IL-4-independent pathways exacerbate methacholine-induced airway hyperreactivity during mycoplasma respiratory disease

BACKGROUND: Mycoplasma respiratory infections are associated with wheezing and exacerbation of airway hyperresponsiveness (AHR) in asthmatic patients. IL-4 is a key cytokine in the development of AHR and airway reconstruction in asthmatic patients and might be an important component in exacerbation of AHR during pulmonary mycoplasma infection. OBJECTIVE: This study evaluates the effect of IL-4 on the severity of methacholine-induced AHR associated with mycoplasma pulmonary mycoplasma infection. METHODS: BALB/c and IL-4 knockout (KO) mice were infected with Mycoplasma pulmonis, and their enhanced pause scores were monitored before and after methacholine inhalation with whole-body plethysmography. RESULTS: IL-4 KO mice showed no difference in histopathology of the lungs before or after Mycoplasma pulmonis infection when compared with BALB/c mice. There was an increase in airway obstruction from days 7 to 21 after infection in both strains of mice, but there was no strain difference in airway resistance-associated mycoplasma disease. However, IL-4 KO mice had significantly higher methacholine-induced AHR after M pulmonis infection when compared with BALB/c mice. There was no difference in AHR between uninfected IL-4 KO and control mice. CONCLUSION: In contrast to our hypothesis, IL-4-independent pathways exacerbate methacholine-induced AHR and promote airway obstruction during the pathogenesis of mycoplasma respiratory disease.     

Dissociation of airway hyperresponsiveness from immunoglobulin E and airway eosinophilia in a murine model of allergic asthma.

Nonspecific airway hyperresponsiveness (AHR) is a hallmark of human asthma. Both airway eosinophilia and high serum levels of total and antigen-specific immunoglobulin E (IgE) are associated with AHR. It is unclear, however, whether either eosinophilia or increased IgE levels contribute directly to, or predict, the development of AHR. Investigations conducted with various murine models of asthma and different mouse strains have resulted in conflicting evidence about the roles that IgE and airway eosinophilia play in the manifestation of AHR. We show that systemic priming with ovalbumin (OVA) in alum, followed by a single day of OVA aerosol challenge, is sufficient to induce AHR, as measured by increased pulmonary resistance in response to intravenously delivered methacholine in BALB/c, but not C57BL/6 or B6D2F1, mice. This was observed despite the fact that OVA-challenged BALB/c mice had less airway eosinophilia and smaller increases in total IgE than either C57BL/6 or B6D2F1 mice, and had less pulmonary inflammation and OVA-specific IgE than B6D2F1 mice. We conclude that airway eosinophilia, pulmonary inflammation, and high serum levels of total or OVA-specific IgE are all insufficient to induce AHR in C57BL/6 and B6D2F1 mice, whereas BALB/c mice demonstrate AHR in the absence of airway eosinophilia. These data confirm that the development of AHR is genetically determined, not only in naive mice, but also in actively immunized ones, and cannot be predicted by levels of airway eosinophilia, pulmonary inflammation, total IgE, or antigen-specific IgE.     

Respiratory tract infection with Mycoplasma pneumoniae in interleukin-12 knockout mice results in improved bacterial clearance and reduced pulmonary inflammation

Mycoplasma pneumoniae is a leading cause of pneumonia and is associated with asthma. Evidence links M. pneumoniae respiratory disease severity with interleukin-12 (IL-12) concentration in respiratory secretions. We evaluated the microbiologic, inflammatory, and pulmonary function indices of M. pneumoniae pneumonia in IL-12 (p35) knockout (KO) mice and wild-type (WT) mice to determine the role of IL-12 in M. pneumoniae respiratory disease. Eight-week-old wild-type BALB/c mice and 8-week-old IL-12 (p35) KO BALB/c mice were inoculated once intranasally with 10(7) CFU of M. pneumoniae. Mice were evaluated at days 2, 4, and 7 after inoculation. Outcome variables included quantitative bronchoalveolar lavage (BAL) M. pneumoniae culture, lung histopathologic scores (HPS), BAL cytokine concentrations determined by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor) and plethysmography, before and after methacholine, to assess airway obstruction (AO) and airway hyperreactivity (AHR). IL-12 (p35) KO mice infected with M. pneumoniae were found to have significantly lower BAL M. pneumoniae concentrations compared with M. pneumoniae-infected WT mice. Lung HPS and the parenchymal pneumonia subscores (neutrophilic alveolar infiltrate), as well as AO, were significantly lower in infected KO mice. No difference was found for AHR. Infected KO mice had significantly lower BAL concentrations of IFN-gamma than WT mice; a trend toward lower BAL concentrations was observed for IL-10 (P = 0.065) and TNF-alpha (P = 0.078). No differences were found for IL-1beta, IL-2, IL-4, IL-5, or IL-6. The lack of IL-12 in experimental M. pneumoniae pneumonia was associated with less severe pulmonary disease and more rapid microbiologic and histologic resolution.     

