Toll-like receptor (TLR) 2-mediated innate immunity is an important defense system against Mycobacterium tuberculosis infection. Studies on TLR2 protein expression and downstream cytokines in tuberculosis patients are lacking. TLR2 expression in the peripheral blood monocytes of 87 tuberculosis patients and 94 healthy subjects was evaluated using flow cytometry. TLR2 expression and its downstream cytokines, including interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-alpha, and interferon-gamma, were correlated with the clinical manifestations and outcomes of tuberculosis. The TLR2 expression in peripheral blood monocytes was higher in tuberculosis patients than in healthy subjects. Among the tuberculosis patients, those aged ≥70 years with disseminated tuberculosis or aged <70 years with symptom duration ≥14 days had lower initial TLR2 expression. After two months of treatment, TLR2 expression decreased in most patients, except in those whose sputum samples remained culture-positive for M. tuberculosis. Proportional hazards regression analyses revealed that high initial TLR2 expression and IL-10 plasma level were associated with shorter survival. TLR2 may play an important role in the course of tuberculosis. Its expression on peripheral blood monocytes and the plasma level of the downstream anti-inflammatory cytokine IL-10 may be important outcome predictors and have potential use in the management of tuberculosis patients.

This study was undertaken to isolate active secondary metabolites from immunostimulatory Alcaligenes faecalis FY‐3 and evaluate their activities using grass carp Ctenopharyngodon idella kidney (CIK) cells. By applying chromatography techniques and successive recrystallization, three purified metabolites were obtained and identified by spectral data (mass spectrometry and nuclear magnetic resonance) as: (1) phenylacetic acid, (2) p‐hydroxyphenylacetylamide and (3) cyclo‐(Gly‐L‐Pro). CIK cells were stimulated by different concentrations (1, 10 and 100 μg/ml) of the isolated compounds, and expression of MyD88, IL‐1β, TNF‐α, type I‐IFN and IL‐8 genes at different time points (2, 8 and 24 h) post‐stimulation was quantified by real‐time PCR. The known immunostimulatory agent lipopolysaccharide (LPS) was used as a positive control. To analyse whether these compounds are toxic to the cells, the methyl tetrazolium assay was employed to measure changes in cell viability. The obtained results revealed that transcribing level of MyD88, an important adaptor molecule in toll‐like receptor signalling pathway, was augmented remarkably by all the three isolated compounds and LPS as early as 2‐h exposure. These compounds also induced gene expression of cytokines such as IL‐1β, TNF‐α and type I‐IFN. Under the experimental conditions, none of the test compounds is toxic to the CIK cells. These findings demonstrate that the immunostimulatory properties of the three metabolites [phenylacetic acid, p‐hydroxyphenylacetylamide and cyclo‐(Gly‐L‐Pro)] from A. faecalis FY‐3 in CIK cells and highlight the potential of using these metabolites as immunostimulants in fish aquaculture.