Susceptible Mouse Strains Research Articles

Regulation of Graves’ Hyperthyroidism with Naturally Occurring CD4+CD25+ Regulatory T Cells in a Mouse Model

Graves' hyperthyroidism can be efficiently induced in susceptible mouse strains by repeated immunization with recombinant adenovirus coding the TSH receptor (TSHR). This study was designed to evaluate the role(s) played by naturally occurring CD4(+)CD25(+) regulatory T cells in the development of Graves' hyperthyroidism in resistant C57BL/6 and susceptible BALB/c mice. Depletion of CD4(+)CD25(+) T cells rendered some C57BL/6 mice susceptible to induction of hyperthyroidism. Thus, hyperthyroidism developed in 30% of the CD4(+)CD25(+) T cell-depleted C57BL/6 mice immunized with adenovirus expressing the TSHR A-subunit (AdTSHR289) vs. 0% of those immunized with AdTSHR289 alone. This immunological manipulation also enhanced disease severity in susceptible BALB/c mice, as reflected by a significant increase in mean T(4) levels by CD4(+)CD25(+) T cell depletion. The immunoenhancing effect of CD4(+)CD25(+) T cell depletion appears to be attributable to an increase in thyroid-stimulating antibody production and/or a decrease in thyroid-blocking antibody synthesis, but not immune deviation to either T helper 1 or 2 cells. Interestingly, unlike BALB/c mice, some hyperthyroid C57BL/6 mice showed some intrathyroidal lymphocytic infiltration with follicular destruction. These results indicate that CD4(+)CD25(+) T cells play a role in disease susceptibility and severity in adenovirus-TSHR-induced Graves' hyperthyroidism. Overall, the imbalance between effector and regulatory T cells appears to be crucial in the pathogenesis of Graves' disease.

H2 complex controls CD4/CD8 ratio, recurrent responsiveness to repeated stimulations, and resistance to activation-induced apoptosis during T cell response to mycobacterial antigens

Genetic variation in the major histocompatibility complex (MHC) influences susceptibility and immune responses to Mycobacterium tuberculosis in mice and humans, but connections among the severity of tuberculosis (TB), dynamic changes in T cell responses to mycobacteria, and MHC genetic polymorphisms are poorly characterized. The overall effect of the MHC genes on TB susceptibility and cellular responses to mycobacteria is moderate; thus, such studies provide reliable results only if congenic mouse strains bearing a variety of H2 haplotypes on an identical genetic background are analyzed. Using a panel of H2-congenic strains on the B10 background, we demonstrate that T cells from mice of three different strains, which are resistant to TB infection, readily respond by proliferation to repeated stimulations with mycobacterial sonicate, whereas T cells from three susceptible mouse strains die after the second stimulation with antigen. This difference is specific, as T cells from TB-susceptible and -resistant mouse strains do not differ in response to irrelevant antigens. The CD4/CD8 ratio in immune lymph nodes correlates strongly and inversely with TB susceptibility, being significantly lower in resistant mice as a result of an increased content of CD8+ cells. These differences between the two sets of mouse strains correlate with an elevated level of activation-induced T cell apoptosis in TB-susceptible mice and a higher proportion of activated CD44+ CD62 ligand- T cells in TB-resistant mice. These results may shed some light on the nature of the cellular basis of MHC-linked differences in susceptibility to TB.

Genomic Identification of Potential Risk Factors during Acetaminophen-Induced Liver Disease in Susceptible and Resistant Strains of Mice

Drug-induced liver disease (DILD) continues to cause significant morbidity and mortality and impair new drug development. Mounting evidence suggests that DILD is a complex, multifactorial disease in which no one factor is likely to be an absolute indicator of susceptibility. As an approach to better understand the multifactorial basis of DILD, we recently compared the hepatic proteomes of mice that were resistant (SJL) and susceptible (C57Bl/6) to APAP-induced liver disease (AILD) wherein we identified potential risk factors and mechanistic pathways responsible for DILD. In this study, we have uncovered additional potential risk factors by comparing hepatic mRNA expression profiles of the same two strains of mice with that of SJLxB6-F1 hybrid (F1) mice, which were found to be of intermediate susceptibility to AILD. Global hepatic gene expression profiling over a 24 h period following APAP treatment revealed elevated patterns in the mRNA expression of cytoprotective genes in resistant SJL mice as compared to susceptible B6 mice, while F1 mice had intermediate mRNA expression levels of these genes. One of these genes encoded for heat shock protein (HSP) 70 whose relative protein expression among the three strains of mice was found to parallel that of their mRNA levels, suggesting that this protein had a protective role against AILD. However, there was no difference in the susceptibility of HSP70 knockout (KO) mice to AILD as compared to wild-type (WT) mice. There were also protoxicant genes, such as osteopontin (OPN), with elevated mRNA expression levels in the B6 mice as compared to the SJL mice and with intermediate levels in the F1 mice, suggesting that they may play a role in exacerbating liver injury after APAP treatment. In support of this hypothesis, OPN KO mice were found to be more resistant to AILD than WT mice. Additionally, the results from both the proteomic and the genomic studies were compared. The two approaches were found to be complementary to each other and not simply overlapping. Our findings suggest that comparative gene expression analysis of susceptible and resistant mouse strains may lead to the identification of factors that could have a role in determining the susceptibility of individuals to DILD.

