Longitudinal study of interleukin-10, tumor necrosis factor-alpha, anti-U1-snRNP antibody levels and disease activity in patients with mixed connective tissue disease

Objective. To investigate the levels and relationship between IL-10, TNF-al pha, anti-UlsnRNP antibodies and disease activity in longitudinally collect ed serum samples from patients with mixed connective tissue disease (MCTD). Methods. Six patients followed for 17-138 months were investigated with ELI SA for estimation of cytokine levels and antibodies to the different epitop es of the UlsnRNP. Disease activity was assessed by systemic lupus activity measure (SLAM). Results. IL-10 and TNF-alpha levels fluctuated with time in at least half o f the patients. Three patients had increased IL-10 levels and two had incre ased TNF-alpha in all samples. There was no correlation between cytokine le vels and disease activity or clinical manifestations. All patients had incr eased levels of antibodies to the main components of the UlsnRNP. Both anti body levels and disease activity decreased with time. A correlation between TNF-alpha and UlsnRNP antibody levels were observed in five patients. Conclusions. Increased and fluctuating levels of IL-10 or TNF-alpha without correlation to disease activity were observed in MCTD patients. In some pa tients increased cytokine levels were observed over several years irrespect ive of disease activity indicating that they could be constitutively increa sed in these individuals.