ORIGINAL ARTICLE: Effect of Progesterone on Proinflammatory Cytokine Production by Monocytes Stimulated with Pathogens Associated with Preterm birth

Problem A number of clinical trials have demonstrated that supplemental progesterone (P₄) can prevent preterm birth. Although P₄ can decrease the production of mediators of inflammation by lipopolysaccharide (LPS)‐stimulated macrophages, a majority of infections associated with preterm birth are due to Ureaplasma urealyticum, which does not contain LPS. Therefore, we studied whether P₄ could lower the production of proinflammatory cytokines by monocytes stimulated with U. urealyticum. Method of study Human monocytes (THP‐1 cells) were treated with P₄ and then stimulated with heat‐killed Escherichia coli or U. urealyticum. Cytokine concentrations in the conditioned medium were then measured by ELISA and relative viability of the cells was assessed colorimetrically. The impact of P₄ on interleukin (IL)‐1β, tumor necrosis factor‐α (TNF‐α) and IL‐8 production was assessed by comparing levels across different P₄ dosages and organism concentrations. Results Both organisms increased IL‐1β, TNF‐α and IL‐8 production in a dose‐dependent manner. P₄ enhanced the production of IL‐1β and IL‐8, but inhibited TNF‐α production by monocytes stimulated with either organism. Conclusion P₄ modulates cytokine production by E. coli and U. urealyticum‐stimulated monocytes in a similar manner and is not strictly immunosuppressive. This suggests that P₄ does not prevent preterm birth by simply suppressing bacteria‐stimulated cytokine production.     

Selective effects of Lactobacillus casei Shirota on T cell activation, natural killer cell activity and cytokine production

Modulation of host immunity is an important potential mechanism by which probiotics confer health benefits. This study was designed to investigate the effects of a probiotic strain, Lactobacillus casei Shirota (LcS), on immune function using human peripheral blood mononuclear cells (PBMC) in vitro. In addition, the role of monocytes in LcS‐induced immunity was also explored. LcS promoted natural killer (NK) cell activity and preferentially induced expression of CD69 and CD25 on CD8 ⁺ and CD56 ⁺ subsets in the absence of any other stimulus. LcS also induced production of interleukin (IL)‐1β, IL‐6, tumour necrosis factor (TNF)‐α, IL‐12 and IL‐10 in the absence of lipopolysaccharide (LPS). In the presence of LPS, LcS enhanced IL‐1β production but inhibited LPS‐induced IL‐10 and IL‐6 production, and had no further effect on TNF‐α and IL‐12 production. Monocyte depletion reduced significantly the impact of LcS on lymphocyte activation, cytokine production and natural killer (NK) cell activity. In conclusion, LcS activated cytotoxic lymphocytes preferentially in both the innate and specific immune systems, which suggests that LcS could potentiate the destruction of infected cells in the body. LcS also induced both proinflammatory and anti‐inflammatory cytokine production in the absence of LPS, but in some cases inhibited LPS‐induced cytokine production. Monocytes play an important role in LcS‐induced immunological responses.     

The Nlrp3 inflammasome,IL‐1β, and neutrophil recruitment are required for susceptibility to a nonhealing strain of Leishmania major in C57BL/6 mice

Infection of C57BL/6 mice with most Leishmania major strains results in a healing lesion and clearance of parasites from the skin. Infection of C57BL/6 mice with the L. major Seidman strain (LmSd), isolated from a patient with chronic lesions, despite eliciting a strong Th1 response, results in a nonhealing lesion, poor parasite clearance, and complete destruction of the ear dermis. We show here that in comparison to a healing strain, LmSd elicited early upregulation of IL‐1β mRNA and IL‐1β‐producing dermal cells and prominent neutrophil recruitment to the infected skin. Mice deficient in Nlrp3, apoptosis‐associated speck‐like protein containing a caspase recruitment domain, or caspase‐1/11, or lacking IL‐1β or IL‐1 receptor signaling, developed healing lesions and cleared LmSd from the infection site. Mice resistant to LmSd had a stronger antigen‐specific Th1 response. The possibility that IL‐1β might act through neutrophil recruitment to locally suppress immunity was supported by the healing observed in neutropenic Genista mice. Secretion of mature IL‐1β by LmSd‐infected macrophages in vitro was dependent on activation of the Nlrp3 inflammasome and caspase‐1. These data reveal that Nlrp3 inflammasome‐dependent IL‐1β, associated with localized neutrophil recruitment, plays a crucial role in the development of a nonhealing form of cutaneous leishmaniasis in conventionally resistant mice.     