Genetically determined disparate innate and adaptive cell-mediated immune responses to pulmonary Mycobacterium bovis BCG infection in C57BL/6 and BALB/c mice

The current study was designed to investigate the impact of genetic heterogeneity on host immune responses to pulmonary intracellular infection by using two mouse strains of distinct genetic background, C57BL/6 and BALB/c mice, and a model intracellular pathogen, Mycobacterium bovis BCG. Upon infection, compared to C57BL/6 mice, BALB/c mice developed an earlier response of interleukin 12 (IL-12), gamma interferon (IFN-gamma), tumor necrosis factor alpha, and macrophage chemoattractive protein 1, and greater neutrophilic influx to the lung by days 7 and 14. However, the level of these cytokines at days 27, 43, and 71 was much lower in BALB/c mice than in C57BL/6 mice. The magnitude of cellular responses was also much lower in the lung of BALB/c mice around day 27. Histologically, while C57BL/6 mice developed lymphocytic granulomas, BALB/c mice displayed atypical granulomas in the lung. Of importance, the level of type 2 cytokines IL-4 and IL-10 remained low and similar in the lung of both C57BL/6 and BALB/c mice throughout. Furthermore, lymphocytes isolated from systemic and local lymphoid tissues of infected BALB/c mice demonstrated a markedly lower antigen-specific IFN-gamma recall response. While the number of mycobacterial bacilli recovered from both the lung and spleen of BALB/c mice was similar to that in C57BL/6 mice at day 14, it was higher than that in C57BL/6 mice at day 43. However, it was eventually leveled off to that in C57BL/6 counterparts later. These results suggest the following: (i) genetic heterogeneity can lead to differential innate and adaptive cell-mediated immune responses to primary pulmonary mycobacterial infection; (ii) it is the level of adaptive, but not innate, immune response that is critical to host resistance; and (iii) a lower type 1 immune response in BALB/c mice is not accompanied by a heightened type 2 response during pulmonary mycobacterial infection.     

Susceptibility to Yersinia pseudotuberculosis Infection is Linked to the Pattern of Macrophage Activation

T helper 1 cells play a crucial role in the clearance of Yersinia pseudotuberculosis infection. By producing cytokines and presenting antigens to T cells, activated macrophages can orientate the adaptive immune response. The pathway used by macrophages to metabolize arginine has been employed as an important parameter to discriminate their activation state. In this study, the pattern of macrophage activation in Y. pseudotuberculosis- infected BALB/ c ( Yersinia -susceptible) and C57BL/6 ( Yersinia -resistant) mice and their immunostimulatory capacity were analysed. In the early phase of infection, macrophages obtained from C57BL/6 mice produced higher levels of NO, lower arginase activity, and larger amounts of IL-12 and TNF-α than macrophages from BALB/ c mice. On the other hand, macrophages derived from BALB/ c mice produced higher levels of IL-10 and TGF-β than C57BL/6 mice. The Y. pseudotuberculosis infection leads to a fall in the macrophage immunostimulatory capacity of both strains of mice, with T-cell proliferation significantly reduced 12 h after infection. Moreover, we observed in the supernatant of co-culture of macrophages from infected mice with T lymphocytes from heat-killed Yersinia -immunized mice lower IFN-γ production by cells from BALB/ c mice than by C57BL/6 mice, and IL-4 was produced only by BALB/ c mice on the first- and third-day post-infection. These results suggest that the pattern of macrophage activation is associated with susceptibility and resistance to Y. pseudotuberculosis infection in BALB/ c and C57BL/6 mice.     

