Shiga Toxins Stimulate Secretion of Interleukin-8 from Intestinal Epithelial Cells

In the 1980s, Shiga toxin (Stx)-producing Escherichia coli O157:H7 (STEC) was identified as a cause of hemorrhagic colitis in the United States and was found to be associated with hemolytic uremic syndrome (HUS), a microangiopathic hemolytic anemia characterized by thrombocytopenia and renal failure. The precise way that Stxs cause hemorrhagic colitis and HUS is unclear. Stxs have been thought to cause disease by killing or irreversibly harming sensitive cells through a nonspecific blockade of mRNA translation, eventually resulting in cytotoxicity by preventing synthesis of critical molecules needed to maintain cell integrity. Because STEC is noninvasive, we have been exploring the host-toxin response at the level of the gastrointestinal mucosa, where STEC infection begins. We have found that Stx is capable of interleukin-8 (IL-8) superinduction in a human colonic epithelial cell line. Despite a general blockade of mRNA translation, Stx treatment results in increased IL-8 mRNA as well as increased synthesis and secretion of IL-8 protein. Our data suggest that an active Stx A subunit is required for this activity. Ricin, which has the same enzymatic activity and trafficking pathway as Stx, has similar effects. Exploration of the effects of other protein synthesis inhibitors (cycloheximide, anisomycin) suggests a mechanism of gene regulation that is distinct from a general translational blockade. Use of the specific p38/RK inhibitor SB202190 showed that blocking of this pathway results in decreased Stx-mediated IL-8 secretion. Furthermore, Stxs induced mRNA of the primary response gene c-jun, which was subsequently partially blocked by SB202190. These data suggest a novel model of how Stxs contribute to disease, namely that Stxs may alter regulation of host cell processes in sensitive cells via activation of at least one member of the mitogen-activated protein kinase family in the p38/RK cascade and induction of c-jun mRNA. Stx-induced increases in chemokine synthesis from intestinal epithelial cells could be important in augmenting the host mucosal inflammatory response to STEC infection.     

Inducible and Constitutive In Vitro Neutrophil Chemokine Expression by Mammary Epithelial and Myoepithelial Cells

Previously, our laboratory showed that bovine and caprine mammary secretions are chemotactic and that chemoattractants found in these secretions are qualitatively different according to infection status and/or lactation stage. However, the cellular source of the chemoattractants has not been defined. In this study we used a modified Boyden chamber assay to examine the ability of previously established caprine mammary epithelial cell (CMEC) and myoepithelial cell (CMMyoEC) lines to produce chemoattractants for neutrophils. We found that CMEC culture supernatants, but not those of CMMyoEC cultures, induced in vitro neutrophil chemotaxis. Further characterization showed that chemotactic activity was produced when the cells underwent contact-induced differentiation. Neutrophil migration was chemotactic, not chemokinetic, and was augmented when the epithelial and myoepithelial cells were cocultured. Additionally, chemotactic activity was inducible by Staphylococcus aureus plus alpha-toxin, Escherichia coli, and interleukin-1β (IL-1β) in CMEC cultures. However, CMMyoEC cultures could not be induced to produce chemotactic activity. Anti-IL-8 antibody was able to block some constitutively produced chemotactic activity and chemotactic activity induced by IL-1β and S. aureus plus alpha-toxin. These results indicate that epithelial cells may play a major role in producing chemoattractants, specifically IL-8, in the mammary gland.     

The K5 Capsule of Escherichia coli Strain Nissle 1917 Is Important in Mediating Interactions with Intestinal Epithelial Cells and Chemokine Induction

