Alcoholic and, to a lesser extent, nonalcoholic patients with liver di
sease have serum antibodies to acetaldehyde-protein adducts produced i
n vitro. These antibodies presumably reflect the presence of adducts i
n the liver, but the protein that triggers this immune response has no
t been identified. To study this, we measured the reactivity of cytoso
lic proteins to rabbit IgG developed against a P-450 2E1-acetaldehyde
adduct, isolated from alcohol-fed rats, that recognizes acetaldehyde-m
odified epitopes in proteins. Adducts were determined on Western blots
by scanning densitometry of antibody-linked alkaline phosphatase acti
vity in 4 normal livers and in needle biopsy specimens from subjects w
ith liver disease, 17 alcoholic and 14 nonalcoholic. In all livers, ex
cept for a normal one, we found a reactive protein of at least 200 kD,
similar to the collagen-acetaldehyde adduct we reported to be markedl
y increased in rats with experimentally induced cirrhosis. The immunos
taining intensity in the alcoholic patients with liver disease was eig
htfold (p < 0.01) and that in nonalcoholic patients with liver disease
was fourfold, greater (p < 0.02) than the weak staining in normal liv
ers; it correlated with the degree of inflammation and serum AST or ga
mma-glutamyl transpeptidase activities. The adduct was reproduced on i
ncubation of normal cytosolic proteins with 2.5 mmol/L acetaldehyde, w
hereas higher concentrations yielded many additional adducts; the addu
ct also reacted with IgG antibody to rat collagen type I and disappear
ed after digestion with collagenase, suggesting that the target protei
n is a form of collagen. The association of this collagen-acetaldehyde
adduct with parameters of liver disease activity suggests that the ad
duct reflects the liver injury and may even contribute to its developm
ent, both in alcoholic and in nonalcoholic subjects.