High transmission rates restore expression of genetically determined susceptibility of mice to nematode infections

This study investigated why the susceptible or resistance phenotype to the nematode Heligmosomoides polygyrus was lost when susceptible (C57BL/6) and resistant (Balb/c) strains of mice were housed together in indoor arenas with continuous transmission of the parasite larvae present in peat trays (Scott, 1991). First, both strains expressed their normal phenotype when given a controlled challenge while living in arenas, and when experimentally infected with only 5 parasite larvae. To test whether chronic exposure to peat altered the resistance phenotype, mice were given a challenge infection while living on peat. C57BL/6 mice living on peat had higher egg production and higher worm numbers than Balb/c mice, except at 2 months post-challenge. Finally, natural transmission rates were increased in arena experiments through either regular replacement of arena mice with naïve mice or direct introduction of additional larvae. A transient difference in infection levels between strains was detected in response to a modest increase in transmission whereas a 10-fold increase in transmission allowed C57BL/6 mice to exhibit the typical profile of high egg production and elevated worm numbers. These data indicate that C57BL/6 mice are less able to regulate parasite numbers at high transmission rates compared with lower transmission rates.

Defective Activation of ERK in Macrophages Lacking the p50/p105 Subunit of NF-κB Is Responsible for Elevated Expression of IL-12 p40 Observed after Challenge with Helicobacter hepaticus

Helicobacter hepaticus is an enterohepatic Helicobacter species that induces lower bowel inflammation in susceptible mouse strains, including those lacking the p50/p105 subunit of NF-kappaB. H. hepaticus-induced colitis is associated with elevated levels of IL-12 p40 expression, and p50/p105-deficient macrophages express higher levels of IL-12 p40 than wild-type macrophages after challenge with H. hepaticus. However, the molecular mechanisms by which the p50/p105 subunit of NF-kappaB suppresses IL-12 p40 expression have not yet been elucidated. In this study we have demonstrated that H. hepaticus challenge of macrophages induces ERK activation, and this event plays a critical role in inhibiting the ability of H. hepaticus to induce IL-12 p40. Activation of ERK requires both p50/p105 and the MAPK kinase kinase, Tpl-2. Inhibition of the induction of IL-12 p40 by ERK was independent of c-Rel, a known positive regulator of IL-12 p40. Instead, it was linked to the induction of c-Fos, a known inhibitor of IL-12 p40 expression. These results suggest that H. hepaticus induces ERK activation by a pathway dependent upon Tpl-2 and p105, and that activation of ERK inhibits the expression of IL-12 p40 by inducing c-Fos. Thus, a defect in ERK activation could play a pivotal role in the superinduction of IL-12 p40 observed after challenge of macrophages lacking the p50/p105 subunit of NF-kappaB with H. hepaticus.

Theiler’s virus induces the MIP-2 chemokine (CXCL2) in astrocytes from genetically susceptible but not from resistant mouse strains

The murine encephalomyelitis virus of Theiler (TMEV) induces demyelination in susceptible strains of mice by a CD4 + Th1 T cell mediated immunopathologic process. We focused on the production of one chemokine, the macrophage inflammatory protein-2 (MIP-2 or CXCL2), by cultured mouse astrocytes infected with the BeAn strain of TMEV. Analysis of a murine genome DNA hybridized with cRNA from mock- and TMEV-infected astrocytes, revealed up-regulation of three sequences encoding MIP-2. Northern blot analysis indicated increased MIP-2 mRNA expression. Levels of MIP-2 in the supernatants of infected cells as detected by ELISA, varied directly with the multiplicity of infection used. This secreted CXCL2 was biologically active inducing chemoattraction of neutrophils but not of lymphocytes. CXCL2 was specifically induced by TMEV infection, since induction was inhibited by anti TMEV antibodies. The inflammatory cytokines, IL-1α and TNF-α, which are also induced in astrocytes by TMEV, were very potent inducers of CXCL2. Nevertheless, both mechanisms of induction follows different pathways as antibodies to both cytokines fails to inhibit TMEV-induced CXCL2 up-regulation. Sera from TMEV-infected SJL/J mice with chronic demyelination, but not from BALB/c TMEV-resistant mice, revealed CXCL2 at the peak of clinical disease. Our main novel finding is the strain-dependent differences in CXCL2 expression both in vitro and in vivo. This suggest an role for this chemokine in attracting immune cells within the CNS, which in turn, might trigger demyelination in this experimental model of MS.

