Methods Serum of 184 Belgian SSc patients with a known SSc-antibody profile, was analyzed for PBC-Ab (antimitochondrial antibodies [AMA], anti-Gp210, anti-Sp100 and anti-PML) using indirect immunofluorescence (IIF) analysis on human epithelioma-2000 (HEp-2000) cells (ANA-IIF, Immunoconcepts) and liver-kidney-stomach tissue sections (IIF-LKS) (Menarini), and a line immunoblot (LB) (EuroImmun).
To further define specific classical human leukocyte antigen (HLA) alleles or amino acids associated with the sp100 autoantibody, we imputed 922 PBC cases (211 anti-sp100-positive versus 711 negative cases) using a Han Chinese MHC reference database.
The diagnostic value of antinuclear antibodies (ANAs) including anti-gp210 and anti-sp100 for primary biliary cholangitis/cirrhosis (PBC) has been widely reported.
Regarding primary biliary cholangitis (PBC), two of eight patients were positive for MIT3 autoantibodies, both confirmed by immunofluorescence, and one patient was positive for PBC-specific antinuclear antibodies, sp100.
In conclusion, our results show that SP140L is phylogenetically recent member of SP100 proteins and acts as an autoantigen in primary biliary cirrhosis patients.
These results provide a platform to dissect the mechanisms of gp210 and sp100 autoantibody production in dnTGF-βRII mice as well as to study the possible role of ANA in the pathophysiology of PBC.
By using immobilized synthetic peptides and various sp100-positive PBC patient sera the corresponding epitopes could be shown to be centered around epitope cores of six amino acids (SNSKVE, antigenic region 1) and nine amino acids (EPLEVFISA, antigenic region 2) respectively.
These data imply that NDP52 forms homodimers but no heterodimers with Sp100 and PML, lacks autoantigenicity in PBC, localizes mainly in the cytoplasm, and is associated with the nucleus, but not with NDs.
Current knowledge clearly indicates that determination of anti-Sp100 and anti-PML autoantibodies substantially improves diagnosis of PBC as these autoantibodies are highly specific for this disease even when autoantibodies against mitochondrial antigens, a hallmark of most PBC patients, are not found.
We show that autoantibodies against both PML and Sp100 are usually associated in sera with multiple nuclear dot anti-nuclear antibodies and demonstrate that PML is an autoantigen, not only in PBC, but also in other autoimmune diseases.