Low molecular weight IgM in primary biliary cirrhosis

Complement system is not activated in primary biliary cirrhosis

There is controversial evidence suggesting that the classical pathway of complement system is chronically activated in primary biliary cirrhosis (PBC) and that complement activation may be important in development of bile duct injury. We have reevaluated this issue by measuring by-products of complement activation such as C4a, C3a, Bb, and terminal complement complexes (SC5b-9) in plasma of 44 PBC patients with sensitive methods not previously used to detect complement activation in this disease. Age-matched healthy women and patients with chronic hepatitis of different etiology were studied as controls. We found that PBC patients have normal C4a concentrations. This finding argues strongly against chronic classical pathway activation. Although a minor increase of C3a levels was observed in a minority of PBC patients, the C3a/C3 ratio, an index used to evaluate the extent of native protein conversion, was remarkably similar in all groups. Potentially lytic terminal complement complexes were not increased. PBC patients had normal Bb plasma levels, indicating that the alternative pathway is also not activated. C3 concentration was higher in PBC patients than in healthy subjects and in chronic hepatitis patients, particularly in the early stages of the disease. C3 and C4 concentrations became lower in PBC and chronic hepatitis with the progression of the disease. The increase of C3 concentration in PBC does not reflect liver inflammation, since serum levels of C-reactive protein are normal. We found high serum C3 levels in patients with rare chronic cholestatic syndromes without superimposed infections and observed that serum C3 levels paralleled those of bilirubin in a patient with benign recurrent intrahepatic cholestasis. In conclusion, our data indicate that complement is not activated in PBC and that the increase of serum C3 levels is related to cholestasis.

Primary biliary cirrhosis is associated with specific changes in liver IgG-bearing cell subpopulations

BACKGROUND/AIMS

The density of total IgG-bearing cells and the distribution of their subclasses were studied in the liver of patients with primary biliary cirrhosis.

METHODS

Immunohistochemistry and computerized image analysis were used to compare liver specimens from 18 patients with primary biliary cirrhosis and 28 with chronic hepatitis of different etiology.

RESULTS

The density of total IgG-bearing cells was similar in the two groups. However, in patients with primary biliary cirrhosis the proportion of IgG3-positive cells was significantly higher than in patients with chronic hepatitis (53 +/- 7% vs. 7.5 +/- 2.4%) (p < 10(-8)). Conversely, IgG1-positive cells were significantly less prevalent in patients with primary biliary cirrhosis than in chronic hepatitis patients (27 +/- 6.9% vs. 68 +/- 7.2%, p < 10(-8)). Stratification of patients with primary biliary cirrhosis according to histology did not show any difference in the distribution of IgG subclasses associated with the progression of disease.

CONCLUSION

These data suggest a pathogenetic role of local IgG3-bearing cells in primary biliary cirrhosis.

An enhanced chemiluminescence detection system combined with a modified immunoblot technique for the detection of low molecular weight IgM in sera from healthy adults and neonates

An enhanced chemiluminescence detection system combined with a modified immunoblot technique is described for the detection of low molecular weight IgM (LMW IgM) in human sera and cell culture supernatants at levels down to 2 pg/ml. This detection system is reliable, specific and more sensitive than the previously described chromogenic detection system. Importantly, this method has, for the first time, revealed LMW IgM in the sera from all 34 healthy adults and 26 neonatal cord bloods tested. A significant linear correlation was observed between the LMW IgM and the total circulating IgM in both the healthy adult sera (r = 0.88, p less than 0.001) and cord blood sera (r = 0.98, p less than 0.001).