Synergistic effect of interleukin‐17 and tumour necrosis factor‐α on inflammatory response in hepatocytes through interleukin‐6‐dependent and independent pathways

The proinflammatory cytokines interleukin (IL)‐17 and tumour necrosis factor (TNF)‐α are targets for treatment in many chronic inflammatory diseases. Here, we examined their role in liver inflammatory response compared to that of IL‐6. Human hepatoma cells (HepaRG, Huh7.5 and HepG2 cells) and primary human hepatocytes (PHH) were cultured with IL‐6, IL‐17 and/or TNF‐α. To determine the contribution of the IL‐6 pathway in the IL‐17/TNF‐α‐mediated effect, an anti‐IL‐6 receptor antibody was used. IL‐17 and TNF‐α increased in synergy IL‐6 secretion by HepaRG cells and PHH but not by Huh7.5 and HepG2 cells. This IL‐17/TNF‐α synergistic cooperation enhanced the levels of C‐reactive protein (CRP) and aspartate aminotransferase (ASAT) in HepaRG cell and PHH cultures through the induction of IL‐6. IL‐17/TNF‐α also up‐regulated IL‐8, monocyte chemoattractant protein (MCP)‐1 and chemokine (C‐C motif) ligand 20 (CCL20) chemokines in synergy through an IL‐6‐independent pathway. Interestingly, first exposure to IL‐17, but not to TNF‐α, was crucial for the initiation of the IL‐17/TNF‐α synergistic effect on IL‐6 and IL‐8 production. In HepaRG cells, IL‐17 enhanced IL‐6 mRNA stability resulting in increased IL‐6 protein levels. The IL‐17A/TNF‐α synergistic effect on IL‐6 and IL‐8 induction was mediated through the activation of extracellular signal‐regulated kinase (ERK)‐mitogen‐activated protein kinase, nuclear factor‐κB and/or protein kinase B (Akt)–phosphatidylinositol 3‐kinase signalling pathways. Therefore, the IL‐17/TNF‐α synergistic interaction mediates systemic inflammation and cell damage in hepatocytes mainly through IL‐6 for CRP and ASAT induction. Independently of IL‐6, the IL‐17A/TNF‐α combination may also induce immune cell recruitment by chemokine up‐regulation. IL‐17 and/or TNF‐α neutralization can be a promising therapeutic strategy to control both systemic inflammation and liver cell attraction.     

Combination use of immune complexes and a Ca2+ channel blocker azelnidipine enhances interleukin‐12 p40 secretion without T helper type 17 cytokine secretion in human monocyte‐derived dendritic cells

Immune complexes (ICs) improve the capacity of priming specific CD8⁺ cytotoxic T cell responses of dendritic cells (DCs). ICs induce phosphorylation of mitogen‐activated protein kinases (MAPK) and calcium influx, although the precise regulating mechanism still remains unclear. In the present study, we investigated the effect of a Ca2⁺ channel blocker on the phosphorylation of p38 MAPK and extracellular signal‐regulated kinase (ERK) in immature monocyte‐derived DCs stimulated with lipopolysaccharide (LPS) or LPS‐ICs, and the production of interleukin (IL)‐12 family members (p40, p70, IL‐23), T helper type 17 (Th17) cytokines (IL‐6 and IL‐23), tumour necrosis factor (TNF)‐α and IL‐10 were also investigated. In comparison with LPS stimulation, LPS‐ICs stimulation enhanced p38 MAPK phosphorylation significantly, which was associated with an increase in IL‐12 p40 monomer/homodimer secretion. LPS‐ICs also enhanced TNF‐α and IL‐6 secretion, but suppressed IL‐23 secretion. The use of azelnidipine (Aze), a long‐acting L‐type Ca2⁺ channel blocker with a high lipid solubility, suppressed p38 MAPK phosphorylation stimulated with LPS or LPS‐ICs, but surprisingly enhanced IL‐12 p40 monomer/homodimer secretion stimulated with LPS‐ICs. This IL‐12 p40 secretion‐enhancing effect was not accompanied by IL‐10 or IL‐23 production, but was associated with ERK phosphorylation. The use of Aze did not affect IL‐12 p70 production. These results suggest that the use of Aze enhances ICs‐mediated IL‐12 p40 secretion without additional IL‐23 secretion. Therefore, the use of Aze and ICs could be a new therapeutic approach to immunomolecular therapy, as it does not cause Th17 differentiation which induces autoimmunity or reduces anti‐tumour immunity.     

