Plasma levels of proteins of the alternative complement pathway in inbred mice that differ in resistance to Trypanosoma congolense infections.

Inbred BALB/c, A/J, and C57B1/6J mice were infected with Trypanosoma congolense (Trans Mara strain), clone TC13, and monitored for parasitemia, survival times, and plasma levels of complement components C3, C5, factor B, and factor H. Parasitemia was highest in BALB/c, intermediate in A/J, and lowest in C57Bl/6J mice. The mean survival times were 11.5 +/- 0.9, 23.8 +/- 2.3, and 119 +/- 26 days for BALB/c, A/J, and C57Bl/6J mice, respectively. Preinfection levels of factor H were significantly correlated with survival times (r = 0.7722, P less than 0.001). Marked differences were observed between the plasma levels of C3, factor B, and factor H in the 3 mouse strains following infection. Complement C5 levels showed the fewest changes. In the initial postinfection period, BALB/c mice had highest increases in the levels of the 4 complement proteins but also had the greatest declines toward the end of the infection. Factor H levels showed a biphasic increase in BALB/c and C57Bl/6J, but not in A/J mice, with peaks at days 3 and 9. Complement C3 levels declined in all mice toward the terminal stage of the disease. In the late stages of infection, factor B levels markedly decreased in BALB/c but significantly increased in C57Bl/6J mice. Factor B levels measured at the terminal stages in BALB/c, A/J, and C57Bl/6J were correlated positively with their respective survival times (r = 0.714, P less than 0.01). The results suggest that genetic differences in the alternative complement pathway might affect the resistance to T. congolense infections.     

Innate resistance to experimental African trypanosomiasis: differences in cytokine (TNF-alpha, IL-6, IL-10 and IL-12) production by bone marrow-derived macrophages from resistant and susceptible mice

Resistance to African trypanosomiasis is under multigenic control. BALB/c mice are highly susceptible while C57Bl/6 mice are relatively resistant. Macrophages eliminate opsonized trypanosomes from the bloodstream and are involved in immunosuppression. We therefore investigated the production of a number of cytokines (IL-10, IL-6, TNF-alpha and IL-12) by bone marrow-derived macrophages (BMDM) from C57Bl/6 and BALB/c mice following challenge with either Trypanosoma congolense or Trypanosoma brucei. BMDM from C57Bl/6 mice, upon challenge with whole cell extracts (WCE) of T. congolense or T. brucei, produced significantly more TNF-alpha and IL-12 than those from BALB/c mice. The production of these cytokines was significantly enhanced by pretreatment of the cells with IFN-gamma. BMDM from BALB/c mice, however, produced significantly more IL-6 and IL-10 than those from C57Bl/6 mice. In contrast to LPS stimulation, simultaneous treatment of cells with WCE and IFN-gamma enhanced IL-10 synthesis by BMDM from BALB/c mice. These results indicate that cytokine genes are differentially regulated in macrophages from trypanosome-susceptible and -resistant mice and are consistent with our previous findings wherein retrovirus-immortalized macrophage cell lines from BALB/c and C57Bl/6 mice produce differential amounts of cytokines after phagocytosis of trypanosomes.     

Vascular extracellular adenosine metabolism in mice correlates with susceptibility to atherosclerosis

Abstract

Animal models are widely used in atherosclerosis research. The most useful, economic and valid is mouse genetic model of this pathology. Purinergic signaling is an important mechanism regulating processes involved in the vascular inflammation and atherosclerosis. The aim of this study was to measure vascular activities of nucleotide and adenosine-degrading ecto-enzymes in different strains of mice and to compare them to atherosclerotic susceptibility.

The vascular extracellular nucleotide catabolism pathway was analyzed in 6-month-old male genetically unmodified mouse strains: FVB/NJ, DBA/2J, BALB/c, C57Bl/6J and mouse knock-outs on C57Bl/6J background for LDLR (LDLR-/-) and for ApoE and LDLR (ApoE-/-LDLR-/-). LDLR-/- mice were a model of moderate hypercholesterolemia, while ApoE-/-LDLR-/- mice, a model of severe hypercholesterolemia with advanced atherosclerosis.