Neutrophil depletion exacerbates experimental Chagas' disease in BALB/c, but protects C57BL/6 mice through modulating the Th1/Th2 dichotomy in different directions

To elucidate the roles of neutrophils in experimental Chagas' disease, we depleted the peripheral neutrophils in BALB/c and C57BL/6 mice with a monoclonal antibody 1 day before Trypanosoma cruzi infection. Neutrophil depletion in BALB/ c mice resulted in exacerbation of the disease and decreased expression of mRNA for Th1 cytokines, including IL-2 and IFN-gamma, IL-12p40 and TNF-alpha in their spleens after the infection, while a Th2 cytokine, IL-10, increased especially 1 day after infection. Neutrophils from infected BALB / c mice expressed mRNA for IL-12p40, IFN-gamma, TNF-alpha and Th1 chemoattractive chemokines, monokine induced by IFN-gamma (MIG) and macrophage inflammatory protein-1alpha (MIP-1alpha ). In contrast, in C57BL/6 mice neutrophil depletion induced resistance to the disease and enhanced the expression of the above Th1 cytokines, although IL-10 mRNA in neutrophil-depleted C57BL/6 mice was also higher than in control mice. Neutrophils from C57BL/6 mice did not express IL-12p40, IFN-gamma and MIG but expressed TNF-alpha, MIP-1alpha and IL-10. Therefore, neutrophils may play opposite roles in these two strains of mice with respect to protection versus exacerbation of T. cruzi infection, possibly through modulating the Th1/Th2 dichotomy in different directions.     

Reciprocal immunomodulatory effects of gamma interferon and interleukin-4 on filaria-induced airway hyperresponsiveness

Tropical pulmonary eosinophilia (TPE) is a severe asthmatic syndrome of lymphatic filariasis, in which an allergic response is induced to microfilariae (Mf) in the lungs. Previously, in a murine model for TPE, we have demonstrated that recombinant interleukin-12 (IL-12) suppresses pulmonary eosinophilia and airway hyperresponsiveness (AHR) by modulating the T helper (Th) response in the lungs from Th2- to Th1-like, with elevated gamma-interferon (IFN-gamma) production and decreased IL-4 and IL-5 production. The present study examined the immunomodulatory roles of IL-4 and IFN-gamma in filaria-induced AHR and pulmonary inflammation using mice genetically deficient in these cytokines. C57BL/6, IL-4 gene knockout (IL-4(-/-)), and IFN-gamma(-/-) mice were first immunized with soluble Brugia malayi antigens and then inoculated intravenously with 200,000 live Mf. Compared with C57BL/6 mice, IL-4(-/-) mice exhibited significantly reduced AHR, whereas IFN-gamma(-/-) mice had increased AHR. Histopathologically, each mouse strain showed increased cellular infiltration into the lung parenchyma and bronchoalveolar space compared with na?ve animals. However, consistent with changes in AHR, IL-4(-/-) mice had less inflammation than C57BL/6 mice, whereas IFN-gamma(-/-) mice had exacerbated pulmonary inflammation with the loss of pulmonary architecture. Systemically, IL-4(-/-) mice produced significantly higher IFN-gamma levels compared with C57BL/6 mice, whereas IFN-gamma(-/-) mice produced significantly higher IL-4 levels. These data indicate that IL-4 is required for the induction of filaria-induced AHR, whereas IFN-gamma suppresses AHR.     

TNF can contribute to multiple features of ovalbumin-induced allergic inflammation of the airways in mice

BACKGROUND: TNF is thought to contribute to airway hyperreactivity (AHR) and airway inflammation in asthma. However, studies with TNF-deficient or TNF receptor-deficient mice have not produced a clear picture of the role of TNF in the AHR associated with allergic inflammation in the mouse. OBJECTIVE: We used a genetic approach to investigate the contributions of TNF to antigen-induced AHR and airway inflammation in mice on the C57BL/6 background. METHODS: We analyzed features of airway allergic inflammation, including antigen-induced AHR, in C57BL/6 wild-type and TNF(-/-) mice, using 2 different methods for sensitizing the mice to ovalbumin (OVA). RESULTS: In mice sensitized to OVA administered with the adjuvant aluminum hydroxide (alum), which develop IgE-independent and mast cell-independent allergic inflammation and AHR, we found no significant differences in OVA-induced AHR in C57BL/6-TNF(-/-) versus wild-type mice. By contrast, in mice sensitized to OVA without alum, which develop allergic inflammation that is significantly mast cell-dependent, C57BL/6-TNF(-/-) mice exhibited significant reductions versus wild-type mice in OVA-induced AHR to methacholine; numbers of lymphocytes, neutrophils, and eosinophils in bronchoalveolar lavage fluid; levels of myeloperoxidase, eosinophil peroxidase, and the cytokines IL-4, IL-5, and IL-17 in lung tissue; and histologic evidence of pulmonary inflammation. CONCLUSION: In pulmonary allergic inflammation induced in mice immunized with OVA without alum, TNF significantly contributes to several features of the response, including antigen-induced inflammation and AHR. CLINICAL IMPLICATIONS: Our findings in mice support the hypothesis that TNF can promote the allergic inflammation and AHR associated with asthma.     

