Increased C1q binding and arthritis in primary biliary cirrhosis

Autoantibodies against integral membrane proteins of the nuclear envelope in patients with primary biliary cirrhosis

BACKGROUND/AIMS

Autoantibodies against nuclear membrane proteins have been identified in patients with primary biliary cirrhosis (PBC). The aim of the present study was to determine the incidence of these autoantibodies in patients with PBC and examine their significance.

METHODS

An assay using recombinant polypeptides was designed to unequivocally detect autoantibodies against gp210 and the lamin B receptor, integral proteins of the nuclear membranes.

RESULTS

Autoantibodies against gp210 were detected in 15 of 159 patients with PBC and 0 of 46 controls. Autoantibodies against lamin B receptor were detected in 2 patients with PBC and 0 controls. The presence of these autoantibodies had a sensitivity of 11% and specificity of 100% for the diagnosis of PBC. Autoantibodies against gp210 were present in 4 of 19 (21%) patients with PBC who did not have detectable antimitochondrial antibodies. Patients with PBC and gp210 autoantibodies had a higher incidence of associated arthritis.

CONCLUSIONS

Autoantibodies against gp210 and the lamin B receptor are present in approximately 10% of patients with PBC. These autoantibodies are highly specific for the diagnosis of PBC and may be useful in diagnosing individuals without antimitochondrial antibodies and in identifying a subgroup of patients with an increased incidence of associated arthritis.

Endothelial cell damage in primary biliary cirrhosis: influence of cholestasis and immunological mechanisms

In a study looking for evidence of endothelial cell damage in primary biliary cirrhosis, serum from patients was found to be significantly more cytotoxic to cultured endothelial cells in vitro than normal control serum (P less than 0.001). Serum also contained higher levels of von Willebrand factor antigen (vWFAg, a specific product of the endothelium) than control serum (P less than 0.001). Cytotoxicity correlated with serum levels of vWFAg (P less than 0.05) and with serum bilirubin (P less than 0.05). No correlations were found between cytotoxicity and circulating immune complexes, C-reactive protein or CH50. The study was controlled by serum from patients with other liver diseases. In these samples vWFAg (P less than 0.003), and bilirubin levels (P less than 0.001) were also raised relative to normal controls. vWFAg levels again correlated with levels of bilirubin (P less than 0.05). Tissue culture experiments showed that purified bilirubin was cytotoxic to human umbilical vein endothelial cells and induced the release of vWFAg. The case report of a patient with obstructive jaundice again indicated that levels of bilirubin and vWFAg were related. These results suggest that endothelial cell damage occurs in both primary biliary cirrhosis and to a lesser extent in other liver diseases, and may be mediated by cholestasis, not by humoral immunological mechanisms.

Biochemical studies of immune complexes. I. Isolation of circulating immune complexes using a bifunctional exclusion chromatography matrix

A simple and rapid method of isolating immune complexes from serum is described. The method utilizes the binding properties of a bifunctional chromatography matrix consisting of diethylaminoethyl and Cibacron blue F3GA functional groups linked to agarose beads. This column matrix binds all normal serum proteins except IgG and transferrin, excluding these proteins, and permitting them to be collected in the wash-through, void volume. Immune complexes prepared in vitro with human serum albumin were rapidly isolated from starting serum by this method. This method may have general application for the purification of immune complexes from serum in pathological conditions and should foster subsequent biochemical and immunological studies, including identification and characterization of immune complex antigens.

Circulating immune complexes in primary biliary cirrhosis: interactions with lymphoid cells

To evaluate the interactions between circulating immune complexes (CIC) and lymphoid cells in primary biliary cirrhosis (PBC), we determined (1) whether antibodies to lymphocytes in PBC serum, independent of CIC, could account for binding in the Raji cell assay for CIC and (2) whether CIC or other humoral factors in PBC serum could interact with lymphoid cells to alter their function. We found that three quarters of CIC positive PBC sera bound specifically to Raji cells via complement receptors, while only one quarter had antibodies to lymphoid cells or Raji cells devoid of complement receptors. We also demonstrated factors which inhibited cell-mediated cytotoxicity and suppressor cell activity in PBC sera; however, we found no correlation between the level and presence of CIC or of lymphocyte antibodies and the level or presence of these serum inhibitory factors. Thus, although the detection of CIC in PBC is not artifactual, the contribution of CIC and other serum factors to the other immunological aberrations in PBC remains to be elucidated.