Effects of Leishmania major clones showing different levels of virulence on infectivity, differentiation and maturation of human dendritic cells

Leishmania parasites and dendritic cell interactions (DCs) play an essential role in initiating and directing T cell responses and influence disease evolution. These interactions may vary depending on Leishmania species and strains. To evaluate the correlation between Leishmania major (Lm) virulence and in-vitro human DC response, we compared the ability of high (HV) and low virulent (LV) Lm clones to invade, modulate cytokine production and interfere with differentiation of DCs. Clones derived from HV and LV (HVΔlmpdi and LVΔlmpdi), and deleted for the gene coding for a Lm protein disulphide isomerase (LmPDI), probably involved in parasite natural pathogenicity, were also used. Unlike LV, which fails to invade DCs in half the donors, HV promastigotes were associated with a significant increase of the infected cells percentage and parasite burden. A significant decrease of both parameters was observed in HVΔlmpdi-infected DCs, compared to wild-type cells. Whatever Lm virulence, DC differentiation was accompanied by a significant decrease in CD1a expression. Lm clones decreased interleukin (IL)-12p70 production similarly during lipopolysaccharide (LPS)-induced maturation of DCs. LPS stimulation was associated with a weak increase in tumour necrosis factor (TNF)-α and IL-10 productions in HV-, HVΔlmpdi- and LVΔlmpdi-infected DCs. These results indicate that there is a significant variability in the capacity of Lm clones to infect human DCs which depends upon their virulence, probably involving LmPDI protein. However, independently of their virulence, Lm clones were able to down-regulate CD1a expression during DC differentiation and IL-12p70 production during DC maturation, which may favour their survival.     

Inhibition of neutrophil-mediated production of reactive oxygen species (ROS) by endothelial cells is not impaired in anti-neutrophil cytoplasmic autoantibodies (ANCA)-associated vasculitis patients

Leucocyte transendothelial migration is strictly regulated to prevent undesired inflammation and collateral damage of endothelial cells by activated neutrophils/monocytes. We hypothesized that in anti‐neutrophil cytoplasmic autoantibodies (ANCA)‐associated vasculitis (AAV) patients' dysregulation of this process might underlie vascular inflammation. Peripheral blood mononuclear cells (PBMC) and neutrophils from AAV patients (n = 12) and healthy controls (HC, n = 12) were isolated. The influence of human umbilical vein endothelial cells (HUVEC) on neutrophil/monocytes function was tested by N‐formyl‐methionyl‐leucyl‐phenyl‐alanine (fMLP)‐ and phorbol 12‐myristate 13‐acetate (PMA)‐mediated ROS production, degranulation and interleukin (IL)‐8 production. In addition, the ability of lipopolysaccharide (LPS)‐stimulated PBMC to produce tumour necrosis factor (TNF)‐α in the presence or absence of HUVEC was tested. HUVEC inhibited ROS production dose‐dependently by fMLP‐stimulated neutrophils but did not influence degranulation. No differences between neutrophils from HC and AAV were found. However, in only one active patient was degranulation inhibited significantly by HUVEC only before cyclophosphamide treatment, but not 6 weeks later. Co‐cultures of HUVEC with LPS‐stimulated neutrophils/monocytes increased IL‐8 production while TNF‐α production was inhibited significantly. There was no apparent difference between AAV patients and HC in this respect. Our findings demonstrate that HUVEC are able to inhibit ROS and modulate cytokine production upon stimulation of neutrophils or monocytes. Our data do not support the hypothesis that endothelial cells inhibit ROS production of neutrophils from AAV patients inadequately. Impaired neutrophil degranulation may exist in active patients, but this finding needs to be confirmed.     

