IgA deposition in alcoholic liver disease

Immunoglobulin A and liver diseases

Immunoglobulin A (IgA) is a major immunoglobulin isotype in the gut and plays a role in maintenance of gut homeostasis. Secretory IgA (SIgA) has multiple functions in the gut, such as to regulate microbiota composition, to protect intestinal epithelium from pathogenic microorganisms, and to help for immune-system development. The liver is the front-line organ that receives gut-derived products through the portal vein, implying that the liver could be severely affected by a disrupted intestinal homeostasis. Indeed, some liver diseases like alcoholic liver disease are associated with an altered composition of gut microbiota and increased blood endotoxin levels. Therefore, deficiency of SIgA function appears as a significant factor for the pathogenesis of liver diseases associated with altered gut microbiome. In this review, we describe SIgA functions on the gut microbiome and discuss the role of IgA for liver diseases, especially alcoholic liver disease and non-alcoholic fatty liver disease/non-alcoholic steatohepatitis.

[Contribution of hepatic immunoglobulin A deposits to the diagnosis of alcoholic hepatopathy]

BACKGROUND

Alcoholic hepatic disease is a severe and frequent disease and its diagnosis is not always an easy task.

AIM

To assess the contribution of immunoglobulin A (IgA) in the hepatic sinusoids for diagnosis of alcoholic hepatopathy.

PATIENTS AND METHODS

The presence of IgA was studied through direct immunofluorescence in 59 patients submitted to hepatic needle biopsy, indicated by clinical or in vitro changes suggestive of chronic hepatopathy.

RESULTS

A significant deposition of IgA was found in alcoholic patients as compared to non-alcoholic patients, with 76% sensitivity (95% CI: 54.5-89.8) and 73.5% specificity (95% CI: 55.3-86.5). In individuals who present only alcohol as the etiological agent of hepatopathy, compared with the subgroup of B or C virus carriers, the results were even more significant, with 85.7% sensitivity (95% CI: 56.2-97.5) and 89.5% specificity (95% CI: 65.5-98.2).

CONCLUSION

The deposition of IgA in the hepatic sinusoids present sensitivity and specificity for the diagnosis of an alcohol-induced hepatic lesion. This resource can be particularly useful when conventional histology can not be define a specific cause for the change found.

IgA deposition in the skin of patients with alcoholic liver disease

In patients with alcoholic liver disease, IgA deposits are often found in the liver, kidneys and skin. The present study was undertaken to determine the specificity, sensitivity and characteristics of IgA deposition in the skin of a group of alcoholic patients with or without overt liver disease, and compare these with findings in non-alcoholic cirrhotics. Twenty-six out of 28 patients with alcoholic cirrhosis had IgA deposition in the skin. In contrast, only 6 out of 11 patients who were alcoholic without any clinical liver disease and 3 out of 13 patients with non-alcoholic cirrhosis of the liver had IgA deposition. In the control group, only 1 out of 52 patients with various dermatoses (excluding IgA dermatoses) had this IgA deposition. Unlike other IgA dermatoses, such as Henoch-Schoenlein purpura or dermatitis herpetiformis, IgA deposition in alcoholic liver disease is characterized by its presence in the basement membrane of the eccrine secretory coils. This particular pattern of IgA deposition can be helpful in the diagnosis of alcoholic liver disease or alcoholism since the specificity is 100% with a sensitivity of 75%.

Cell-mediated hepatic injury in alcoholic liver disease. Veterans Affairs Cooperative Study Group 275

BACKGROUND

The mechanism responsible for the initiation and perpetuation of alcoholic liver disease (ALD) remains poorly understood. This investigation attempted to elucidate the role of cell-mediated immune phenomena in the pathogenesis of ethanol-induced liver injury.

METHODS

Frozen liver biopsy specimens from 144 patients with moderate to severe ALD were examined by the avidin-biotin immunoperoxidase technique for the expression of antigenic markers of T and B lymphocytes, natural killer cells, and class I and II MHC molecules in the tissue.

RESULTS

Expression of CD3 by lymphocytes correlated significantly with regenerating nodules, intralobular inflammation, central sclerosis, and abnormalities of Kupffer cells. B cells were rarely present, and natural killer cells were absent. CD3+ lymphocytes expressed either CD4 or CD8 surface molecules. Enhanced class I MHC expression correlated significantly with portal inflammation, limiting plate erosion, vascular abnormalities, and hemosiderosis. Expression of class II MHC molecules correlated significantly with necrosis, bile stasis, and Mallory bodies.

CONCLUSIONS

The distribution and persistence of CD4+ and CD8+ cells in actively advancing ALD, the enhanced MHC expression on hepatocytes, and their relationship to alcoholic hyalin and necrosis lend support to the hypothesis that a cytotoxic T lymphocyte-hepatocyte interaction plays a role, perhaps via lymphokine production, in the genesis or perpetuation of ALD.