Differential CD86 and CD40 co-stimulatory molecules and cytokine expression pattern induced by Trypanosoma cruzi in APCs from resistant or susceptible mice

Differential aspects of the host immune response generated by Trypanosoma cruzi infection were examined in two different mouse strains, BALB/c (haplotype H2-Kd) which does not overcome the acute phase of the infection and C57BL/6 (haplotype H2-Kb) which survives to the acute phase. After infection an increase in CD3+ T cells was observed in both mouse strains in the peritoneal cavity. However, while the CD3+ T cells from the BALB/c mice showed an increase in the IL-4 cytokine expression level, the same type of cells from the C57BL/6 mice showed an increase in IFN-gamma expression. In addition, only the macrophages from the C57BL/6 mice were activated secreting IL-12 and TNF-alpha and producing, moreover, high levels of nitrites. It was observed that also after parasite infection the expression of macrophage and dendritic cells CD40 and CD86 co-stimulation molecules from the spleen were diminished in BALB/c but not in C57BL/6 mice. In correlation with this observation the macrophages from the spleen of infected BALB/c mice secreted lower concentrations of nitrites than the C57BL/6 mouse cells. Also, the spleen dendritic cells from infected BALB/c mice had a small potential to present alloantigens in contrast to that observed in the infected C57BL/6 mouse cells.     

Antibody and cytokine responses to the cilium-associated respiratory bacillus in BALB/c and C57BL/6 mice

The cilium-associated respiratory (CAR) bacillus is a gram-negative, gliding bacterium that causes persistent respiratory tract infections in rodents despite histologic and serologic evidence of a marked immune response. To assess humoral immunity and cytokine responses in CAR bacillus disease, 6-week-old female BALB/c and C57BL/6 mice were inoculated intratracheally with 10(5) CAR bacillus organisms. CAR bacillus-specific serum immunoglobulins (immunoglobulin M [IgM], IgG1, IgG2a, IgG2b, IgG3, and IgA) and local pulmonary cytokines (tumor necrosis factor alpha [TNF-alpha], gamma interferon [IFN-gamma], and interleukin-4 [IL-4]) were evaluated by enzyme-linked immunosorbent assay every 7 days for 49 days. BALB/c mice developed CAR bacillus-induced lesions early in the course of disease that became more severe with time. Correlating with increasing disease severity, BALB/c mice had elevations in all antibody isotypes tested, and elevations in pulmonary TNF-alpha, IFN-gamma, and IL-4. C57BL/6 mice developed mild lesions with mild increases in serum IgM, IgG1, IgG2b, and IgG3 levels and minimally detectable IgG2a and IgA. Cytokine perturbations were not detected in C57BL/6 mice. The persistence of infection in BALB/c mice with vigorous serum antibody responses and increased IFN-gamma and IL-4 responses suggests that humoral immunity and T-cell responses are ineffective at preventing CAR bacillus disease. Furthermore, the lackluster antibody responses and undetectable cytokine responses in C57BL/6 mice suggest that humoral immunity and T-cell responses are not critical in resistance to CAR bacillus-induced disease.     

Expression of heme oxygenase-1 and its effects in allergic airway inflammation and hyperresponsiveness]

We investigated whether an expression of hemeoxygenase-1 (HO-1) within the lung tissue is related to allergic airway inflammation and HO-1 expression could influence airway hyperreactivity (AHR) and eosinophilia in C57BL/6 mice actively sensitized to ovalbumin. The number of HO-1 positive cells was increased in the subepithelium of the bronchi after OVA challenge and HO-1 was localized to alveolar macrophage.Zinc-protoporphyrin (Zn-PP), a competitive inhibitor of hemeoxygenase, by intraperitoneal injection clearly inhibited AHR, pulmonary eosinophilia and IL-5 and IL-13 in the lung tissue. These data indicate that the expression of HO-1 is increased within the lung tissue in allergic airway inflammation and the overexpression of HO-1 could enhanced allergic airway inflammation.     