Innate immune responses to human rotavirus in the neonatal gnotobiotic piglet disease model

Intestinal and systemic dendritic cell (DC) frequencies, serum and small intestinal content cytokines and uptake/binding of human rotavirus (HRV) virus‐like particles (VLP) were studied in HRV acutely infected or mock‐inoculated neonatal gnotobiotic piglets. Intestinal, mesenteric lymph node (MLN) and splenic plasmacytoid DCs (pDCs), conventional DCs (cDCs) and macrophages/monocytes were assessed by flow cytometry. In infected pigs, serum and small intestinal content interferon‐α (IFN‐α) were highest, interleukin‐12 (IL‐12) was lower and IL‐10, tumour necrosis factor‐α and IL‐6 were minimal. Compared with mock‐inoculated piglets, frequencies of total intestinal DCs were higher; splenic and MLN DC frequencies were lower. Most intestinal pDCs, but few cDCs, were IFN‐α⁺ and intestinal macrophages/monocytes were negative for IFN‐α. Serum IFN‐α levels and IFN‐α⁺ intestinal pDCs were highly correlated, suggesting IFN‐α production in vivo by intestinal pDCs (r = 0·8; P < 0·01). The intestinal pDCs and cDCs, but not intestinal macrophages/monocytes, of HRV‐infected piglets showed significantly lower VLP uptake/binding compared with mock‐inoculated piglets, suggesting higher activation of pDCs and cDCs in infected piglets. Both intestinal pDCs and cDCs were activated (IFN‐α⁺ and lower VLP binding) after HRV infection, suggesting their role in induction of HRV‐specific immunity. Dose‐effects of HRV on serum IFN‐α and IFN‐α⁺ DCs were studied by infecting piglets with 100‐fold higher HRV dose. A high dose increased parameters associated with inflammation (diarrhoea, intestinal pathology) but serum IFN‐α and IFN‐α⁺ DCs were similar between both groups. The pDCs have both anti‐ and pro‐inflammatory functions. Stimulation of the anti‐inflammatory effects of pDCs after the high dose, without increasing their pro‐inflammatory impacts, may be critical to reduce further immunopathology during HRV infection.     

Expression and regulation of interleukin-33 in human monocytes

Interleukin‐33 (IL‐33) is an IL‐1 family cytokine that has a role in regulating T helper type 2 cytokines and mast cell development. Expression of IL‐33 is also associated with chronic inflammatory conditions such as rheumatoid arthritis. However, there is little information regarding IL‐33 in myeloid cell immune responses, which are important in immunity and inflammation. We therefore investigated the expression, intracellular location and regulation of myeloid cell IL‐33 by lipopolysaccharide (LPS) from Escherichia coli and the periodontal pathogen Porphyromonas gingivalis. We detected IL‐33 messenger RNA in the human promonocytic cell line THP‐1, in monocytes derived from these cells and in primary human monocytes. However, IL‐33 was not expressed in primary monocyte‐derived dendritic cells. Stimulation of monocytes with E. coli LPS (Toll‐like receptor 4 agonist) and LPS from P. gingivalis (Toll‐like receptor 2 agonist) up‐regulated IL‐33 at both the messenger RNA and protein levels but IL‐1β and tumour necrosis factor‐α had no effect. The IL‐33 protein was mainly found in the cytoplasm of monocytes with no evidence of nuclear translocation in stimulated cells. Furthermore, no IL‐33 secretion was detected after stimulation with LPS and/or ATP. These data indicate that the function, if any, of IL‐33 in activated monocytes is primarily intracellular. Interestingly, immunofluorescence analysis indicated that IL‐33 was sequestered in the nucleus of monocytes undergoing apoptosis but released into the extracellular milieu by LPS‐stimulated cells in which necrosis had been induced by freeze–thawing. Therefore, this endorses the view that IL‐33 may function as an ‘alarmin’ and have a role in signalling cellular damage and inflammatory disease pathogenesis through release from damaged or necrotic cells.     

Immunoregulatory potential of exopolysaccharide from Lactobacillus rhamnosus KL37: effects on the production of inflammatory mediators by mouse macrophages