Alcoholic liver disease: pathologic, pathogenetic and clinical aspects

Alcoholic liver disease includes steatosis, alcoholic hepatitis and cirrhosis. Other liver diseases of genetic origin, but with a curious association with alcohol intake, are hemochromatosis and porphyria cutanea tarda. The attribution of chronic hepatitis to alcohol intake remains speculative, and the association may reflect hepatitis C infection. Hepatic injury attributed to alcohol includes the changes reported in the fetal alcohol syndrome. Steatosis, the characteristic consequence of excess alcohol intake, is usually macrovesicular and rarely microvesicular. Acute intrahepatic cholestasis, which in rare instances accompanies steatosis, must be distinguished from other causes of intrahepatic cholestasis (e.g., drug-induced) and from mechanical obstruction of the intrahepatic bile ducts (e.g., pancreatitis, choledocholithiasis) before being accepted. Alcoholic hepatitis (steatonecrosis) is characterized by a constellation of lesions: steatosis, Mallory bodies (with or without a neutrophilic inflammatory response), megamitochondria, occlusive lesions of terminal hepatic venules, and a lattice-like pattern of pericellular fibrosis. All these lesions mainly affect zone 3 of the hepatic acinus. Other changes, observed at the ultrastructural level, are of importance in progression of the disease. They include widespread cytoplasmic shedding, and capillarization and defenestration of sinusoids. Progressive fibrosis complicating alcoholic hepatitis eventually leads to cirrhosis that is typically micronodular but can evolve to a mixed or macronodular pattern. Hepatocellular carcinoma occurs in 5 to 15% of patients with alcoholic liver disease. The clinical syndrome of alcoholic liver disease is the result of three factors--parenchymal insufficiency, portal hypertension and the clinical consequences of extrahepatic damage produced by alcohol. At the several phases of the life history of alcoholic liver disease, the individual factors play a different role. The clinical manifestations of alcoholic steatosis are mainly extrahepatic in origin. Those of alcoholic hepatitis reflect mainly parenchymal insufficiency and those of cirrhosis are mainly those of portal hypertension. Alcoholic liver injury appears to be generated by the effects of ethanol metabolism and the toxic effects of acetaldehyde, perhaps the immune responses to alcohol- or acetaldehyde-altered proteins, and questionably enhanced by viral hepatitis. Alcoholic hepatitis may be mimicked histologically, and to a varying degree clinically, by a number of conditions (obesity, diabetes, several drug-induced injuries, jejunoileal bypass, and related "shortcircuiting" of the bowel). Perhaps the most important facet of the hepatotoxicity of alcohol is its enhancement of the effects of a number of other hepatotoxic agents, among which acetaminophen is the prime example.

The liver and IgA: immunological, cell biological and clinical implications

Secretory immunoglobulin A is the characteristic and predominant immunoglobulin of the mucosal immune system; it participates in immunological protection at the level of mucous membrane surfaces. During the past 10 to 15 years, a great deal of experimental and clinical evidence has shown that the liver is very much involved in the sIgA system. In certain animals (rats, mice, rabbits), polymeric forms of IgA are efficiently cleared by the liver and transported into bile by a receptor-mediated vesicular pathway across hepatocytes. Taking advantage of this easily accessible pathway, investigators have defined many of the events in the external secretion of pIgA, including details about the synthesis and secretion of its receptor, secretory component. In the rat hepatocyte, secretory component is synthesized as a transmembrane glycoprotein and is expressed preferentially on the sinusoidal plasma membrane; circulating pIgA that binds to secretory component is internalized into endocytic vesicles and transported across the hepatocyte to the bile canalicular membrane, where the pIgA is released into bile as a soluble complex with a portion of the secretory component, the complex being secretory IgA. In some other animals (dog, guinea pig, sheep) as well as man, biliary epithelial cells, not hepatocytes, express secretory component and perform the transcytosis and secretion of pIgA into bile. In those species, much of the pIgA that reaches bile is synthesized locally in plasma cells that populate the biliary tree; this design is analogous to the release of sIgA into various mucosae in the body. The major biological functions ascribed to the secretion of IgA into bile are enhancement of immunological defense of the biliary and upper intestinal tracts and the clearance of harmful antigens from the circulation as IgA-antigen complexes. However, the importance of biliary IgA antibodies is largely unclarified, and man lacks the capacity for effective clearance of IgA-antigen complexes via the secretory component-mediated transhepatocellular pathway; whether this deficit contributes to the propensity for man to develop IgA immune complex diseases should be clarified. Among liver diseases, alcoholic disease is most closely linked to alterations in IgA metabolism. This association is manifested principally by the deposition of IgA along the sinusoids in the livers of the majority of alcoholics and in the renal mesangium of many.(ABSTRACT TRUNCATED AT 400 WORDS)

Does a linear pattern of sinusoidal IgA deposition distinguish between alcoholic and diabetic liver disease?

IgA deposition in hepatic sinusoids was demonstrated in liver biopsies from 26 patients with alcohol- or diabetes-related fatty liver and fatty liver hepatitis, and from 13 patients with normal liver or chronic active hepatitis. The pattern and extent of IgA deposition were similar in alcoholic and diabetic patients, a linear, continuous pattern being the most common. Staining for IgA cannot therefore be used to evaluate aetiology of fatty liver hepatitis in these two groups of patients.

Immunoglobulin A in the diagnosis of alcoholic liver disease

The diagnostic relevance of the serum immunoglobulin A (IgA) concentration and liver deposition of IgA for chronic excessive alcohol consumption was evaluated in 164 patients with biochemical liver abnormalities. A relationship was demonstrated between the amount of daily alcohol consumption and the two IgA parameters and serum gamma-glutamyl transpeptidase. A continuous pattern of IgA deposition along hepatic sinusoids proved to be the best diagnostic feature, combining a specificity of 0.91 with a sensitivity of 0.75. Although serum IgA has a specificity of 0.78, its diagnostic value is restricted by a sensitivity of 0.50, making it not superior to serum gamma-glutamyl transpeptidase. Furthermore, serum IgA proved to be related to liver histopathology. High levels of serum IgA are found in hepatitis and cirrhosis, without significant differences between alcoholic and nonalcoholic patients. However, in the case of mild histopathologic changes in the liver, such as steatosis and fibrosis, significantly higher serum IgA concentrations are found in alcoholic than in nonalcoholic liver disease.