FVB/NJ, DBA/2J and BALB/c mice showed high rates of vascular extracellular AMP hydrolysis and low activity of adenosine deamination. In turn, all mice with the C57Bl/6J background expressed diminished activity of vascular AMP hydrolysis. Mice with genetically-induced hyperlipidemia and atherosclerosis on the C57Bl/6J background revealed increased ecto-adenosine deaminase activity.

Mouse strains that were resistant to atherosclerosis (FVB/NJ, DBA/2J, BALB/c) exhibited a protective extracellular vascular ecto-enzyme pattern directed toward the production of anti-inflammatory and anti-atherosclerotic adenosine. In turn, mice with genetically induced hypercholesterolemia and atherosclerosis expressed disturbed activities of ecto-5’nucleotidase and ecto-adenosine deaminase related to decreased production and increased degradation of extracellular adenosine.     

Lack of signaling by IL-4 or by IL-4/IL-13 has more attenuating effects on Leishmania amazonensis dorsal skin--than on footpad-infected mice

Lesion development in tegumentary leishmaniasis is markedly influenced by the inoculation site and the type and number of injected infective forms. This and the yet unclear contribution of Th2 cytokines as susceptibility factors to Leishmania amazonensis infection prompted us to investigate the roles of IL-4, IL-13 and IL-10 on C57BL/6 and BALB/c mice infected in the footpad (paw) or rump with low-dose L. amazonensis purified-metacyclics. Wild-type (WT) mice of either strain developed, in the rump, a single large ulcerated lesion whereas paw lesions never ulcerated and were much smaller in C57BL/6 than in BALB/c mice. However, rump-inoculated IL-4-deficient (IL-4(-/-)) C57BL/6 mice did not develop any visible lesions although parasites remained in the dermis and lymph nodes, even after systemic IL-10-receptor blocking. By comparison, all IL-4(-/-) BALB/c mice developed rump ulcers. Strikingly, only 30% of rump-infected IL-4Rα(-/-) BALB/c mice developed lesions. IL-4(-/-) mice had higher IFN-γ and lower IL-10 and IL-13 levels than WT mice. Paw-infected IL-4Rα(-/-) BALB/c mice developed minimal paw lesions. While other factors contributing to L. amazonensis susceptibility cannot be discounted, our results indicate that absent signalling by IL-4 or by IL-4/IL-13 have more intense attenuating effects on rump than on paw lesions but do not eradicate parasitism.     

Onchocerca volvulus keratitis (river blindness) is exacerbated in BALB/c IL-4 gene knockout mice

To determine the outcome of Onchocerca volvulus keratitis in IL-4(-/-) BALB/c mice, animals were immunized subcutaneously and injected into the corneal stroma with soluble O. volvulus antigens. IL-4(-/-) BALB/c mice had a deviated cellular response, with decreased serum IgE and IgG1 and elevated IgG2a compared with control BALB/c mice. In marked contrast to control BALB/c, C57BL/6, and IL-4(-/-) C57BL/6 mice, IL-4(-/-) BALB/c mice developed severe corneal opacification and neovascularization that was associated with a pronounced neutrophil infiltrate to the corneal stroma. STAT-6(-/-) BALB/c mice had the same phenotype as IL-4(-/-) BALB/c mice, and complement depletion had no effect on the severity of O. volvulus keratitis in these mice. These findings indicate that on a BALB/c background, IL-4 has a critical role in regulating neutrophil recruitment to the cornea and development of O. volvulus keratitis.     