The ability to produce exopolysaccharides (EPS) is widespread among lactobacilli including Lactobacillus rhamnosus, the commonly used probiotic bacteria. Exopolysaccharides are a major component of the bacterial biofilm with a well‐documented impact on adherence of bacteria to host cells. However, their immunoregulatory properties are unknown. The aim of this study was to examine the immunostimulatory potential of EPS derived from L. rhamnosus KL37. We investigated the effect of EPS on the production of inflammatory mediators by mouse peritoneal macrophages and compared it with the effect of Lipopolysaccharide (LPS). Exopolysaccharides, at concentrations higher than those of LPS, stimulated production of both pro‐inflammatory (TNF‐α, IL‐6, IL‐12) and anti‐inflammatory (IL‐10) cytokines. Interestingly, analysis of the balance of TNF‐α/IL‐10 production showed a potential pro‐inflammatory effect of EPS. Furthermore, our data demonstrate that exposure of macrophages to LPS induced a state of hyporesponsiveness, as indicated by reduced production of TNF‐α after restimulation with either LPS or EPS (‘cross‐tolerance’). By contrast, EPS could make cells tolerant only to subsequent stimulation by the same stimulus. We also examined the relationship between TNF‐α production and activation of mitogen‐activated protein kinases (MAPKs) by EPS and LPS. Pretreatment of macrophages with specific inhibitors of p38 and ERK MAPKs reduced TNF‐α production induced by both stimuli to the same extent. In conclusion, these data demonstrate that EPS can effectively stimulate production of inflammatory mediators by macrophages in vitro. However, to predict whether EPS could be clinically useful as an immunomodulatory agent, further in vivo studies with highly purified EPS are necessary.     

Dendritic cells, pro-inflammatory responses, and antigen presentation in a rodent malaria infection

Summary: An infection of mice with Plasmodium chabaudi is characterized by a rapid and marked inflammatory response with a rapid but regulated production of interleukin‐12 (IL‐12), tumor necrosis factor‐α (TNF‐α), and interferon‐γ (IFN‐γ). Recent studies have shown that dendritic cells (DCs) are activated in vivo in the spleen, are able to process and present malaria antigens during infection, and may provide a source of cytokines that contribute to polarization of the CD4 T‐cell response. P. chabaudi‐infected erythrocytes are phagocytosed by DCs, and peptides of malaria proteins are presented on major histocompatibility complex (MHC) class II. The complex disulfide‐bonded structure of some malaria proteins can impede their processing in DCs, which may affect the magnitude of the CD4 T‐cell response and influence T‐helper 1 (Th1) or Th2 polarization. DCs exhibit a wide range of responses to parasite‐infected erythrocytes depending on their source, their maturational state, and the Plasmodium species or strain. P. chabaudi‐infected erythrocytes stimulate an increase in the expression of costimulatory molecules and MHC class II on mouse bone marrow‐derived DCs, and they are able to induce the production of pro‐inflammatory cytokines such as IL‐12, TNF‐α, and IL‐6, thus enhancing the Th1 response of naïve T cells. IFN‐γ and TNF‐α play a role in both protective immunity and the pathology of the infection, and the inflammatory disease may be regulated by IL‐10 and transforming growth factor‐β. It will therefore be important to elucidate the host and parasite molecules that are involved in activation or suppression of the DCs and to understand the interplay between these opposing forces on the host response in vivo during a malaria infection.     

Manipulation of mitogen-activated protein kinase/nuclear factor-κB-signaling cascades during intracellular Toxoplasma gondii infection

Summary: The intracellular protozoan Toxoplasma gondii exerts profound effects on nuclear factor‐κB (NF‐κB)‐ and mitogen‐activated protein kinase (MAPK)‐signaling cascades in macrophages. During early infection, nuclear translocation of NF‐κB is blocked, and later, the cells display defects in lipopolysaccharide (LPS)‐induced MAPK phosphorylation after undergoing initial activation in response to Toxoplasma itself. Infected macrophages that are subjected to triggering through Toll‐like receptor 4 (TLR4) with LPS display defective production of tumor necrosis factor‐α and IL‐12 (IL‐12) that likely reflects interference with NF‐κB‐ and MAPK‐signaling cascades. Nevertheless, T. gondii possesses molecules that themselves induce eventual proinflammatory cytokine synthesis. For interleukin‐12, this occurs through both myeloid differentiation factor 88‐dependent and chemokine receptor CCR5‐dependent pathways. The balance between activation and interference with proinflammatory signaling is likely to reflect the need to achieve an appropriate level of immunity that allows the host and parasite to maintain a stable interaction.     

