ab2002

Interleukin-13 in autoimmune rheumatic diseases: Relationship with the autoantibody profile

A. Spadaro, T. Rinaldi, V. Riccieri, E. Taccari,G. Valesini

Department of Medical Therapy - Rheumatology Unit. University of Rome "La Sapienza", Italy.

ABSTRACT
Objective
Several cytokines play a role in the production of autoantibodies such as RF and ANA by B-lymphocytes; the role of IL-13 in this process has not been previously studied. We investigated the relationship between the serum concentration of this cytokine and circulating autoantibodies.

Methods
IL-13 serum levels, as well as RF and ANA, were evaluated in 282 patients with autoimmune rheumatic diseases including RA (n=84), SLE (n=114), SS (n=52) and Scl (n=32).

Results
Serum levels of IL-13 (pg/ml) were significantly higher in patients with RA (p < 0.00003), SLE (p < 0.03), SS (p < 0.0007), or Scl (p < 0.025) compared to controls. IL-13 serum levels correlated with those of RF in RA (p < 0.00001), SLE (p < 0.003) and Scl (p < 0.03). IL-13 levels were higher in RA (p<0.0003), SLE (p<0.005) and Scl (p<0.05) patients with RF than in patients without RF. SS patients with anti-SSA/Ro antibodies had significantly higher IL-13 levels than SS patients without this autoantibody (p < 0.04). No statistically significant correlation was found between IL-13 levels and any other antinuclear autoantibody, total immunoglobulin levels or the main clinical features of each disease.

Conclusion
The evidence of higher IL-13 levels in our RA, SLE, SS and Scl patients confirms that this cytokine is involved in the pathogenesis of autoimmune rheumatic diseases. The relationship of this cytokine with RF in RA, SLE and Scl, as well as with antiSSA/ Ro antibody in SS, strengthens the hypothesis that it plays a role in autoantibody production. However, the different autoantibody synthesis by B-cells recognises different pathways depending on the underlying autoimmune disease.

Key words
Interleukin-13, rheumatoid factor, antinuclear antibodies, autoimmune rheumatic diseases.

Please address correspondence and reprint requests to: Antonio Spadaro, Dipartimento di Terapia Medica, Divisione di Reumatologia, Università di Roma "La Sapienza", Azienda Policlinico Umberto I, Viale del Policlinico 155, 00161 Roma, Italy.