The aim of our study was to evaluate antibodies against 'specific liver' antigens in selected sera from patients with positive 'AMA like' and unidentified (UD) Hep2 cytoplasmic immunofluorescence (ctp IIF).
Sera of 75 inpatients and outpatients from the Department of Rheumatology, Ljubljana met the inclusion criteria: 36 with AMA-like and 39 with UD pattern. All sera were also negative for anti-M2 and/or antibodies against pyruvat dehydrogenase complex as well as negative to other defined ctp IIF patterns according to European Consensus Finding Study: lysosomal-like, Golgi-like, vimentin-like and actin-like. The majority of patients fulfilled the criteria for connective tissue diseases and rheumatoid arthritis.
Antibodies against intracellular antigens were screened by IIF on HEp2 cells (Immunoconcepts, Sacramento, CA, USA). Antibodies against LKM1, SLA, LC1 and Sp100 were performed by line immunoassay (Imtec, Berlin, Germany).
There was no difference in AMA-like and UD ctp IIF concerning antibodies against 'specific liver' antigens. A surprisingly high prevalence of positive anti-LKM1 was found in sera regardless of the IIF pattern (Table 1).
Table 1. Antibodies against 'liver specific' antigens in sera with AMA-like and UD ctp IIF
Anti-LKM1 has been considered as one of the markers for autoimmune hepatitis type II characterised by fulminant onset and high inflammatory activity according to Imtec data. None of our patients with positive anti-LKM1 had any serious hepatic involvement, therefore they had not been histopathologically evaluated. Only few of them exhibited minor deviations in liver enzymes (less than 1 × upper normal limit). There was slightly lower prevalence of connective tissue disease patients found among UD ctp IIF (Table 2).
Table 2. Antibodies against 'liver specific' antigens in sera with AMA-like and UD ctp IIF
An UD ctp IIF pattern is a frequent laboratory finding but it seems not to be of much help to rheumatologists. A search for antibodies against 'specific liver' antigens seems not to be justified for delineation of hepatic involvement in patients with rheumatic diseases. According to the literature in patients with autoimmune hepatitis the meaning of these antibodies is different.