Combined cell wall polysaccharide,mycotoxin and bacterial lipopolysaccharide exposure and inflammatory cytokine responses

Human exposure to environmental microbes occurs regularly. Microbial compounds may interact with each other to affect cellular responses. We hypothesized that interactions between microbial compounds could modulate inflammatory cytokine responses in vitro. We investigated monocyte production of the pro‐inflammatory cytokine tumour necrosis factor‐α (TNF‐α) and the regulatory cytokine interleukin‐10 (IL‐10) after combined exposure to the fungal cell wall polysaccharide mannan and to the β‐glucan laminarin, the mycotoxin citrinin and bacterial lipopolysaccharide (LPS). Interactions between the cell wall microbial compounds were estimated statistically in a general linear mixed model. We found that LPS (100 ng/ml) and the used β‐glucan (up to 1000 μg/ml) significantly interacted with each other to reduce TNF‐α production. Mannan (up to 100 μg/ml) did not interact with the β‐glucan, but interacted with LPS. IL‐10 production was induced by LPS only. The mycotoxin citrinin did not induce cytokine production, but was toxic to the cells in a dose‐ and time‐dependent manner. However, non‐toxic doses of citrinin reduced LPS‐induced IL‐10 production while LPS‐induced TNF‐α production was not similarly reduced by citrinin. In conclusion, interactions between microbial compounds can modulate cellular inflammatory cytokine production and experimental investigations of one compound at a time could give misleading conclusions about these combined effects.     

NK cells modulate the lung dendritic cell‐mediated Th1/Th17 immunity during intracellular bacterial infection

The impact of the interaction between NK cells and lung dendritic cells (LDCs) on the outcome of respiratory infections is poorly understood. In this study, we investigated the effect and mechanism of NK cells on the function of LDCs during intracellular bacterial lung infection of Chlamydia muridarum in mice. We found that the naive mice receiving LDCs from C. muridarum‐infected NK‐cell‐depleted mice (NK‐LDCs) showed more serious body weight loss, bacterial burden, and pathology upon chlamydial challenge when compared with the recipients of LDCs from infected sham‐treated mice (NK+LDCs). Cytokine analysis of the local tissues of the former compared with the latter exhibited lower levels of Th1 (IFN‐γ) and Th17 (IL‐17), but higher levels of Th2 (IL‐4), cytokines. Consistently, NK‐LDCs were less efficient in directing C. muridarum‐specific Th1 and Th17 responses than NK+LDCs when cocultured with CD4⁺ T cells. In NK cell/LDC coculture experiments, the blockade of NKG2D receptor reduced the production of IL‐12p70, IL‐6, and IL‐23 by LDCs. The neutralization of IFN‐γ in the culture decreased the production of IL‐12p70 by LDCs, whereas the blockade of TNF‐α resulted in diminished IL‐6 production. Our findings demonstrate that NK cells modulate LDC function to elicit Th1/Th17 immunity during intracellular bacterial infection.     

F1 Cross‐Breed Between Susceptible BALB/c and Resistant Swiss mice Infected with Leishmania major Exhibit an Intermediate Phenotype for Lesion Sizes and Type 1 Cytokines but Show Low Level of Total IgG Antibodies

Our current understanding of the host immune response during leishmaniases largely derives from studies performed in mice due to the intrusive techniques required to study infected human patients. Swiss mice are highly resistant to Leishmania infections in concordance with observed response in humans, while BALB/c mice indicate a high‐susceptibility phenotype. Developing a cross‐breed between BALB/c and Swiss mice may have important consequences on disease development, immune responses and parasite killing, as yet, response of the cross‐breed to Leishmania infection is superficial. The aim of the present study was to determine disease course and immune responses in F₁ cross‐breed between BALB/c and Swiss albino mice infected with L. major. Three mice groups were infected intradermally with stationary‐phase L. major parasites with parental strains (BALB/c and Swiss albino) as controls. Lesion development was monitored weekly for 8 weeks and monocyte chemotactic protein (MCP‐1), macrophage inflammatory protein (MIP‐1α), interferon‐gamma (IFN‐γ) and IgG antibody quantified by enzyme‐linked immunosorbent assay. The data were analysed using one‐way analysis of variance and Tukey–Kramer test. Results indicated F₁ mice having intermediate lesion sizes, type 1 cytokine levels and footpad parasite loads as compared to the parental strains. However, the F₁ mice had low levels of IgG antibodies and parasite burden in the spleen. (P < 0.05). This study concludes that the F₁ cross‐breed between resistant and susceptible mice may be used as a requisite model to study the role of genetics in leishmaniases and perhaps other intracellular parasites.     