Glucocorticoid sensitivity of lipopolysaccharide‐stimulated chronic obstructive pulmonary disease alveolar macrophages

It has been reported that alveolar macrophages from patients with chronic obstructive pulmonary disease (COPD) display glucocorticoid (Gc) resistance. The Gc sensitivity of inflammatory mediators released by COPD macrophages may vary. The objective of this study was to identify Gc‐insensitive inflammatory mediators produced by lipopolysaccharide (LPS)‐stimulated alveolar macrophages from COPD patients. LPS‐stimulated alveolar macrophages from 15 COPD patients, nine smokers (S) and nine healthy non‐smokers (HNS) were stimulated with LPS with or without dexamethasone (100 and 1000 nM). Luminex and enzyme‐linked immunosorbent assay were used to measure 23 inflammatory mediators. After LPS stimulation there were lower levels of inflammatory mediators in COPD patients and S compared to HNS. There was no difference between groups for the effects of dexamethasone at either concentration (P > 0·05 for all comparisons). Tumour necrosis factor (TNF)‐α, interleukin (IL)‐6 and growth‐related oncogene (GRO)‐α displayed the greatest sensitivity to dexamethasone in COPD patients, while IL‐8, granulocyte–macrophage colony‐stimulating factor (GM‐CSF) and granulocyte colony‐stimulating factor (G‐CSF) were the least sensitive. COPD macrophages have a reduced response to LPS. Gc sensitivity was similar in COPD macrophages compared to controls. We identify some Gc‐insensitive cytokines, including GM‐CSF, G‐CSF and IL‐8, that may be involved in the progression of airway inflammation in COPD patients.     

FluoroSpot Analysis of TLR‐Activated Monocytes Reveals Several Distinct Cytokine‐Secreting Subpopulations

Monocytes have long been considered a heterogeneous group of cells both in terms of morphology and function. In humans, three distinct subsets have been described based on their differential expression of the cell surface markers CD14 and CD16. However, the relationship between these subsets and the production of cytokines has for the most part been based on ELISA measurements, making it difficult to draw conclusions as to their functional profile on the cellular level. In this study, we have investigated lipoteichoic acid (LTA)‐ and lipopolysaccharide (LPS)‐induced cytokine secretion by monocytes using the FluoroSpot technique. This method measures the number of cytokine‐secreting cells on the single‐cell level and uses fluorescent detection, allowing for the simultaneous analysis of two cytokines from the same population of isolated cells. By this approach, human monocytes from healthy volunteers could be divided into several subgroups as IL‐1β, IL‐6, TNF‐α and MIP‐1β were secreted by larger populations of responding cells (25.9–39.2%) compared with the smaller populations of GM‐CSF (9.1%), IL‐10 (1.3%) and IL‐12p40 (1.2%). Furthermore, when studying co‐secretion in FluoroSpot, an intricate relationship between the monocytes secreting IL‐1β and/or IL‐6 and those secreting TNF‐α, MIP‐1β, GM‐CSF, IL‐10 and IL‐12p40 was revealed. In this way, dissecting the secretion pattern of the monocytes in response to TLR‐2 or TLR‐4 stimulation, several subpopulations with distinct cytokine‐secreting profiles could be identified.     

The impact of disease activity and tumour necrosis factor‐α inhibitor therapy on cytokine levels in juvenile idiopathic arthritis