Escherichia coli strain Nissle 1917 has been widely used as a probiotic for the treatment of inflammatory bowel disorders and shown to have immunomodulatory effects. Nissle 1917 expresses a K5 capsule, the expression of which often is associated with extraintestinal and urinary tract isolates of E. coli. In this paper, we investigate the role of the K5 capsule in mediating interactions between Nissle 1917 and intestinal epithelial cells. We show that the loss of capsule significantly reduced the level of monocyte chemoattractant protein 1 (MCP-1), RANTES, macrophage inflammatory protein 2α (MIP-2α), MIP-2β, interleukin-8, and gamma interferon-inducible protein 10 induction by Nissle 1917 in both Caco-2 cells and MCP-1 induction in ex vivo mouse small intestine. The complementation of the capsule-minus mutation confirmed that the effects on chemokine induction were capsule specific. The addition of purified K5, but not K1, capsular polysaccharide to the capsule-minus Nissle 1917 at least in part restored chemokine induction to wild-type levels. The purified K5 capsular polysaccharide alone was unable to stimulate chemokine production, indicating that the K5 polysaccharide was acting to mediate interactions between Nissle 1917 and intestinal epithelial cells. The induction of chemokine by Nissle 1917 was generated predominantly by interaction with the basolateral surface of Caco-2 cells, suggesting that Nissle 1917 will be most effective in inducing chemokine expression where the epithelial barrier is disrupted.A probiotic has been defined as “live microorganisms which when administered in adequate amounts confer a health benefit on the host” (20). These benefits include the balancing and restoration of the intestinal microflora, repair of intestinal barrier functions (54), expression of bacteriocins (36), immunomodulatory effects (18, 43, 47, 53), and antagonizing epithelial colonization and invasion by pathogens (2). Escherichia coli strain Nissle 1917 was isolated from the feces of a soldier who did not develop diarrhea during a severe outbreak of shigellosis (38). Despite exhibiting a serotype (O6:K5:H1) that is characteristic of E. coli strains associated with urinary tract infections, Nissle 1917 apparently is nonpathogenic (25, 53) and has been used widely in preventing infectious diarrheal diseases (7, 14, 27, 37, 52, 53), the treatment of inflammatory bowel diseases such as ulcerative colitis and Crohn''s disease (7, 23, 32, 33), and to prevent the colonization of the digestive tract of neonates by pathogens (35). Recently, there has been a growing interest in investigating the immunomodulatory effect of Nissle 1917. Previous studies showed that colonization by Nissle 1917 may lead to an alteration of the hosts'' cytokine repertoire (13, 49), increased immunoglobulin A secretion (14), lymphocyte or macrophage activation (13), the modulation of CD4⁺ clonal expansion (47), the stimulation of antimicrobial peptide production by intestinal epithelial cells (39, 52, 54), and alterations of the pro- and anti-inflammatory balance of local cytokines (49). Recently it has been shown that Nissle 1917 activates γδT cells, stimulating CXCL8 and interleukin-6 (IL-6) release but inhibiting tumor necrosis factor alpha (TNF-α) secretion (26). Following activation, Nissle 1917 induced apoptosis in activated γδT cells, indicating a key role for Nissle 1917 in interacting with the subset of T cells that operate at the interface between the adaptive and innate immune responses (26). Nissle 1917 also has been shown to express a direct anti-inflammatory activity on epithelial cells by blocking TNF-α-induced IL-8 secretion through a NF-κB-independent mechanism (28). Although the immunomodulatory effects of Nissle 1917 are well documented, the contribution of individual microbial components in mediating such effects is less well understood. So far, only a role for flagellin in mediating the induction of human β-defensin expression by Nissle 1917 has been established (44). Nissle 1917 expresses a K5 capsule on its cell surface, and a number of roles for polysaccharide capsules in the virulence of E. coli have been proposed, including resistance to phagocytosis and complement-mediated killing and the increased colonization of the host (42). In contrast, in the case of other encapsulated pathogens, it has been shown that the expression of a polysaccharide capsule can affect the induction of chemokines following attachment to host cells (6, 17, 22, 24, 40, 41, 45, 50). The aim of the present study was to investigate the role of the K5 capsule in mediating the immunomodulatory activity of Nissle 1917.     

Differential Effects of Escherichia coli Subtilase Cytotoxin and Shiga Toxin 2 on Chemokine and Proinflammatory Cytokine Expression in Human Macrophage,Colonic Epithelial,and Brain Microvascular Endothelial Cell Lines

Subtilase cytotoxin (SubAB) is the prototype of a recently emerged family of AB5 cytotoxins produced by Shiga-toxigenic Escherichia coli (STEC). Its mechanism of action involves highly specific A-subunit-mediated proteolytic cleavage of the essential endoplasmic reticulum (ER) chaperone BiP. Our previous in vivo studies showed that intraperitoneal injection of purified SubAB causes a major redistribution of leukocytes and elevated leukocyte apoptosis in mice, as well as profound splenic atrophy. In the current study, we investigated selected chemokine and proinflammatory cytokine responses to treatment with SubAB, a nontoxic derivative (SubA_A272B), or Shiga toxin 2 (Stx2) in human macrophage (U937), brain microvascular endothelial (HBMEC), and colonic epithelial (HCT-8) cell lines, at the levels of secreted protein, cell-associated protein, and gene expression. Stx2 treatment upregulated expression of chemokines and cytokines at both the protein and mRNA levels. In contrast, SubAB induced significant decreases in secreted interleukin-8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) in all three tested cell lines and a significant decrease in secreted IL-6 in HBMECs. The downregulation of secreted chemokines or cytokines was not observed in SubA_A272B-treated cells, indicating a requirement for BiP cleavage. The downregulation of secreted chemokines and cytokines by SubAB was not reflected at the mRNA and cell-associated protein levels, suggesting a SubAB-induced export defect.     