The role of RAGE in the pathogenesis of intestinal barrier dysfunction after hemorrhagic shock

The receptor for advanced glycation end products (RAGE) has been implicated in the pathogenesis of numerous conditions associated with excessive inflammation. To determine whether RAGE-dependent signaling is important in the development of intestinal barrier dysfunction after hemorrhagic shock and resuscitation (HS/R), C57Bl/6, rage(-/-), or congenic rage(+/+) mice were subjected to HS/R (mean arterial pressure of 25 mmHg for 3 h) or a sham procedure. Twenty-four hours later, bacterial translocation to mesenteric lymph nodes and ileal mucosal permeability to FITC-labeled dextran were assessed. Additionally, samples of ileum were obtained for immunofluorescence microscopy, and plasma was collected for measuring IL-6 and IL-10 levels. HS/R in C57Bl/6 mice was associated with increased bacterial translocation, ileal mucosal hyperpermeability, and high circulating levels of IL-6. All of these effects were prevented when C57Bl/6 mice were treated with recombinant human soluble RAGE (sRAGE; the extracellular ligand-binding domain of RAGE). HS/R induced bacterial translocation, ileal mucosal hyperpermeability, and high plasma IL-6 levels in rage(+/+) but not rage(-/-) mice. Circulating IL-10 levels were higher in rage(-/-) compared with rage(+/+) mice. These results suggest that activation of RAGE-dependent signaling is a key factor leading to gut mucosal barrier dysfunction after HS/R.     

The Pro-451 to Leu polymorphism within the C-terminal tail of P2X7 receptor impairs cell death but not phospholipase D activation in murine thymocytes

The P2X family of ATP receptors (P2XR) are ligandgated channels that have been proposed to regulate cell death of immature thymocytes. However, the nature of the P2XR subtype involved has been controversial until recently. In agreement with previous studies, we found that extracellular ATP (ATPe) induces a caspase-dependent apoptosis of BALB/c thymocytes, as observed by DNA fragmentation. Additionally, ATPe induces a predominant caspase-independent thymocytes lysis characterized by plasma membrane disruption. Both responses to ATPe can be induced by a potent P2X7R agonist, benzoylbenzoyl-ATP, whereas P2X7R antagonists, oxidized ATP and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid, inhibited the effect of ATPe. These results are further supported by observations where disruption of the P2X7R gene (P2X7R(-/-) mice) completely abolishes thymocytes death induced by ATPe. Interestingly, the natural P451L mutation in the C-terminal tail of P2X7R present in C57BL/6 mice, which impairs ATPe-dependent pore formation in T lymphocytes, significantly reduces thymocytes death triggered by ATPe. Furthermore, we found that P2X7R from BW5147 thymoma cells also harbors this point mutation, accounting for their insensitivity to ATPe-induced cell death. Concentrations of ATPe effective in inducing cell death also increase phosphatidylcholine-hydrolyzing phospholipase D (PC-PLD) activity in BALB/c thymocytes through the stimulation of P2X7R. However, in contrast to ATPe-induced cell death, PC-PLD activation is totally Ca(2+)-dependent. Moreover, the stimulation of PC-PLD by ATPe is not affected by the P451L mutation present in C57BL/6 thymocytes and BW5147 cells, suggesting that cell death and PC-PLD activity are regulated through distinct domains of the P2X7R. Finally, the inhibition of ATPe-induced PC-PLD stimulation does not affect thymocytes death. Altogether, these data suggest that P2X7R-induced thymocytes death is independent of the stimulation of PC-PLD activity.     

Role of the immune response in Sindbis virus-induced paralysis of SJL/J mice

The pathologic role of the specific immune and inflammatory responses to viral infections of the CNS was investigated by using mice which are susceptible (SJL/J) and resistant (C57Bl6 and BALB/c) to the development of experimental autoimmune encephalomyelitis (EAE). Intracerebral inoculation of 10(4) PFU of Sindbis virus (SV) into 6- to 8-wk-old SJL/J mice resulted in a severe and sometimes fatal encephalomyelitis. A mild to severe hind leg paralysis was observed around days 6 to 7 postinfection (pi) which closely resembled EAE stages and persisted for up to 8 wk pi. Immunosuppression with cyclophosphamide on day 4 alleviated the severity of this disease. Significant perivascular and parenchymal infiltration was present in the brains and spinal cords of SV-infected SJL/J mice for up to 1 mo. This apparent immunopathologic reaction was found to be a characteristic of SJL/J mice, because infection of 6- to 8-wk-old BALB/c and C57Bl6 mice with SV did not cause paralytic disease. These mice also exhibited a significantly milder cellular infiltrate which was mostly resolved on day 12 to 14 pi. Titers of virus in the brain and spinal cords of mice were comparable with clearance by day 7 pi. SV-specific lymphoproliferation and serum antibody responses were also comparable in all mice. SV-infected SJL/J mice developed antibodies to myelin components as demonstrated in Western blots and responded to myelin basic protein by lymphoproliferation. Lymph node cells from these mice, after in vitro challenge with myelin basic protein, transferred a mild EAE-like disease to naive recipients and potentiated subclinical EAE into a severe disease.     