The aim of this study was to evaluate prospectively cytokine levels and disease activity in juvenile idiopathic arthritis (JIA) patients treated with and without tumour necrosis factor (TNF)‐α inhibitors. TNF‐α inhibitor‐naive JIA subjects were followed prospectively for 6 months. Cytokine levels of TNF‐α, interleukin (IL)?1β, IL‐6, IL‐8, IL‐10 and IL‐17 were measured at baseline for JIA subjects and healthy controls (HCs). Cytokine levels were then measured at four time‐points after initiation of TNF‐α inhibition for anti‐TNF‐α‐treated (anti‐TNF) JIA subjects, and at two subsequent time‐points for other JIA (non‐TNF) subjects. JIA disease activity by Childhood Health Assessment Questionnaire (CHAQ) disability index/pain score and physician joint count/global assessment was recorded. Sixteen anti‐TNF, 31 non‐TNF and 16 HCs were analysed. Among JIA subjects, those with higher baseline disease activity (subsequent anti‐TNFs) had higher baseline TNF‐α, IL‐6 and IL‐8 than those with lower disease activity (non‐TNFs) (P < 0·05). TNF‐α and IL‐10 increased, and IL‐6 and IL‐8 no longer remained significantly higher after TNF‐α inhibitor initiation in anti‐TNF subjects. Subgroup analysis of etanercept versus adalimumab‐treated subjects showed that TNF‐α and IL‐17 increased significantly in etanercept but not adalimumab‐treated subjects, despite clinical improvement in both groups of subjects. JIA subjects with increased disease activity at baseline had higher serum proinflammatory cytokines. TNF‐α inhibition resulted in suppression of IL‐6 and IL‐8 in parallel with clinical improvement in all anti‐TNF‐treated subjects, but was also associated with elevated TNF‐α and IL‐17 in etanercept‐treated subjects.     

Comparative Study of Trans‐Oral and Trans‐Tracheal Intratracheal Instillations in a Murine Model of Acute Lung Injury

Animal model is of importance to further elucidate the pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). We envisioned a possibility that there might be the differences in lipopolysaccharide (LPS)‐induced acute lung inflammation by the trans‐oral and trans‐tracheal intratracheal instillations. We compared the LPS‐induced early inflammatory responses by these two methods. The evaluative system included bronchoalveolar lavage (BAL) fluid biochemical analysis and differential cell counting, lung wet/dry weight ratio and lung histology. In vitro studies were performed on human bronchial epithelial cell line NCI‐H292 and alveolar Type II epithelial cell line A549 stimulated with LPS. Both interleukin (IL)‐8 release in the BAL fluid and IL‐8 secretions from NCI‐H292 and A549 cells were measured. We found that the trans‐tracheal intratracheal instillation promoted the LPS‐induced cell injury, neutrophil infiltration, and pulmonary edema compared to the trans‐oral one. The LPS‐induced pathological changes by the trans‐oral intratracheal instillation were characterized by pulmonary interstitial edema, but the trans‐tracheal intratracheal instillation was exudative pulmonary edema. More IL‐8 is produced from A549 cells than from NCI‐H292 cells under the treatment of LPS. The increased IL‐8 release in the BAL fluid and enhanced inflammatory responses caused by LPS may be due to more LPS delivered into the alveolar spaces by the trans‐tracheal intratracheal instillation compared to the trans‐oral one. The trans‐tracheal intratracheal instillation is proved to be more suitable to establish the murine model of ALI than the trans‐oral one and helpful to further elucidate the pathogenesis of ALI/ARDS. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.     

OK‐432‐stimulated chemokine secretion from human monocytes depends on MEK1/2, and involves p38 MAPK and NF‐κB phosphorylation,in vitro

Interaction between the immune system and cancer cells allows for the use of biological response modifiers, like OK‐432, in cancer therapy. We have studied the involvement of monocytes (MOs) in the immune response to OK‐432 by examining MCP‐1, MIP‐1α and MIP‐1β secretion, in vitro. OK‐432‐induced IL‐6/TNF‐α secretion has previously been shown to depend on mitogen‐activated protein kinases (MAPKs) ERK1/2 and p38, and we therefore investigated the role of these MAPKs in OK‐432‐induced chemokine secretion. Here we demonstrate that pharmacological MEK1/2 kinase inhibition generally impaired chemokine secretion from MOs, whereas p38 MAPK inhibition in particular reduced MIP‐1α production. Furthermore, simultaneous inhibition of MEK1/2 and Syk kinase was seen to have an additive impact on reduced MCP‐1, MIP‐1α and MIP‐1β secretion. Based on single cell flow cytometry analyses, OK‐432, lipoteichoic acid (LTA) and lipopolysaccharide (LPS) were seen to induce p38 MAPK and NF‐κB phosphorylation in MOs with different time kinetics. LTA and LPS have been shown to induce ERK1/2 phosphorylation, whereas the levels of phosphorylated ERK1/2 remained constant following OK‐432 treatment at the time points tested. Toll‐like receptors (TLRs) recognize pathogen‐associated molecular patterns, and we demonstrate increased TLR2 cell surface levels on the MO population, most profoundly following stimulation with LTA and OK‐432. Together these results indicate that modulation of MEK1/2 and p38 MAPK signalling could affect the response to OK‐432 treatment, having the potential to improve its therapeutic potential within cancer and lymphangioma treatment.     

