Humoral autoimmune response heterogeneity in the spectrum of primary biliary cirrhosis

Abstract

Objective: To compare autoantibody features in patients with primary biliary cirrhosis (PBC) and individuals presenting antimitochondria antibodies (AMAs) but no clinical or biochemical evidence of disease.

Methods: A total of 212 AMA-positive serum samples were classified into four groups: PBC (definite PBC, n = 93); PBC/autoimmune disease (AID; PBC plus other AID, n = 37); biochemically normal (BN) individuals (n = 61); and BN/AID (BN plus other AID, n = 21). Samples were tested by indirect immunofluorescence (IIF) on rat kidney (IIF-AMA) and ELISA [antibodies to pyruvate dehydrogenase E2-complex (PDC-E2), gp-210, Sp-100, and CENP-A/B]. AMA isotype was determined by IIF-AMA. Affinity of anti-PDC-E2 IgG was determined by 8 M urea-modified ELISA.

Results: High-titer IIF-AMA was more frequent in PBC and PBC/AID (57 and 70 %) than in BN and BN/AID samples (23 and 19 %) (p < 0.001). Triple isotype IIF-AMA (IgA/IgM/IgG) was more frequent in PBC and PBC/AID samples (35 and 43 %) than in BN sample (18 %; p = 0.008; p = 0.013, respectively). Anti-PDC-E2 levels were higher in PBC (mean 3.82; 95 % CI 3.36-4.29) and PBC/AID samples (3.89; 3.15-4.63) than in BN (2.43; 1.92-2.94) and BN/AID samples (2.52; 1.54-3.50) (p < 0.001). Anti-PDC-E2 avidity was higher in PBC (mean 64.5 %; 95 % CI 57.5-71.5 %) and PBC/AID samples (66.1 %; 54.4-77.8 %) than in BN samples (39.2 %; 30.9-37.5 %) (p < 0.001). PBC and PBC/AID recognized more cell domains (mitochondria, nuclear envelope, PML/sp-100 bodies, centromere) than BN (p = 0.008) and BN/AID samples (p = 0.002). Three variables were independently associated with established PBC: high-avidity anti-PDC-E2 (OR 4.121; 95 % CI 2.118-8.019); high-titer IIF-AMA (OR 4.890; 2.319-10.314); antibodies to three or more antigenic cell domains (OR 9.414; 1.924-46.060).

Conclusion: The autoantibody profile was quantitatively and qualitatively more robust in definite PBC as compared with AMA-positive biochemically normal individuals.

Keywords: Antibody affinity; Autoantibodies; Autoimmune liver diseases; Autoimmunity.

Fig. 1

Algorithm for selection of samples according to the identification of the peculiar cytoplasm mitochondria-like pattern in the antinuclear antibody (ANA) indirect immunofluorescence (IIF) assay on HEp-2 cells assay

Fig. 2

Distribution of samples according to a indirect immunofluorescence (IIF) on rat kidney (IIF-AMA) titer (p < 0.001), b number of IIF-AMA isotypes (p = 0.005), c number of antigenic cellular domains targeted (p = 0.005). BN, AMA-reactive individuals with normal levels of alkaline phosphatase; BN/AID, same as BN but with any associated extrahepatic autoimmune disease; PBC, definite primary biliary cirrhosis; PBC/AID, definite primary biliary cirrhosis and any associated extrahepatic autoimmune disease

Fig. 3

Distribution of samples according to a titer concentration (IU/mL) of anti-PDC-E2 IgG (p < 0.001) and b avidity of anti-PDC-E2 IgG (p < 0.001). Receiver operating curve analysis comparing PBC and PBC/AID samples versus BN and BN/AID samples according to c titer concentration (IU/mL) of anti-E2-PDC IgG [AUC = 0.679 (95 % CI 0.606–0.751)] and d avidity of anti-E2-PDC IgG [AUC = 0.704 (95 % CI 0.633–0.755)]. BN, AMA-reactive asymptomatic individuals with normal levels of alkaline phosphatase; BN/AID, same as BN but with any associated extrahepatic autoimmune disease; PBC, definite primary biliary cirrhosis; PBC/AID, definite primary biliary cirrhosis and any associated extrahepatic autoimmune disease

Fig. 4

Distribution of samples according to results of ELISA tests. a Anti-CENP-A/B antibody serum levels presented higher values in PBC/AID samples as compared with PBC (p = 0.006), BN (p < 0.001), and BN/AID samples (p = 0.030). b Anti-gp210 antibody serum levels were higher in PBC and PBC/AID groups as compared with that in BN and BN/AID groups (p = 0.0032). c Anti-Sp-100 antibody serum levels showed no difference among the groups of samples (p = 0.808). BN, AMA-reactive asymptomatic individuals with normal levels of alkaline phosphatase; BN/AID, same as BN but with any associated extrahepatic autoimmune disease; PBC, definite primary biliary cirrhosis; PBC/AID, definite primary biliary cirrhosis and any associated extrahepatic autoimmune disease