T Cell receptor clonotype influences epitope hierarchy in the CD8+ T cell response to respiratory syncytial virus infection

CD8+ T cell responses are important for recognizing and resolving viral infections. To better understand the selection and hierarchy of virus-specific T cell responses, we compared the T cell receptor (TCR) clonotype in parent and hybrid strains of respiratory syncytial virus-infected mice. K(d)M2(82-90) (SYIGSINNI) in BALB/c and D(b)M(187-195) (NAITNAKII) in C57Bl/6 are both dominant epitopes in parent strains but assume a distinct hierarchy, with K(d)M2(82-90) dominant to D(b)M(187-195) in hybrid CB6F1/J mice. The dominant K(d)M2(82-90) response is relatively public and is restricted primarily to the highly prevalent Vβ13.2 in BALB/c and hybrid mice, whereas D(b)M(187-195) responses in C57BL/6 mice are relatively private and involve multiple Vβ subtypes, some of which are lost in hybrids. A significant frequency of TCR CDR3 sequences in the D(b)M(187-195) response have a distinct "(D/E)WG" motif formed by a limited number of recombination strategies. Modeling of the dominant epitope suggested a flat, featureless structure, but D(b)M(187-195) showed a distinctive structure formed by Lys(7). The data suggest that common recombination events in prevalent Vβ genes may provide a numerical advantage in the T cell response and that distinct epitope structures may impose more limited options for successful TCR selection. Defining how epitope structure is interpreted to inform T cell function will improve the design of future gene-based vaccines.     

B cell response during infection with the MAT a and MAT alpha mating types of Cryptococcus neoformans

In the present study, we compared the B cell response of BALB/c and C57Bl/6 mice during Cryptococcus neoformans infection. This response was investigated using virulent serotype D forms of mating types alpha and a (MAT alpha and MAT a). C57Bl/6 mice showed massive (mainly cerebral) infection by both types, while BALB/c were resistant to infection. Some resistance of C57Bl/6 mice was induced by previous immunization with the capsular polysaccharide from MAT alpha. Passive immunization of C57Bl/6 mice with purified antibody (Ab) obtained from capsular polysaccharide-immunized mice also increased resistance to infection. Both mouse strains showed comparable low IgM response to the capsular polysaccharide from MAT alpha, and only C57Bl/6 mice produced IgM to the polysaccharide of MAT a. Comparable levels of different immunoglobulin (Ig) isotypes against capsular components of MAT alpha and MAT a were detected, and the response of C57Bl/6 mice was higher when compared to that of BALB/c mice. FACS analysis indicated an increase in the percentage of a high-granulosity (side-scatter) splenic subpopulation and in the percentage of splenic Gr-1+ cells in infected C57Bl/6 mice. In addition, the percentage of follicular splenic B cells was decreased after C. neoformans infection of C57Bl/6 mice. This response was more pronounced when we investigated infection induced by the MAT a mating type. Taken together, our results indicate that capsular polysaccharide derived from MAT alpha and MAT a types of C. neoformans have a stimulatory effect upon B cells but that there is no correlation between resistance of BALB/c mice and Ab production. However, the increase in resistance of C57Bl/6 mice parallels the production of Abs and a major change in splenic cell populations.     