Human β‐defensin 3 has immunosuppressive activity in vitro and in vivo

β‐defensins are antimicrobial peptides with an essential role in the innate immune response. In addition β‐defensins can also chemoattract cells involved in adaptive immunity. Until now, based on evidence from dendritic cell stimulation, human β defensin‐3 (hBD3) was considered pro‐inflammatory. We present evidence here that hBD3 lacks pro‐inflammatory activity in human and mouse primary M?. In addition, in the presence of LPS, hBD3 and the murine orthologue Defb14 (but not hBD2), effectively inhibit TNF‐α and IL‐6 accumulation implying an anti‐inflammatory function. hBD3 also inhibits CD40/IFN‐γ stimulation of M? and in vivo, hBD3 significantly reduces the LPS‐induced TNF‐α level in serum. Recent work has revealed that hBD3 binds melanocortin receptors but we provide evidence that these are not involved in hBD3 immunomodulatory activity. This implies a dual role for hBD3 in antimicrobial activity and resolution of inflammation.     

ORIGINAL ARTICLE: Profile of Peripheral Blood Neutrophil Cytokines in Diabetes Type 1 Pregnant Women and its Correlation with Selected Parameters in the Newborns

Citation Pertyńska‐Marczewska M, G?owacka E, Grodzicka A, Sobczak M, Cypryk K, Wilczyński JR., Wilczyński J. Profile of peripheral blood neutrophil cytokines in diabetes type 1 pregnant women and its correlation with selected parameters in the newborns. Am J Reprod Immunol 2010; 63: 150–160 Problem Interleukin (IL)‐12, IL‐10, tumor necrosis factor‐α (TNF‐α), IL‐6 and IL‐8 alter as pregnancy progresses, implying continuous immune regulation associated with the maintenance of pregnancy. We aimed to evaluate the peripheral blood neutrophil‐derived production of these cytokines in the course of pregnancy complicated by type 1 diabetes. Method of study These parameters were measured in samples from healthy non‐pregnant (C), diabetic non‐pregnant (D), healthy pregnant (P) and pregnant diabetic (PD) women. Results Neutrophil‐derived secretion of TNF‐α and IL‐12 increased along with progression of pregnancy in PD and P groups. The concentration of IL‐10 from lipopolysaccharide (LPS)‐stimulated neutrophils increased during the course of uncomplicated pregnancy but decreased in diabetic pregnancy. Concentration of IL‐8 decreased with the advancing gestational age in P and PD groups. LPS‐stimulated neutrophil‐derived IL‐6 concentration increased only in PD patients. Conclusion Our results show that diabetes creates pro‐inflammatory environment thus potentially influencing the outcome of pregnancy. We conclude that neutrophil‐derived cytokine production could contribute to the complications seen in pregnant women with type 1 diabetes.     

Lipopolysaccharide (LPS)‐induced Interferon (IFN)‐gamma Production by Decidual Mononuclear Cells (DMNC) is Interleukin (IL)‐2 and IL‐12 Dependent

Citation Negishi M, Izumi Y, Aleemuzzaman S, Inaba N, Hayakawa S. Lipopolysaccharide (LPS)‐induced interferon (IFN)‐gamma production by decidual mononuclear cells (DMNC) is interleukin (IL)‐2 and IL‐12 dependent. Am J Reprod Immunol 2011; 65: 20–27 Problem Th1‐shifted immune response is believed to be harmful for successful pregnancy because of activation of maternal cytotoxic T lymphocytes and natural killer cells. However, its effects on Toll‐like receptor (TLR)‐mediated innate immune response are so far unknown and this study has been undertaken to address the issue. Method of study Decidual tissues were obtained from 16 pregnant women undergoing elective termination during the first trimester pregnancy for socioeconomic reasons. Decidual Mononuclear Cells (DMNC) were stimulated with suboptimal doses of IL‐2 and IL‐12 with/without LPS, considered to be a TLR4 ligand, for 48 hr. Productions of IFN‐γ and tumor necrosis factor (TNF)‐α in culture supernatant were measured with ELISA. Results (i) IFN‐γ production was induced with LPS alone which was strongly up‐regulated in the presence of IL‐2 and IL‐12. (ii) TNF‐α was also induced by LPS but was not affected by the presence of IL‐2 and IL‐12. Conclusion IL‐2 and IL‐12 up‐regulated the production of IFN‐γ in DMNC through increasing their susceptibility to LPS. TNF‐α production is independent of such a mechanism.     

