cantly smaller proportion of other individuals. H umoral immunity-may play an important role in the pathogenesis of alcoholic liver disease.lW3 Antibodies to antigenic determinants in Mallory bod- ies,4*5 liver specific proteins,‘p7 and liver membrane antigen,‘-” which might have specific roles with re- spect to perpetuation and/or exacerbation of eth- anol-induced liver damage, have all been described. Circulating antibodies to hepatocytes from rabbits pretreated with alcohol but not to untreated cells have also been reported in alcoholic liver disease”-‘3 and could be involved at an earlier stage of the hepa- tocyte damage. The target antigen of these latter anti- bodies is believed to be one or more normal cellular constituents that have been modified by alcohol or acetaldehyde. In alcoholic subjects, tissue and blood levels of ac- etaldehyde are highI as a result of an enhanced rate of metabolism of ethanol to acetaldehyde15 and re- duced activity of hepatic acetaldehyde dehydroge- nase.16 Acetaldehyde is notable for its ability to bind to organellar proteins, leading to the formation of both stable and unstable protein adducts.‘7-23 Exper- iments performed using artificial acetaldehyde pro- tein conjugates have shown that covalently bound acetaldehyde-protein adducts are formed at concen- trations of acetaldehyde comparable to those found in the blood of alcoholics and that such adducts are strongly immunogenic. 24*25 Thus antibodies reactive with acetaldehyde-protein adducts have been shown in mice and rats fed alcohol long-term.2”r27 In addition, high titers of antibodies to synthetic acetal- dehyde-hemoglobin or acetaldehyde-albumin ad- ducts have been reported in patients with alcoholic liver disease, whereas in healthy controls the titers of such antibodies are 10w.~‘-~~ In principle, a wide range of different acetalde- hyde-protein adducts might be produced in tissues of ethanol-exposed individuals, some or all of which might have the potential to elicit antibody responses. Indeed, the formation of 37- and %kilodalton acetal- dehyde-protein adducts within the liver of rats fed alcohol long-term has been reported.32-34 Thus it is important to determine the detailed antigenic speci- ficities of the patients ’ “antiacetaldehyde” antibod- ies and to determine whether the antibodies recog- nize discrete acetaldehyde-tissue protein adducts. Acetaldehyde-modified hepatic proteins are of par- ticular interest because they may be targets of hepa- 0 1992 by the American Gastroenterological Association 0016-5085/92/$3.00