Invariant NKT cell defects in vitamin D receptor knockout mice prevents experimental lung inflammation

Vitamin D receptor (VDR) deficiency (knockout [KO]) results in a failure of mice to generate an airway hyperreactivity (AHR) response on both the BALB/c and C57BL/6 background. The cause of the failed AHR response is the defective population of invariant NKT (iNKT) cells in the VDR KO mice because wild-type (WT) iNKT cells rescued the AHR response. VDR KO mice had significantly fewer iNKT cells and normal numbers of T cells in the spleen compared with WT mice. In BALB/c VDR KO mice, the reduced frequencies of iNKT cells were not apparent in the liver or thymus. VDR KO and WT Th2 cells produced similar levels of IFN-γ and IL-5. On the BALB/c background, Th2 cells from VDR KO mice produced less IL-13, whereas on the C57BL/6 background, Th2 cells from VDR KO mice produced less IL-4. Conversely, VDR KO iNKT cells were defective for the production of multiple cytokines (BALB/c: IL-4, IL-5, and IL-13; C57BL/6: IL-4 and IL-17). Despite relatively normal Th2 responses, BALB/c and C57BL/6 VDR KO mice failed to develop AHR responses. The defect in iNKT cells as a result of the VDR KO was more important than the highly susceptible Th2 background of the BALB/c mice. Defective iNKT cell responses in the absence of the VDR result in the failure to generate AHR responses in the lung. The implication of these mechanistic findings for human asthma requires further investigation.     

Analysis of the specific 3H-diazepam binding in the brain of inbred mice with differing emotionality

The influence of sodium chloride and gamma-aminobutyric acid (GABA) on H3-diazepam binding in CNS membrane fraction were investigated in C57Bl/6, BALB/c mice and their F1 hybrids. The addition of GABA (1, 10 and 100 microM) elevated the level of radioligand binding with CNS membranes in all the inbred mice in similar manner. The higher stimulating effect of sodium chloride (50, 100 and 150 mM) on the H3-diazepam reception was found in BALB/c mice and F1 hybrids, as compared to C57Bl/6 mice. It has been suggested that membrane-dependent conformational reconstructions of supramolecular receptor complex are the cause of genetic differences in the regulation of H3-diazepam reception by Cl(-)-ionophore.     

Local inflammation,lethality and cytokine release in mice injected with Bothrops atrox venom.

We have provided evidence that: (a) lethality of mice to crude Bothrops venom varies according the isogenic strain (A/J > C57Bl/6 > A/Sn > BALB/c > C3H/HePas > DBA/2 > C3H/He); (b)BALB/c mice (LD50=100.0 microg) were injected i.p. with 50 microg of venom produced IL-6, IL-10, INF-gamma, TNF-alpha and NO in the serum. In vitro the cells from the mice injected and challenged with the venom only released IL-10 while peritoneal macrophages released IL-10, INF-gamma and less amounts of IL-6; (c) establishment of local inflammation and necrosis induced by the venom, coincides with the peaks of TNF-alpha, IFN-gamma and NO and the damage was neutralized when the venom was incubated with a monoclonal antibody against a 60 kDa haemorrhagic factor. These results suggest that susceptibility to Bothrops atrox venom is genetically dependent but MHC independent; that IL-6, IL-10, TNF-alpha, IFN-gamma and NO can be involved in the mediation of tissue damage; and that the major venom component inducers of the lesions are haemorrhagins.     

Lack of a Functioning P2X7 Receptor Leads to Increased Susceptibility to Toxoplasmic Ileitis

Background

Oral infection of C57BL/6J mice with the protozoan parasite Toxoplasma gondii leads to a lethal inflammatory ileitis.

Principal Findings

Mice lacking the purinergic receptor P2X7R are acutely susceptible to toxoplasmic ileitis, losing significantly more weight than C57BL/6J mice and exhibiting much greater intestinal inflammatory pathology in response to infection with only 10 cysts of T. gondii. This susceptibility is not dependent on the ability of P2X7R-deficient mice to control the parasite, which they accomplish just as efficiently as C57BL/6J mice. Rather, susceptibility is associated with elevated ileal concentrations of pro-inflammatory cytokines, reactive nitrogen intermediates and altered regulation of elements of NFκB activation in P2X7R-deficient mice.