The role of IL‐28, IFN‐γ, and TNF‐α in predicting response to pegylated interferon/ribavirin in chronic HCV patients

The primary goal of HCV therapy is to achieve a sustained virological response (SVR). Many host and viral factors influence the treatment response. Cytokines play an important role in the defense against viral infections, where successful treatment of hepatitis C depends on a complex balance between pro‐ and anti‐inflammatory responses. In the present study, we investigated the relationship between the presence and percentage of some cytokines (IL‐28, IFN‐γ, and TNF‐α) regarding different clinicopathological parameters including response to therapy in chronic HCV patients using immunohistochemical technique. This study was carried out on 64 chronic HCV patients (34 responders and 30 non‐responders). Of cases, 54% showed IL‐28 expression, which was associated with low AST (p = 0.002) and low HAI score (p = 0.006). Of cases, 67 and 45% showed IFN‐γ and TNF‐α expression, respectively, where the median percentage of TNF‐α expression was higher in grade II spotty necrosis compared to grade I. Some inflammatory cytokines expressed by intrahepatic inflammatory cells in chronic HCV patients promote inflammation and injury (pro‐inflammatory) such as TNF‐α. Other cytokines aid in resolving inflammation and injury (anti‐inflammatory) such as IL‐28. The balance between these cytokines will determine the degree of inflammatory state. None of the investigated cytokines proved its clear cut role in affecting response to therapy, however, their levels varied between responders and non‐responders for further investigations to clarify.     

Impaired cytokine responses in patients with cryopyrin‐associated periodic syndrome (CAPS)

Cryopyrin‐associated periodic syndrome (CAPS) is characterized by dysregulated inflammation with excessive interleukin (IL)‐1β activation and secretion. Neonatal‐onset multi‐system inflammatory disease (NOMID) is the most severe form. We explored cytokine responses in 32 CAPS patients before and after IL‐1β blocking therapy. We measured cytokines produced by activated peripheral blood monuclear cells (PBMCs) from treated and untreated CAPS patients after stimulation for 48 h with phytohaemagglutinin (PHA), PHA plus IL‐12, lipopolysaccharide (LPS) or LPS plus interferon (IFN)‐γ. We measured IL‐1β, IL‐6, IL‐10, tumour necrosis factor (TNF), IL‐12p70 and IFN‐γ in the supernatants. PBMCs from three untreated CAPS patients were cultured in the presence of the IL‐1β blocker Anakinra. Fifty healthy individuals served as controls. CAPS patients had high spontaneous production of IL‐1β, IL‐6, TNF and IFN‐γ by unstimulated cells. However, stimulation indexes (SIs, ratio of stimulated to unstimulated production) of these cytokines to PHA and LPS were low in NOMID patients compared to controls. Unstimulated IL‐10 and IL‐12p70 production was normal, but up‐regulation after PHA and LPS was also low. LPS plus IFN‐γ inadequately up‐regulated the production of IL‐1β, IL‐6, TNF and IL‐10 in CAPS patients. In‐vitro but not in‐vivo treatment with Anakinra improved SIs by lowering spontaneous cytokine production. However, in‐vitro treatment did not improve the low stimulated cytokine levels. Activating mutations in NLRP3 in CAPS are correlated with poor SIs to PHA, LPS and IFN‐γ. The impairment in stimulated cytokine responses in spite of IL‐1β blocking therapy suggests a broader intrinsic defect in CAPS patients, which is not corrected by targeting IL‐1β.     