Cytokine and Chemokine Production by Human Oral and Vaginal Epithelial Cells in Response to Candida albicans

Oropharyngeal and vaginal candidiases are the most common forms of mucosal fungal infections and are primarily caused by Candida albicans, a dimorphic fungal commensal organism of the gastrointestinal and lower female reproductive tracts. Clinical and experimental observations suggest that local immunity is important in host defense against candidiasis. Accordingly, cytokines and chemokines are present at the oral and vaginal mucosa during C. albicans infections. Since mucosal epithelial cells produce a variety of cytokines and chemokines in response to microorganisms and since C. albicans is closely associated with mucosal epithelial cells as a commensal, we sought to identify cytokines and/or chemokines produced by primary oral and vaginal epithelial cells and cell lines in response to C. albicans. The results showed that proinflammatory cytokines were produced by oral and/or vaginal epithelial cells at various levels constitutively with considerable interleukin-1alpha (IL-1alpha) and tumor necrosis factor alpha, but not IL-6, produced in response to C. albicans. In contrast, Th1-type (IL-12 and gamma interferon) and Th2-type-immunoregulatory (IL-10 and transforming growth factor beta) cytokines and the chemokines monocyte chemoattractant protein 1 and IL-8 were produced in low to undetectable concentrations with little additional production in response to C. albicans. Taken together, these results indicate that cytokines and chemokines are variably produced by oral and vaginal epithelial cells constitutively, as well as in response to C. albicans, and are predominated by proinflammatory cytokines.     

Human Intestinal Epithelial Cells Respond to Cryptosporidium parvum Infection with Increased Prostaglandin H Synthase 2 Expression and Prostaglandin E2 and F2α Production

Cryptosporidium parvum is an important cause of diarrhea in humans and several animal species. Prostaglandins play a central role in regulating intestinal fluid secretion in animal models of cryptosporidiosis, but their cellular sources and mechanisms of induction are unclear. Here, we show that C. parvum infection directly activates prostaglandin H synthase 2 expression and prostaglandin E₂ and F_2α production in human intestinal epithelial cells.     

Gram Positive Bacteria Induce IL-6 and IL-8 Production in Human Alveolar Macrophages and Epithelial Cells

Background and Objective: Inhalation of dust from swine confinement buildings results in an acute inflammatory reaction in the respiratory tract. The dust has a high microbial content, dominated by Gram positive bacteria. The aim of the present study was to evaluate the significance of bacteria in the induction of IL-6 and IL-8 release from respiratory epithelial cells and alveolar macrophages. The results would give an indication to what extent the bacteria contribute to the toxic inflammation following exposure to swine dust. Methods: Epithelial cells from a human lung carcinoma cell line (A549) and human alveolar macrophages obtained from healthy subjects by bronchoalveolar lavage, were stimulated with swine dust, LPS, one Gram negative and four Gram positive bacteria strains. The dose-response release of IL-6 and IL-8 were studied. In addition, a bacteria-free supernatant was prepared from each strain and used for stimulation. Results: With a few exceptions, a dose-dependent IL-6 and IL-8 release was demonstrated from both cell types after stimulation with bacteria. In epithelial cells, Escherichia coli was the most potent bacteria at the highest concentration of 400 bacteria/cell regarding secretion of both IL-6 and IL-8 (P < 0.001), followed by Staphylococcus hominis and Staphylococcus lentus. In alveolar macrophages, S. lentus was the most potent strain (P < 0.001) in inducing cytokine release (P < 0.001), followed by S. hominis and E. coli concerning IL-6 secretion or Micrococcus luteus and E. coli with respect to IL-8 secretion (P < 0.001). Differences in potency between the various bacteria could be demonstrated, both within the two cell types as well as between the epithelial cells and macrophages. Bacteria-free supernatants were also able to induce cytokine release in both cell types. In macrophages the supernatants were even more potent stimuli than whole bacteria. Conclusions: The results indicate that bacteria or bacterial products could be an important contributing factor to the inflammatory reaction following exposure to swine dust.     

