IL-6 and INF-γ levels in patients with brucellosis in severe epidemic region, Xinjiang, China

BACKGROUND: The incidence of brucellosis, which is caused by the Brucella species of bacteria, is rapidly rising worldwide; however, few studies have investigated the immune response to this pathogen and clinical biochemical features. In this paper, we examined the levels of various cytokines and inflammatory factors as well as clinical course characteristics in patients with brucellosis, in order to provide evidence for the diagnosis, assessment, and prognosis of this infectious disease. METHODS: A total of 191 brucellosis inpatients (50 acute cases and 141 chronic cases), as well as 60 healthy control subjects, were included in the analysis. We investigated changes in the levels of six cytokines (IL-4, IL-6, IL-10, IL-17, TNF-α, INF-γ) and related clinical biochemical markers in patients with acute and chronic brucellosis in Xinjiang, China. Possible factors were statistically analyzed using the t test, χ(2) test, z test and a multivariate logistic stepwise regression test. RESULTS: We found that IL-4, IL-6, IL-10, IL-17, IFN-γ, and TNF-α levels were higher in those with brucellosis than in controls (P < 0.05). With regard to disease progression, procalcitonin (PCT) and C-reactive protein (CRP) levels were significantly higher in those with an acute infection compared to chronic cases (P < 0.05). We found that the expression of all six cytokines tested was closely related to the degree of brucellosis using univariate logistic regression; however, only IL-6 and INF-γ levels were independent factors associated with the severity of brucellosis. CONCLUSIONS: Assessing cytokine levels in patients with acute and chronic brucellosis is not only useful for detecting the immune response, but can also be indicative of the severity of brucellosis. In particular, we propose IL-6 and INF-γ levels may be useful independent predictive factors in the clinical evaluation and diagnosis of brucellosis.