B1 cells contribution to susceptibility in experimental paracoccidioidomycosis: immunoglobulin isotypes and repertoire determination

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America. The experimental murine model has been used to approach the disease, with susceptible and resistant mice strains that reproduce most of the main human immunological features. Since the hypergammaglobulinemia observed in susceptible mice and humans might have an influence on B1 cells, we investigated its role during the experimental infection with Paracoccidiodes brasiliensis. CBA/Nxid mice, deficient in B1 cells, and CBA/Nxid reconstituted with B1 cells isolated from the non-mutant CBA/J strain were infected with 106 yeast forms of P. brasiliensis. At the 8th and 22nd week post infection the DTH response of CBA/Nxid mice was significantly higher after 24 h of P. brasiliensis antigens inoculation and the specific humoral response was reduced, in comparison to CBA/J or recCBA/Nxid. Production of NAbs is a hallmark of the B1 subset. Higher Ig productions to auto antigens such as DNA, MBP and RBC were observed in CBA/J infected mice or recCBA/Nxid. Anti P. brasiliensis IgG2a was produced by CBA/Nxid mice early in infection, while CBA/J or recCBA/Nxid presented increased levels of this isotype only after the 8th week of infection. Furthermore, western blotting analysis showed that CBA/Nxid mice expanded less clones against P. brasiliensis antigens, with weakly detectable anti-gp43 antibodies while CBA/J mice produce IgM anti-gp43 at the 2nd week of infection and IgG anti-gp43 at the 2nd and 8th week. On the other hand, recognition of gp70, a fungal antigen that, as gp43, inhibits macrophage activation was not compromised in B1 deficient mice. These results suggest that B1 cells might have influence in the kinetic of production of protective isotypes of immunoglobulins and their repertoire that could contribute to an early drive towards a Th2 response, affecting the cellular response in susceptible mice during experimental paracoccidiodomycosis.

Molecular characterization of an arthritogenic collagen peptide interacting with I‐Ar

Collagen-induced arthritis (CIA) is an autoimmune arthritis that can be elicited by the immunization of genetically susceptible strains of mice with type II collagen (CII). We have analysed the molecular interactions that occur between an arthritogenic T-cell determinant CII (442-457) and the murine class II susceptibility allele I-A(r). To determine which amino acid residues within the CII (442-457) sequence are responsible for binding to I-A(r), a soluble I-A(r):IgG2aFc fusion protein-peptide binding assay was developed. Various concentrations of analogue peptides were tested for their ability to compete with biotinylated CII (607-622) for binding to I-A(r), thereby establishing a relative comparison of the binding affinities among these analogues. Analogue peptides with substitutions at positions 447 (Ala --> Val), 448 (Gly --> Ala) and 451 (Gly --> Ala) bound poorly to the I-A(r) molecule. These data suggest that positions 447, 448 and 451 on CII are the major anchor points to I-A(r) molecules. In cytokine assays, only substitutions within positions 445-454 decreased the interferon-gamma production by T cells. These data narrow the core of the arthritogenic T-cell determinant to CII (445-454). Identification of the molecular interactions involved in T-cell recognition of CII should lead to antigen-specific means of inhibiting autoimmune arthritis.

Endogenous Platelet PF4 Promotes In Vivo Activated Protein C (APC) Generation and Survival after Lethal Lipopolysaccharide Challenge in Mice: A Potential Physiologic Role for PF4.

