ab22303

Expression of Ro/SS-A and La/SS-B determined by immunohistochemistry in healthy, inflamed and autoimmune diseased human tissues: a generalized phenomenon

J.M. van Woerkom, J.G.N. Geertzema¹, P.G.J. Nikkels¹, A.A. Kruize, R.J.T. Smeenk², T.M. Vroom¹

Department of Rheumatology & Clinical Immunology and ¹Department of Pathology, University Medical Center Utrecht, Utrecht; ²Department of Autoimmune Diseases, Sanquin Blood Supply Foundation, Central Laboratory, Amsterdam, The Netherlands.

ABSTRACT
Objective
Autoantibodies to the ribonucleoproteins Ro/SS-A and La/SS-B are found in autoimmune diseases such as primary Sjögren's syndrome (pSS), systemic lupus erythematousus and rheumatoid arthritis. Increased and aberrant expression of Ro/SS-A and La/SS- B in target organs, which have been reported in the recent literature, might contribute to their antigenicity. However, data on the expression of Ro/SS-A and La/SS-B in other inflammatory conditions are scarce.

Materials and methods
Using monoclonal antibodies against Ro/SS-A and La/SS-B, we studied the expression of these antigens in paraffin-embedded healthy tissue, aspecific inflamed tissue, the neonatal and adult cardiac conduction systems and labial salivary gland tissues of patients suspected of having pSS.

Results
In healthy tissues, the nuclei expressed both Ro/SS-A and La/SS-B. This expression was stronger in inflamed tissues. Nucleoli were negative and cytoplasmic expression was weaker than nuclear expression. No increased or aberrant expression of Ro/SS-A or La/SS-B was observed in either neonatal or adult atrioventicular nodes and bundle branches. More pSS patients showed high La/SS-B immunoreactivity levels in their labial salivary gland ductal cell nuclei than non-Sjögren's syndrome sicca patients.

Conclusions
Ro/SS-A and La/SS-B expression is a generalized cell biological phenomenon and may be upregulated by increased cell activation both in aspecific and autoimmune-mediated inflammation. In pSS the high expression of La/SS-B in labial salivary gland ductal cell nuclei might contribute to the local immune response.

Key words
Ro/SS-A, La/SS-B, Sjögren's syndrome, immunohistochemistry, congenital heart block.

Department of Rheumatology & Clinical Immunology, University Medical Center Utrecht, PO Box 85500, 3508 GA Utrecht, The Netherlands.
E-mail: j.vanwoerkom@azu.nl