Conclusions

Our data support the thesis that P2X7R, a well-documented activator of pro-inflammatory cytokine production, also plays an important role in the regulation of intestinal inflammation.     

Choice of Mouse Strain Influences the Outcome in a Mouse Model of Chemical-Induced Asthma

Background

The development of occupational asthma is the result of interactions between environmental factors and individual susceptibility. We assessed how our model of chemical-induced asthma is influenced by using different mouse strains.

Methodology/Principal Findings

On days 1 and 8, male mice of 7 different strains (BALB/c, BP/2, A/J, C57Bl/6, DBA/2, CBA and AKR) were dermally treated with toluene-2,4-diisocyanate (TDI) (0.3%) or vehicle (acetone/olive oil, AOO, 2∶3) on each ear (20 µl). On day 15, they received an oropharyngeal instillation of TDI (0.01%) or AOO (1∶4). Airway reactivity to methacholine, total and differential cell counts in bronchoalveolar lavage (BAL) and total serum IgE and IgG_2a levels were measured. Lymphocyte subpopulations in auricular lymph nodes and in vitro release of cytokines by ConA stimulated lymphocytes were assessed. In TDI-sensitized and challenged mice, airway hyper-reactivity was only observed in BALB/c, BP/2, A/J and AKR mice; airway inflammation was most pronounced in BALB/c mice; numbers of T-helper (CD4⁺), T-activated (CD4⁺CD25⁺), T-cytotoxic (CD8⁺) and B- lymphocytes (CD19⁺) were increased in the auricular lymph nodes of BALB/c, BP/2, A/J and CBA mice; elevated concentrations of IL-4, IL-10, IL-13 and IFN-γ were detected in supernatant of lymphocytes from BALB/c, BP/2, A/J, C57Bl/6 and CBA mice cultured with concanavaline A, along with an increase in total serum IgE.

Conclusion

The used mouse strain has considerable and variable impacts on different aspects of the asthma phenotype. The human phenotypical characteristics of chemically-induced occupational asthma were best reproduced in Th2-biased mice and in particular in BALB/c mice.     

Helicobacter pylori-induced mucosal inflammation is Th1 mediated and exacerbated in IL-4, but not IFN-gamma, gene-deficient mice

To elucidate the pathogenesis of Helicobacter pylori-associated gastritis, we studied immune responses of C57BL/6J wild-type (WT), SCID, and gene deficient (IFN-gamma-/- and IL-4-/-) mice following infection with a pathogenic isolate of H. pylori (SPM326). During early infection in WT mice, mononuclear and polymorphonuclear cells accumulated in the gastric lamina propria, and the numbers of cells in the inflamed mucosa expressing IFN-gamma, but not IL-4, mRNA rose significantly (p < 0.005), consistent with a local Th1 response. Splenic T cells from the same infected WT mice produced high levels of IFN-gamma, no detectable IL-4, and low amounts of IL-10 following in vitro H. pylori urease stimulation, reflecting a systemic Th1 response. Infected C57BL/6J SCID mice did not develop gastric inflammation despite colonization by many bacteria. Infected C57BL/10J and BALB/c mice also did not develop gastric inflammation and displayed a mixed Th1/Th2 splenic cytokine profile. These data imply a major role for the Th1 cytokine IFN-gamma in H. pylori-associated gastric inflammation in C57BL/6J mice. Compared with WT animals, infected IL-4-/- animals had more severe gastritis and higher levels of IFN-gamma production by urease-stimulated splenocytes (p < 0.01), whereas IFN-gamma-/- mice exhibited no gastric inflammation and higher levels of IL-4 production by stimulated splenocytes. These findings establish C57BL/6J mice as an important model for H. pylori infection and demonstrate that up-regulated production of IFN-gamma, in the absence of the opposing effects of IL-4 (and possibly IL-10), plays a pivotal role in promoting H. pylori-induced mucosal inflammation.     

