Serum level of interferon-Gamma inducible protein-10 in juvenile systemic lupus erythematosus and rheumatoid arthritis and its relation to diseases activity

Interferon-gamma inducible protein-10 [IP-10] is supposed to act as a specific chemoattractant for Th[1] cells. It is suggested to play an important role in Th[1] dominant diseases such as systemic lupus erythematosus [SLE] and juvenile rheumatoid arthritis [JRA]. We aimed to address the issue as to whether IP-10 may have an immunological role during the activity of such rheumatic diseases of childhood, and hence, its level could be used as an indicator for their activity. The study included 30 patients with SLE, 14 and 16 patients were having active and inactive disease, respectively; among them, 22 patients were having renal involvement. Also, 28 patients with JRA were also studied with equal proportion of active and inactive disease. Twenty apparently healthy, age and sex matched children were also recruited in the study as a control group. The serum level of IP-10 was measured by ELISA technique. Anti-double stranded DNA [anti-nDNA] antibodies were detected by indirect immunofluorescence. Serum C[3] level was measured by nephelometric analysis and ESR with Westergren method. CRP was detected by latex agglutination test. Serum IP-10 levels were markedly increased in SLE patients and cases with active and inactive disease, compared with controls [p<0.001, <0.001 and <0.01, respectively], with much higher increases in patients with active than inactive disease [p<0.001]. ESR showed the same findings as IP-10 in contrary to C3 levels which were significantly decreased in active than inactive SLE [p<0.05]. Serum IP-10 levels in patients with active SLE correlated negatively with C[3] levels [p<0.01] and positively with ESR [p<0.05]. Disease activity was more evident in presence of anti-nDNA antibodies [83.3%] with higher levels of IP-10 and ESR and lower levels of C3 in those cases having the antibodies [p<0.001, <0.002 and <0.001, respectively]. IP-10 levels were significantly decreased whereas C[3] levels were significantly increased in SLE patients with renal involvement [73.3%], comparing to those without renal involvement [26.7%] [p<0.01 and <0.001, respectively], but ESR did not differ between both subsets. Disease activity was more evident in non-renal subset [75%]. All non-renal patients in activity were having anti-nDNA antibodies, while 50% of those in activity and with renal involvement were having positive results. Also, patients with renal involvement and in activity showed the same results found in all patients with renal affection, in comparison to those in activity and with non-renal involvement [p<0.001 for IP-10 and <0.01 for C[3]]. Although serum IP-10 levels were also elevated among patients with JRA as well as cases with active disease, compared to controls [p<0.01 and <0.001, respectively], it did not differ between cases with active and inactive disease, as was shown with ESR, being significantly elevated in cases with active JRA [p<0.01]. However, there was significant positive correlation between both parameters among patients with active disease [p<0.05]. Also, IP-10 and ESR levels did not alter in parallel to the presence of CRP which was detected in 71.4% of cases with JRA, 50% of them were in activity. Serum IP-10 ad ESR levels were not differ statistically between patients with either SLE or JRA, even in the presence of activity. Serum IP-10 level is elevated in common rheumatic diseases of childhood, SLE and JRA. It could play an important immunological role in the pathogenesis of these diseases. IP-10 levels can be considered a good indicator for the activity of SLE as C[3], anti-nDNA antibodies and ESR, but with higher sensitivity than C[3] and anti-nDNA antibodies. So, it can be used as a sensitive marker for monitoring disease activity. On the other hand, ESR is a more sensitive indicator than serum IP-10 and CRP for detecting and monitoring the activity of JRA