Serum interleukin-6 levels are increased in HIV-infected patients that develop autoimmune disease during long-term follow-up

Background: Elevated IL-6 levels have been associated with both autoimmune diseases and treated HIV-seropositive (HIV+) subjects. However, few data on classic and trans-signaling IL-6 in autoimmune thyroid diseases and HIV+ subjects developing autoimmune disorders are currently available. Materials and methods: A total of 102 patients were included in the study. They were subdivided into two groups. Group A consisted in 51 HIV+ patients, who were followed-up for a period of five years in search of possible occurrence of autoimmune diseases. Ten of them, treated with antiretroviral therapy (ART), developed an autoimmune disorder, namely Hashimoto's thyroiditis, and psoriasis. Group B consisted in 51 patients affected by Hashimoto's thyroiditis (HT). Serum levels of the free form of IL-6 were analyzed by ELISA in all patients and for HIV+ patients at the beginning of the follow-up, before initiation of ART. Results: Mean serum levels of IL-6 were similar in Group A and in Group B. In Group B, IL-6 levels showed a 5.8% increase compared with assay minimum detectable dose corresponding to 1% of full serum IL-6 level. However, serum levels of free IL-6 were increased in those HIV+ patients who developed autoimmune disorders (5.8 ± 2.8 pg/ml) and in these patients, the highest levels of free IL-6 correlated with age and CD4 cellular counts. Conclusions: The present study indicates a correlation between serum free IL-6 levels and the occurrence of autoimmune disease in HIV+ population, treated with ART during a long-term follow-up. The increased levels of serum free IL-6 were observed before ART treatment was initiated, indicating that IL-6 measurement in such patients may represent an early predictor of development of autoimmune disease.