周期性应变诱导血管平滑肌细胞桩蛋白和踝蛋白的表达

利用脉动膜式张应力系统,给离体培养的VSMCs施加14%,1 Hz的周期性应变,免疫荧光细胞化学染色,激光共聚焦扫描显微镜观察、分析桩蛋白和踝蛋白的表达变化.结果表明,周期性应变促进VSMCs桩蛋白和踝蛋白的表达增加.说明桩蛋白和踝蛋白是周期性应变条件下VSMCs细胞内信号传递的重要信号物质.     

Pro-Inflammatory Cytokines Induce Expression of Matrix-Metabolizing Enzymes in Human Cervical Smooth Muscle Cells

The process of cervical ripening has been likened to an inflammatory reaction associated with the catabolism of cervical extracellular matrix by enzymes released from infiltrating leukocytes. We hypothesized that smooth muscle cells in the cervix also participate in this process and that pro-inflammatory cytokines act on cervical smooth muscle cells (CSMC) to provoke the expression of matrix-degrading enzymes. We treated primary cultures of human CSMC with tumor necrosis factor-alpha (TNF-alpha) and examined expression of the elastinolytic enzyme, cathepsin S, the collagen metabolizing matrix metalloproteinases (MMP)-1, -3, -9, and the tissue inhibitor of metalloproteinase (TIMP)-1 and -2. A time course analysis revealed that 10 ng/ml of TNF-alpha induced cathepsin S, MMP-1, -3, and -9 mRNA expression with the maximal response observed after 24-48 hours. TNF-alpha induced cathepsin S, MMP-1, -3, and -9 mRNA expression in a dose-dependent manner: the maximal effect was observed at a concentration of 10 ng/ml, with appreciable increases observed at concentrations of 0.1 to 1.0 ng/ml. In contrast, TIMP-1 and -2 mRNAs were not significantly increased by TNF-alpha treatment. Interleukin-1beta produced a pattern of gene expression in the CSMC similar to that observed following TNF-alpha treatment. Western blot analysis and zymography confirmed the induction of proMMP-1, -3, and -9 in response to TNF-alpha, but MMP-2 immunoreactivity and zymographic activity were unaffected. TNF-alpha increased secretion of procathepsin S, but did not affect TIMP-1 and reduced TIMP-2 production. We conclude that CSMC are targets of pro-inflammatory cytokines, which induce a repertoire of enzymes capable of degrading the cervical extracellular matrix. The induction of these enzymes may facilitate the normal ripening of the cervix at term and participate in the premature cervical changes associated with preterm labor.     

Expression of Mn-Superoxide Dismutase Gene in Nontumorigenic and Tumorigenic Human Mammary Epithelial Cells

Manganese superoxide dismutase (Mn-SOD), localizedat the mitochondrial matrix, has the ability to protect cellsagainst oxidative damage. It has been reported that low levels ofMn-SOD gene expression cause the development of certain kind oftumors. On the other hand, overexpression of Mn-SOD gene may playan important role in the development of cancer. In our study, wefind that Mn-SOD activity was higher in nonaggressive (MCF-7) andaggressive (BT-549 and 11-9-14) breast cancer cell lines comparedto that of nontumorigenic (MCF-12A and MCF-12F) mammaryepithelial cell lines. We also observed an increased expressionof Mn-SOD gene in cancerous cell lines. The elevated level of SODactivity in nonaggressive and aggressive breast epithelial celllines was associated with some changes in nucleotide sequence.     

Increased Tie2 Expression, Enhanced Response to Angiopoietin-1, and Dysregulated Angiopoietin-2 Expression in Hemangioma-Derived Endothelial Cells