Macrophage activity in resistant and susceptible mouse strains infected with Mycobacterium lepraemurium.

The level of activation of peritoneal macrophages following subcutaneous inoculation of resistant (C57BL) and susceptible (BALB/c) mice was assessed by monitoring superoxide anion and hydrogen peroxide production and also tumour cell cytostasis. The level of systemic macrophage activation appeared to correlate with bacterial load, rather than resistance to infection. It was observed that the more susceptible (BALB/c) strain developed higher and more sustained levels of systemic macrophage activation, whereas the more resistant (C57BL) strain showed only low transient levels of macrophage activation. In contrast, in vivo challenge of subcutaneously infected C57BL mice, via the intra-peritoneal route, with heat-killed Mycobacterium lepraemurium and thioglycollate resulted in a high level of macrophage activation compared with similarly treated uninfected mice. Similar treatment of susceptible BALB/c mice, however, did not result in enhanced macrophage activation. It was also observed that high levels of macrophage activation occurred in T-cell deprived C57BL mice following infection with M. lepraemurium.     

Elevated cytokine and chemokine levels and prolonged pulmonary airflow resistance in a murine Mycoplasma pneumoniae pneumonia model: a microbiologic, histologic, immunologic, and respiratory plethysmographic profile

Because Mycoplasma pneumoniae is hypothesized to play an important role in reactive airway disease/asthma, a comprehensive murine model of M. pneumoniae lower respiratory infection was established. BALB/c mice were intranasally inoculated once with M. pneumoniae and sacrificed at 0 to 42 days postinoculation. All mice became infected and developed histologic evidence of acute pulmonary inflammation, which cleared by 28 days postinoculation. By contrast, M. pneumoniae persisted in the respiratory tract for the entire 42 days studied. Tumor necrosis factor alpha, gamma interferon, interleukin-6 (IL-6), KC (functional IL-8), MIP-1alpha, and MCP-1/JE concentrations were significantly elevated in bronchoalveolar lavage samples, whereas IL-4 and IL-10 concentrations were not significantly elevated. Pulmonary airflow resistance, as measured by plethysmography, was detected 1 day postinoculation and persisted even after pulmonary inflammation had resolved at day 28. Serum anti-M. pneumoniae immunoglobulin G titers were positive in all mice by 35 days. This mouse model provides a means to investigate the immunopathogenesis of M. pneumoniae infection and its possible role in reactive airway disease/asthma.     

Strain differences influence murine pulmonary responses to Stachybotrys chartarum

When the fungus Stachybotrys chartarum is inhaled, its mycotoxins may cause lung injury and inflammation. The severity of human responses to S. chartarum in both occupational and home settings varies widely. To explore these differences, we intratracheally instilled C3H/HeJ, BALB/c, and C57BL/6J mice with S. chartarum spores suspended in saline. One day later, the mice were humanely killed, bronchoalveolar lavage (BAL) was performed, and biochemical and cellular indicators of lung injury and inflammation were measured. BALB/c mice showed the highest myeloperoxidase activity, albumin and hemoglobin levels, and neutrophil numbers in their BAL among the three strains. BALB/c was the only strain to show significant increases in keratinocyte-derived cytokine (KC), monocyte chemotactic protein (MCP)-1, MCP-3, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, MIP-1gamma, MIP-2, RANTES, IL-1alpha, IL-1beta, IL-3, IL-6, IL-18, leukemia inhibitory factor, macrophage colony-stimulating factor, and TNF-alpha. A model of allergen-induced airway inflammation was examined to assess whether underlying allergic inflammation might contribute to increased susceptibility to S. chartarum-induced pulmonary inflammation and injury. Surprisingly, in BALB/c mice, ovalbumin-induced airway inflammation produced a protective effect against some S. chartarum-induced pulmonary responses. This is the first report of mammalian strain differences affecting responses to S. chartarum. These responses differ from those reported for LPS and other fungi. Analogous underlying genetic differences may contribute to the wide range of sensitivity to Stachybotrys among humans.     

