Anti-ribosomal P protein: a novel antibody in autoimmune hepatitis

Background Autoantibodies to ribosomal P proteins (anti-rib P) are specific serological markers for systemic lupus erythematosus (SLE) and are associated with liver involvement in this disease. The similarity in autoimmune background between autoimmune hepatitis (AIH) and SLE-associated hepatitis raises the possibility that anti-rib P antibodies might also have relevance in AIH. Aims To evaluate the frequency and clinical significance of anti-rib P antibodies in a large AIH cohort. Methods Sera obtained at diagnosis of 96 AIH patients and of 82 healthy controls were tested for IgG anti-ribosomal P protein by ELISA. All of the sera were also screened for other lupus-specific autoantibodies, three patients with the presence of anti-dsDNA (n=1) and anti-Sm (n=2) were excluded. Results Moderate to high titres (>40U) of anti-rib P antibody were found in 9.7% (9/93) of the AIH patients and none of the controls (P=0.003). At presentation, AIH patients with and without anti-rib P antibodies had similar demographic/clinical features, including the frequency of cirrhosis (44.4 vs. 28.5%, P=0.44), hepatic laboratorial findings (0.05). Importantly, at the final observation (follow-up period 10.2 +/- 4.9years), the AIH patients with anti-rib P had a significantly higher frequency of cirrhosis compared with the negative group (100 vs. 60%, P=0.04). Conclusion The novel demonstration of anti-rib P in AIH patients without clinical or laboratory evidence of SLE suggests a common underlying mechanism targeting the liver in these two diseases. In addition, this antibody appears to predict the patients with worse AIH prognoses.