RIP2/RICK‐Dependent Cytokine Production Upon Yersinia enterocolitica Infection in Macrophages with TLR4 Deficiency

Receptor‐interacting protein 2 (RIP2) is a caspase recruitment domain (CARD)‐containing serine/threonine kinase that is activated by NOD1 or NOD2 recognition of their ligands and essential for the activation of NF‐κB and mitogen‐activated protein kinase (MAPK). RIP2 has been known to play an important role in innate immune responses against certain bacterial infection. However, the role and interplay of RIP2 with TLR signalling on cytokine production in macrophages against Yersinia enterocolitica infection remains poorly understood. In the present study, we examined whether RIP2 is essential for Yersinia‐induced production of cytokines in macrophages. Our results showed that naïve RIP2‐deficient macrophages produced similar level of IL‐6, TNF‐α and IL‐10 upon Y. enterocolitica infection compared with wild‐type macrophages. However, the production of IL‐6, TNF‐α and IL‐10 by Y. enterocolitica was impaired in RIP2‐deficient macrophages after lipopolysaccharide (LPS) pretreatment, a TLR4‐tolerant condition. In addition, RIP2 inhibitors, SB203580, PP2, and gefitinib, reduced IL‐6 production in TLR4‐deficient macrophages in response to Y. enterocolitica, whereas they did not affect the cytokines production in WT cells. These results demonstrate that RIP2 may play an important role in proinflammatory cytokine production in macrophages at the absence of TLR signalling.     

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.     

Dual role of monocyte‐derived dendritic cells in Trypanosoma cruzi infection

Pathogens can cause inflammation when inoculated into the skin. The vector‐transmitted protozoan parasite Trypanosoma cruzi induces poor cellular‐infiltration and disseminates, causing high mortality in the experimental model. Here, we characterized the inflammatory foci at the parasite inoculation site and secondary lymphoid organs using a murine model. While no macrophages and few neutrophils and monocytes (Mo) were recruited into the skin, T. cruzi infection elicited the mobilization of Ly6C⁺ Mo to draining lymph nodes and spleen. Over time, this population became enriched in CD11b⁺Ly6C⁺CD11c⁺MHCII⁺CD86⁺ cells resembling inflammatory dendritic cells (DCs). Adoptive transfer of Ly6C⁺ Mo purified from the bone marrow of CD11c‐GFP transgenic mice confirmed the monocytic origin of Ly6C⁺ DCs found in the spleen of infected animals. Isolated Mo‐derived cells not only produced TNF‐α and nitric oxide, but also IL‐10 and displayed a poor capacity to induce lymphoproliferation. Ablation of Mo‐derived cells by 5‐fluorouracil confirmed their dual role during infection, limiting the parasite load by inducible nitric oxide synthase‐related mechanisms and negatively affecting the development of anti‐parasite T‐cell response. This study demonstrated that consistent with their antagonistic properties, these cells not only control the parasite spreading but also its persistence in the host.     

Association of ESAT‐6/CFP‐10‐induced IFN‐γ, TNF‐α and IL‐10 with clinical tuberculosis: evidence from cohorts of pulmonary tuberculosis patients,household contacts and community controls in an endemic setting

Mycobacterium tuberculosis (Mtb) early secreted protein antigen 6 (ESAT‐6) and culture filtrate protein 10 (CFP‐10) are among candidate vaccines against tuberculosis (TB). Results of experimental animal models show that these antigens are associated with induction of strong T cell immunity [interferon (IFN)‐γ production], while others report that these proteins as virulent factors involved in pathogenicity of Mtb infection. However, the role of ESAT‐6/CFP‐10 during natural Mtb infections in humans has not been established. In this paper we present results of a longitudinal study from an Mtb‐infected human population from an endemic setting. Whole blood assay was used to determine levels of IFN‐γ, tumour necrosis factor (TNF)‐α and interleukin (IL)‐10 against rESAT‐6/CFP‐10 in TB patients, household contacts and community controls. The levels of IFN‐γ, TNF‐α and IL‐10 against rESAT‐6/CFP‐10 at baseline were significantly higher in patients and community controls than in household contacts. In patients, no significant difference was observed in the level of these cytokines before and after chemotherapy whereas, in contacts, the level of these cytokines increased significantly and progressively over time. The study shows that the levels of IFN‐γ, TNF‐α and IL‐10 against rESAT‐6/CFP‐10 are depressed during Mtb infection or exposure but are elevated during clinical TB. Our findings from a study of naturally infected human population suggest that IFN‐γ, TNF‐α and IL‐10 against rESAT‐6/CFP‐10 are markers for clinical TB but not for protective immunity.