A new erythrocytic antigen of C57BL/10 (B10) mice

A new antigen, detectable on murine erythrocytes by hemagglutination assay with a (BALB/cCrl X SWR/J)F1 anti-B10.D2n/Sn alloantiserum, is described. Among the inbred and congenic mouse strains tested for reactivity with the antiserum, only the immunizing strain, B10.D2, and its congenic resistant partner, C57BL/10 (B10), reacted. Three other C57 strains, C57BL/6J, C57BL/6By, and C57L, were negative for the antigen. F1 hybrids between B10 and BALB/c, an antigen-negative strain, were positive for the antigen indicating that its expression is dominant. Typing of 39 (BALB/c X (BALB/c X B10)F1) and 62 [BALB/c X B10)F1 X BALB/c) backcross mice revealed that a single gene controls expression of the antigen. The gene is autosomal and not linked to H-2, Ly-4, or the c (albino) or b coat color genes.     

T cells from Leishmania major-susceptible BALB/c mice have a defect in efficiently up-regulating CXCR3 upon activation

Genetic background influences the outcome of Leishmania major infection. C57BL/6 mice mount a Th1 response and resolve infection. In contrast, BALB/c mice mount a Th2 response and develop chronic lesions. This susceptible phenotype is seen even though BALB/c mice generate IFN-gamma-producing T cells at proportions similar to C57BL/6 mice in their lymph nodes (LN) early after infection. We had previously shown that chemokine receptor CXCR3 mediates immunity against L. major by recruiting IFN-gamma-producing T cells to the lesions of C57BL/6 mice. Therefore, we hypothesized that IFN-gamma-secreting T cells in BALB/c mice are unable to confer protection because they may be defective in up-regulating CXCR3. To test this hypothesis, we analyzed kinetics of CXCR3-expressing T cells in the LN and lesions of BALB/c and C57BL/6 mice during L. major infection. Additionally, we compared the ability of T cells from BALB/c and C57BL/6 mice to up-regulate CXCR3 upon activation. We found that resolution of L. major infection in C57BL/6 mice was associated with an increase in the proportion of CXCR3(+) T cells in regional LN and lesions, whereas disease progression in BALB/c mice was associated with a decrease in these populations. Anti-CD3/CD28-activated T cells from naive BALB/c but not C57BL/6 mice were defective in up-regulating CXCR3. Impaired induction of CXCR3 on BALB/c T cells was not due to lack of IFN-gamma and was mediated partially by IL-10 but not IL-4 or IL-13. We propose that defective CXCR3 up-regulation on T cells in BALB/c mice may contribute to L. major susceptibility.     

A Staphylococcus aureus mouse keratitis topical infection model: cytokine balance in different strains of mice

Staphylococcus is a leading cause of the potentially blinding disease microbial keratitis. Even with the use of antibiotic therapy, the host inflammatory response continues to damage the cornea, which may lead to blindness. Manipulation of the host response may help improve patient outcome from this devastating disease. We aim to understand the contribution of the host response to Staphylococcus aureus infection. A S. aureus keratitis mouse model was developed in both C57BL/6 and BALB/c mice using two different strains of S. aureus (8325-4 and Staph 38). Twenty-four hours postinfection, mice were killed and eyes were harvested for enumeration of bacteria, polymorphonuclear leucocytes, chemokines and cytokines. The laboratory strain 8325-4 was not as virulent as the clinical isolate Staph 38. In vitro data showed a 250-fold increase in invasion of human corneal epithelial cells by Staph 38 compared to 8325-4. BALB/c mice were susceptible to S. aureus infection whereas C57BL/6 mice were resistant. The resistant C57BL/6 mice were polarized towards a Th2 response, which may be protective for these mice. IL-4, IL-10 and IL-6 were elevated significantly in C57BL/6 mice infected with Staph 38 (P < 0.05). Macrophage inflammatory peptide (MIP)-2 was also significantly elevated in C57BL/6 mice (P < 0.001). The susceptible BALB/c mice had a muted cytokine response, which suggests that S. aureus might be 'walled off' during infection and might avoid host defences. IL-4, IL-10 and IL-6 cytokines may be protective during Gram-positive corneal infection and therefore may be useful for adjunct therapies in the treatment of this disease.