Genetic background affects the expansion of macrophage subsets in the lungs of Mycobacterium tuberculosis‐infected hosts

M1 macrophages are more effective in the induction of the inflammatory response and clearance of Mycobacterium tuberculosis than M2 macrophages. Infected C57BL/6 mice generate a stronger cellular immune response compared with BALB/c mice. We hypothesized that infected C57BL/6 mice would exhibit a higher frequency and function of M1 macrophages than infected BALB/c mice. Our findings show a higher ratio of macrophages to M2 macrophages in the lungs of chronically infected C57BL/6 mice compared with BALB/c mice. However, there was no difference in the functional ability of M1 and M2 macrophages for the two strains in vitro. In vivo, a deleterious role for M2 macrophages was confirmed by M2 cell transfer, which rendered the infected C57BL/6, but not the BALB/c mice, more susceptible and resulted in mild lung inflammation compared with C57BL/6 mice that did not undergo cell transfer. M1 cell transfer induced a higher inflammatory response, although not protective, in infected BALB/c mice compared with their counterparts that did not undergo cell transfer. These findings demonstrate that an inflammation mediated by M1 macrophages may not induce bacterial tolerance because protection depends on the host genetic background, which drives the magnitude of the inflammatory response against M. tuberculosis in the pulmonary microenvironment. The contribution of our findings is that although M1 macrophage is an effector leucocyte with microbicidal machinery, its dominant role depends on the balance of M1 and M2 subsets, which is driven by the host genetic background.     

The role of macrophage activation and of Bcg-encoded macrophage function(s) in the control of Mycobacterium avium infection in mice.

Following the intraperitoneal inoculation of 2.5 x 10(8) colony-forming units of Mycobacterium avium strain ATCC 25291, there was bacillary growth in the liver, spleen and peritoneal cavity of C57BL/6, C57BL/10, DBA/1 and BALB/c mice whereas DBA/2, C3H/He, CBA/Ca and CD-1 mice controlled the infection showing constant or slightly decreasing numbers of viable bacteria in the liver and spleen and effective clearance of the bacilli from the peritoneal cavities. The acquisition of non-specific resistance (NSR) to Listeria monocytogenes during the infection by M. avium was high in C57BL/6, BALB/c and C3H/He mice and negligible in DBA/2 and CD-1 mice. The magnitude of the acquisition of NSR was reduced in T cell-deficient mice and was directly proportional to the dose of the inoculum of M. avium. The production of hydrogen peroxide by phorbol myristate acetate-stimulated peritoneal macrophages of M. avium-infected mice was higher in C57BL/6 and BALB/c mice than in CD-1, DBA/2 and C3H/He animals. BALB/c. Bcgr (C.D2) mice, unlike their congenic strain BALB/c, restricted bacterial growth following the intravenous inoculation of 2.5 x 10(8) CFU of M. avium as efficiently as DBA/2 mice. C.D2 and BALB/c peritoneal macrophages from infected mice produced similar amounts of H2O2 but BALB/c mice developed higher levels of NSR to listeria than C.D2 mice. The production of nitrite by peritoneal macrophages from infected mice was found to be enhanced in DBA/2 and C3H/He but not in BALB/c, C57BL/6, DC-1 and C.D2 mice. Resident peritoneal macrophages from C.D2 mice were more bacteriostatic in vitro for M. avium than macrophages from BALB/c mice. The same relative differences between the two macrophage populations were observed when the cells were activated with lymphokines. The results show that the populations were observed when the cells were activated with lymphokines. The results show that the resistance to M. avium infection in mice is under the control of the Bcg gene and that susceptibility may be due to some defect in macrophage antibacterial function not completely overcome by the activation of this phagocyte in the susceptible strains of mice.     

Antigen dose defines T helper 1 and T helper 2 responses in the lungs of C57BL/6 and BALB/c mice independently of splenic responses