Infantile hemangiomas are endothelial tumors that grow rapidly in the first year of life and regress slowly during early childhood. Although hemangiomas are well-known vascular lesions, little is known about the mechanisms that cause the excessive endothelial cell proliferation in these most common tumors of infancy. To investigate the molecular basis of hemangioma, we isolated endothelial cells from several proliferative-phase lesions and showed that these cells are clonal and exhibit abnormal properties in vitro (E. Boye, Y. Yu, G. Paranya, J. B. Mulliken, B. R. Olsen, J. Bischoff: Clonality and altered behavior of endothelial cells from hemangiomas. J Clin Invest 2001, 107:745-752). Here, we analyzed mRNA expression patterns of genes required for angiogenesis, including members of the vascular endothelial growth factor (VEGF)/VEGF receptor family and the angiopoietin/Tie family, in hemangioma-derived and normal endothelial cells. KDR, Flt-1, Tie1, Tie2, and angiopoietin-2 (Ang2) were strongly expressed in cultured hemangioma-derived endothelial cells and in hemangioma tissue. In contrast, there was little expression of angiopoietin-1 (Ang1) or VEGF. We found Tie2 mRNA and protein up-regulated with a concomitant increase in cellular responsiveness to Ang1 in most hemangioma-derived endothelial cells. Ang2 mRNA was down-regulated in response to serum in hemangioma-derived endothelial cells, but not in normal endothelial cells, suggesting altered regulation. These findings implicate Tie2 and its ligands Ang1 and Ang2 in the pathogenesis of hemangioma.     

Effects of Fungi and Eosinophils on Mucin Gene Expression in Rhinovirus-Infected Nasal Epithelial Cells

Purpose

Fungi, rhinoviruses (RVs), and eosinophils are associated with upper respiratory diseases. We evaluated the effects of fungal stimulation and eosinophil co-culture on the expression of mucin genes in RV-infected nasal polyp epithelial cells.

Methods

Nasal polyp epithelial cells were obtained from chronic rhinosinusitis patients. Cultured epithelial cells were stimulated with Alternaria and Aspergillus with or without RV-16 infection. The epithelial cells were co-cultured with eosinophils for 16 h. MUC4, MUC5AC, MUC5B, and MUC8 mRNA expressions in the epithelial cells were quantified using real-time RT-PCR. To determine the underlying mechanism, nuclear factor-κB (NF-κB), activator protein-1 (AP-1), and mitogen-activated protein kinase (MAPK) inhibitors were used to inhibit mucin gene expression.

Results

Fungi and RV-16 induced mucin gene expression in nasal polyp epithelial cells. However, there was no synergistic increase in mucin gene expression, with the exception of MUC4 mRNA expression stimulated by 25 µg/mL Aspergillus. When RV-16-infected epithelial cells were stimulated with fungi and then co-cultured with eosinophils, MUC4, MUC5B, and MUC8 mRNA expressions increased. Mucin gene expression was inhibited by NF-κB inhibitors.

Conclusions

RV-16, airborne fungi, and eosinophils may exacerbate the inflammatory process in nasal mucosal diseases by enhancing mucin gene expression.     

Intimin, Tir, and Shiga Toxin 1 Do Not Influence Enteropathogenic Responses to Shiga Toxin-Producing Escherichia coli in Bovine Ligated Intestinal Loops

Shiga toxin-producing Escherchia coli (STEC) comprises a group of attaching and effacing (A/E) enteric pathogens of animals and humans. Natural and experimental infection of calves with STEC may result in acute enteritis or subclinical infection, depending on serotype- and host-specific factors. To quantify intestinal secretory and inflammatory responses to STEC in the bovine intestine, serotypes that are associated with human disease (O103:H2 and O157:H7) were introduced into ligated mid-ileal loops in gnotobiotic and conventional calves, and fluid accumulation and recruitment of radiolabeled neutrophils were measured after 12 h. STEC serotype O103:H2, but not serotype O157:H7, elicited strong enteropathogenic responses. To determine if the inflammatory response to STEC O103:H2 in calves requires Shiga toxin 1 or intimate bacterial attachment to the intestinal epithelium, defined mutations were made in the stx1, eae, and tir genes. Our data indicate that some STEC induce intestinal inflammatory responses in calves by a mechanism that is independent of A/E-lesion formation, intimin, or Shiga toxin 1. This may have implications for strategies to reduce STEC carriage in cattle.     