Inhibitory Effect of Water‐Soluble Chitosan on TNF‐α and IL‐8 Secretion from HMC‐1 Cells

Mast cells are known to play an active role as effector cells in allergic inflammation and in diverse immunological and pathological processes. Activated mast cell‐derived pro‐inflammatory cytokines are important pathologic factors of progression of allergic inflammation. In this study, we investigated whether pro‐inflammatory cytokines (TNF‐α and IL‐8) can be induced by calcium stimulation in HMC‐1 cells, and high molecular weight water‐soluble chitosan (WSC) can inhibit the production of these cytokines. We provided evidence that the secretion of TNF‐α and IL‐8 from HMC‐1 cells was induced by Ca^{2 +}‐ionophore A23187 or Ca^{2 +}‐ATPase inhibitor TSG. Treatment of WSC (10 µg/ml) prior to stimulation with calcium agonists significantly blocked the secretion of TNF‐α by 65.1% for A23187 and 87.7% for TSG. IL‐8 secretion in response to A23187 or TSG was inhibited by 49.2% for A23187 and 34.1% for TSG, respectively, compared to absence of WSC. These results suggest that WSC has potential regulatory effects on allergic inflammatory diseases by down‐modulating Ca^{2 +}‐induced mast cell activation.     

Caspase‐11 non‐canonical inflammasome: a critical sensor of intracellular lipopolysaccharide in macrophage‐mediated inflammatory responses

Inflammatory responses mediated by macrophages are part of the innate immune system, whose role is to protect against invading pathogens. Lipopolysaccharide (LPS) found in the outer membrane of Gram‐negative bacteria stimulates an inflammatory response by macrophages. During the inflammatory response, extracellular LPS is recognized by Toll‐like receptor 4, one of the pattern recognition receptors that activates inflammatory signalling pathways and leads to the production of inflammatory mediators. The innate immune response is also triggered by intracellular inflammasomes, and inflammasome activation induces pyroptosis and the secretion of pro‐inflammatory cytokines such as interleukin‐1β (IL‐1β) and IL‐18 by macrophages. Cysteine‐aspartic protease (caspase)‐11 and the human orthologues caspase‐4/caspase‐5 were recently identified as components of the ‘non‐canonical inflammasome’ that senses intracellular LPS derived from Gram‐negative bacteria during macrophage‐mediated inflammatory responses. Direct recognition of intracellular LPS facilitates the rapid oligomerization of caspase‐11/4/5, which results in pyroptosis and the secretion of IL‐1β and IL‐18. LPS is released into the cytoplasm from Gram‐negative bacterium‐containing vacuoles by small interferon‐inducible guanylate‐binding proteins encoded on chromosome 3 (GBP^chr3)‐mediated lysis of the vacuoles. In vivo studies have clearly shown that caspase‐11^−/− mice are more resistant to endotoxic septic shock by excessive LPS challenge. Given the evidence, activation of caspase‐11 non‐canonical inflammasomes by intracellular LPS is distinct from canonical inflammasome activation and provides a new paradigm in macrophage‐mediated inflammatory responses.     

Comparative analysis of spontaneous and mycobacterial antigen-induced secretion of Th1, Th2 and pro-inflammatory cytokines by peripheral blood mononuclear cells of tuberculosis patients

The cytokines produced by T helper (Th)1 cells (IFN‐γ, IL‐2 and TNF‐β) correlate with protection, whereas the cytokines released by Th2 cells (IL‐4, IL‐5) and the anti‐inflammatory cytokine IL‐10 correlate with pathogenesis of tuberculosis (TB). However, the pro‐inflammatory cytokines (IL‐1β, IL‐6, IL‐8, TNF‐α and IL‐12p70) are responsible for both protection and pathogenesis of TB. The aim of this work was to carry out a comparative analysis of cytokines present in early (day 2) and late (day 6) cultures of peripheral blood mononuclear cells (PBMCs) obtained from pulmonary tuberculosis patients. PBMCs were cultured in vitro in the absence and presence of exogenously added complex mycobacterial antigens and RD1 peptide pool. The supernatants were collected on day 2 and day 6 of culture and assayed for secreted cytokines using the flow cytomix assay. All of the cytokines, except for IL‐12p70, were spontaneously secreted by PBMCs of 27–100% TB patients, but only TNF‐α concentration was significantly higher on day 2 than day 6 (P < 0.05). Two days following antigenic stimulation, only IL‐1β, IL‐6, TNF‐α and IL‐10 were secreted in response to some mycobacterial antigens. However, 6 days later, all of the cytokines, except for IL‐2, IL‐4, IL‐5 and IL‐8, were secreted significantly in response to all complex antigens and RD1 peptides, compared with the non‐stimulated cultures (P < 0.05). In conclusion, the study shows that the longer in vitro stimulation time (6 days) was necessary for the optimal induction of IFN‐γ and TNF‐β, and practically convenient for the detection of IL‐10, IL‐1 β, TNF‐α and IL‐6.