To investigate the effect of antigen dose on immune response, C57BL/6 and BALB/c mice were sensitized with aluminum hydroxide gel (alum)-precipitated ovalbumin (OVA) then challenged with aerosolized OVA. Low-dose sensitization (less than 8 microg of OVA) elicited T helper 2 (Th2)-type immunoglobulins (Igs) secretion from C57BL/6 mice, including high levels of serum IgE, IgG1 and low levels of IgG2a, while BALB/c mice secreted T helper 1 (Th1)-type Igs, including low levels of IgE, IgG1 and high levels of IgG2a. In contrast, high-dose sensitization (more than 50 microgram) elicited Th1-type Igs secretion in C57BL/6mice, while BALB/c mice exhibited Th2-type Igs secretion. Furthermore, the number of eosinophils infiltrating into the lungs of low-dose OVA-sensitized C57BL/6 mice was significantly greater than in BALB/c mice sensitized with the same amount of OVA. Only a very high dose of OVA (1 mg) could induce greater eosinophil infiltration into the lungs of BALB/c mice compared with C57BL/6 mice. Additionally, low-dose sensitization generated Th2-type cytokines, including high levels of interleukin (IL) -4, IL-5 and a low level of interferon-gamma (IFN-gamma) in the lungs of C57BL/6 mice, while BALB/c mice generated Th1-type cytokines in their lungs, including low levels of IL-4, IL-5 and a high level of IFN-gamma. In contrast, high-dose sensitization elicited Th1-type cytokines production in the lungs of C57BL/6 mice, while BALB/c mice generated Th2-type cytokines in their lungs. Interestingly, splenocyte cultures from C57BL/6 mice produced Th1-type cytokines, while cultures from BALB/c mice produced Th2-type cytokines regardless of OVA sensitization dose (100 ng-1 mg). These results indicate that C57BL/6 and BALB/c mice have different susceptibilities to OVA-sensitization and OVA-induced pulmonary eosinophilia regulated by Th1- and Th2-type cytokines, independent of splenic Th1- and Th2-type cytokines production.     

Differences in innate immune responses correlate with differences in murine susceptibility to Chlamydia muridarum pulmonary infection

We investigated the phenotypic basis for genetically determined differences in susceptibility and resistance to Chlamydia muridarum pulmonary infection using BALB/c and C57BL/6 mice. Following C. muridarum intranasal inoculation, the intensity of infection was very different between BALB/c and C57BL/6 beginning as early as 3 days post‐infection. Intrapulmonary cytokine patterns also differed at early time‐points (days 2 and 4) between these two strains of mice. The early recruitment of neutrophils to lung tissue was greater in BALB/c than in C57BL/6 mice and correlated with a higher number of inclusion forming units (IFU) of C. muridarum. At day 12 post‐infection, BALB/c mice continued to demonstrate a greater burden of infection, significantly higher lung cytokine levels for tumour necrosis factor‐α and interleukin‐17 (IL‐17) and a significantly lower level for interferon‐γ than did C57BL/6 mice. In vitro, bone‐marrow‐derived dendritic cells (BMDCs) from BALB/c mice underwent less functional maturation in response to C. muridarum infection than did BMDCs from C57BL/6 mice. The BMDCs of BALB/c mice expressed lower levels of activation markers (CD80, CD86, CD40 and major histocompatibility complex class II) and secreted less IL‐12 and more IL‐23 than BMDCs from C57BL/6 mice. Overall, the data demonstrate that the differences exhibited by BALB/c and C57BL/6 mice following C. muridarum pulmonary infection are associated with differences in early innate cytokine and cellular responses that are correlated with late differences in T helper type 17 versus type 1 adaptive immune responses.     

Differences in expression of toll-like receptors and their reactivities in dendritic cells in BALB/c and C57BL/6 mice

We have previously reported that differences in early production of interleukin 12 (IL-12) by dendritic cells (DC) underlies the difference between the susceptibilities to Listeria monocytogenes of C57BL/6 and BALB/c mice. To elucidate mechanisms for the different abilities of DC to produce cytokine in C57BL/6 and BALB/c mice, we examined Toll-like receptor (TLR) expression by DC and their responses in vitro to known microbial ligands for TLRs. We found that DC isolated from the spleens of naive C57BL/6 mice preferentially expressed TLR9 mRNA, whereas DC from naive BALB/c mice strongly expressed TLR2, -4, -5, and -6 mRNAs. C57BL/6 DC produced a higher level of IL-12p40 in response to the ligands for TLR4 (lipopolysaccharide), TLR2 (lipoprotein), and TLR9 (CpG), whereas BALB/c DC responded to these ligands by producing a larger amount of monocyte chemoattractant protein 1. C57BL/6 DC expressed higher levels of CD40 and Stat4 than BALB/c DC did, suggesting that naive C57BL/6 mice contained more-mature subsets of DC than naive BALB/c mice. Differences in reactivities of DC to microbial molecules through TLRs may be associated with susceptibility and resistance to Listeria infection in BALB/c and C57BL/6 mice.