Selective Up-Regulation of Chemokine IL-8 Expression in Cystic Fibrosis Bronchial Gland Cells in Vivo and in Vitro

Accumulating evidence suggests that the early pulmonary inflammation pathogenesis in cystic fibrosis (CF) may be associated with an abnormal increase in the production of pro-inflammatory cytokines in the CF lung, even in the absence of infectious stimuli. We have postulated that if baseline abnormalities in airway epithelial cell production of cytokines occur in CF, they should be manifested in the CF bronchial submucosal glands, which are known to express high levels of CFTR (cystic fibrosis transmembrane conductance regulator) protein, the gene product mutated in CF disease. Immunohistochemical analyses showed that CF bronchial submucosal glands in patients homozygous for the ΔF508 deletion expressed elevated levels of the endogenous chemokine interleukin (IL)-8 but not the pro-inflammatory cytokines IL-1β and IL-6, compared with non-CF bronchial glands. Moreover, basal protein and mRNA expression of IL-8 were constitutively up-regulated in cultured ΔF508 homozygous CF human bronchial gland cells, in an unstimulated state, compared with non-CF bronchial gland cells. Furthermore, the exposure of CF and non-CF bronchial gland cells to an elevated extracellular Cl⁻ concentration markedly increased the release of IL-8, which can be corrected in CF gland cells by reducing the extracellular Cl⁻ concentration. We also found that, in contrast to non-CF gland cells, dexamethasone did not inhibit the release of IL-8 by cultured CF gland cells. The selective up-regulation of bronchial submucosal gland IL-8 could represent a primary event that initiates early airway submucosal inflammation in CF patients. These findings are relevant to the pathogenesis of CF and suggest a novel pathophysiological concept for the early and sustained airway inflammation in CF patients.     

Macaque Paneth Cells Express Lymphoid Chemokine CXCL13 and Other Antimicrobial Peptides Not Previously Described as Expressed in Intestinal Crypts

CXCL13 is a constitutively expressed chemokine that controls migration of immune cells to lymphoid follicles. Previously, we found CXCL13 mRNA levels increased in rhesus macaque spleen tissues during AIDS. This led us to examine the levels and locations of CXCL13 by detailed in situ methods in cynomolgus macaque lymphoid and intestinal tissues. Our results revealed that there were distinct localization patterns of CXCL13 mRNA compared to protein in germinal centers. These patterns shifted during the course of simian immunodeficiency virus (SIV) infection, with increased mRNA expression within and around follicles during AIDS compared to uninfected or acutely infected animals. Unexpectedly, CXCL13 expression was also found in abundance in Paneth cells in crypts throughout the small intestine. Therefore, we expanded our analyses to include chemokines and antimicrobial peptides (AMPs) not previously demonstrated to be expressed by Paneth cells in intestinal tissues. We examined the expression patterns of multiple chemokines, including CCL25, as well as α-defensin 6 (DEFA6), β-defensin 2 (BDEF2), rhesus θ-defensin 1 (RTD-1), and Reg3γ in situ in intestinal tissues. Of the 10 chemokines examined, CXCL13 was unique in its expression by Paneth cells. BDEF2, RTD-1, and Reg3γ were also expressed by Paneth cells. BDEF2 and RTD-1 previously have not been shown to be expressed by Paneth cells. These findings expand our understanding of mucosal immunology, innate antimicrobial defenses, homeostatic chemokine function, and host protective mechanisms against microbial translocation.     

Increased Systemic Cytokine/Chemokine Expression in Asthmatic and Non‐asthmatic Patients with Bacterial,Viral or Mixed Lung Infection

This study was aimed to determine the profiles of serum cytokines (IL‐1β, TNF‐α, IL‐4, IL‐5) and chemokines (MCP‐1: monocyte chemoattract protein‐1 and RANTES: regulated on activation normal T cell expressed and secreted) in individuals with an asthmatic versus a non‐asthmatic background with bacterial, viral or mixed acute respiratory infection. Asthmatic (n = 14) and non‐asthmatic (n = 29) patients with acute viral, bacterial or mixed (bacterial and viruses) respiratory infection were studied. Patients were also analysed as individuals with pneumonia or bronchitis. Healthy individuals with similar age and sex (n = 10) were used as controls. Cytokine/chemokine content in serum was determined by ELISA. Increased cytokine/chemokine concentration in asthmatic and non‐asthmatic patients was observed. However, higher concentrations of chemokines (MCP‐1 and RANTES) in asthmatic patients infected by viruses, bacteria or bacteria and viruses (mixed) than in non‐asthmatic patients were observed. In general, viral and mixed infections were better cytokine/chemokine inducers than bacterial infection. Cytokine/chemokine expression was similarly increased in both asthmatic and non‐asthmatic patients with pneumonia or bronchitis, except that RANTES remained at normal levels in bronchitis. Circulating cytokine profiles induced by acute viral, bacterial or mixed lung infection were not related to asthmatic background, except for chemokines that were increased in asthmatic status.