Pharmacologic infusion of activated protein C (APC) improves survival in human sepsis and genetically induced deficiencies in APC generation increase mortality in a murine lipopolysaccharide (LPS) model of inflammation/sepsis. We have shown that the platelet α-granule-specific chemokine, platelet factor 4 (PF4), accelerates thrombin·thrombomodulin complex APC generation in vitro and in vivo when recombinant PF4 is pharmacologically co-infused in a primate thrombin infusion model system. Hypothesizing a potential physiologic role for PF4 in stimulating APC formation in vivo, we tested whether variations in the level of endogenous platelet PF4 content affect APC generation and also influence survival in the murine LPS challenge model. To stimulate APC formation and platelet PF4 release in mice, we injected murine thrombin (80U/kg IV). Ten min after thrombin injection into wildtype (WT) C57BL/6J mice, plasma APC levels, assessed by enzyme capture amidolytic assay, increased ~10-fold over basal levels. Injection of concurrent murine PF4 (7.5 mg/kg IV) further increased APC levels 2-2.6-fold. We then studied APC generation in mice that were either completely deficient in PF4 (PF4−/−) or transgenic mice that had 6-fold normal levels of human PF4 (hPF4+), both of which had been crossbred onto the same C57BL/6J background >10 times. Plasma APC generation by thrombin was 74 ± 6% in the PF4−/− mice (n = 7) compared to WT littermates (n = 15, p<0.1) and increased to 178 ± 49% in hPF4+ mice (n= 22, p< 0.003 compared to WT (n= 36)). Heterozygous protein C deficient (PC+/−) mice had 65 ± 21% of WT APC generation (n= 5, p= 0.05 compared to WT (n=7)), but APC generation was restored to 96 ± 6% level in hPF4+/PC+/− mice (n= 6, p= 0.88 compared to WT (n=12)). Only PF4−/− and PC+/− mice died during this thrombin injection trial with mortality rates of 30% and 58%, respectively. A lethal LPS challenge model (25 mg/kg IP) was used to test the susceptibility of mouse strains with varying PF4 levels. Significant numbers of WT and PF4−/− mice died before the end of the first day [(18 of 44 (40% mortality) and 6 of 21 (28% mortality), respectively], while none of the 19 hPF4+ animals died (p< 0.001). However, after the first day, mortality did not differ significantly between the groups and final mortality for the three groups was ~70%. In summary, these studies of mice with varying platelet PF4 suggest that endogenous PF4 plays a physiologic role to stimulate APC production. Moreover, mice with high platelet PF4 content appear to be protected from both thrombin- and LPS-provoked deaths. This suggests that PF4 plays a physiologic role to enhance APC generation, that patients with high PF4 levels may be intrinsically protected from sepsis and supports the possibility that PF4 infusions in patients with sepsis may be a viable therapeutic strategy.

Active and passive immunization against oral Candida albicans infection in a murine model

Clinical and laboratory studies are consistent with a major role for cell-mediated immunity in recovery from oral infection with Candida albicans, but the role of humoral immunity remains controversial. The purpose of this study was to establish the relative contributions of cellular and humoral immunity to protection against oral candidiasis in a murine model, and to determine whether host responses could be enhanced by different immunization strategies. Active oral immunization was protective in BALB/c and CBA/CaH mice, reducing both fungal burden and duration of infection after secondary challenge, whereas systemic immunization failed to protect against subsequent oral challenge. Candida-specific IgM was the predominant antibody detected in serum following both primary and secondary oral challenge; however, Candida-specific salivary IgA was not detectable. Immunization by passive transfer of either lymphocytes or immune serum did not confer any significant protection against oral infection in either susceptible or resistant mouse strain. The data demonstrate a possible role for mucosa-associated immunity following active immunization by the oral route, most likely exerted by local T lymphocytes resident in the oral mucosa, but there was no evidence to support a role for humoral immunity in protection against oral candidiasis.

Systemic autoimmune disease induced by dendritic cells that have captured necrotic but not apoptotic cells in susceptible mouse strains

Systemic lupus erythematosus (SLE) is an autoimmune disorder of a largely unknown etiology. Anti-double-stranded (ds) DNA antibodies are a classic hallmark of the disease, although the mechanism underlying their induction remains unclear. We demonstrate here that, in both lupus-prone and normal mouse strains, strong anti-dsDNA antibody responses can be induced by dendritic cells (DC) that have ingested syngeneic necrotic (DC/nec), but not apoptotic (DC/apo), cells. Clinical manifestations of lupus were evident, however, only in susceptible mouse strains, which correlate with the ability of DC/nec to release IFN-gamma and to induce the pathogenic IgG2a anti-dsDNA antibodies. Injection of DC/nec not only accelerated disease progression in the MRL/MpJ-lpr/lpr lupus-prone mice but also induced a lupus-like disease in the MRL/MpJ-+/+ wild-type control strain. Immune complex deposition was readily detectable in the kidneys, and the mice developed proteinuria. Strikingly, female MRL/MpJ-+/+ mice that had received DC/nec, but not DC/apo, developed a 'butterfly' facial lesion resembling a cardinal feature of human SLE. Our study therefore demonstrates that DC/nec inducing a Th1 type of responses, which are otherwise tightly regulated in a normal immune system, may play a pivotal role in SLE pathogenesis.

Anamnestic Responses of Mice followingMycobacterium tuberculosisInfection

The anamnestic response is the property of the immune system that makes vaccine development possible. Although the development of a vaccine against Mycobacterium tuberculosis is an important global priority, there are many gaps in our understanding of how immunological memory develops following M. tuberculosis infection or after BCG vaccination. In experiments designed to compare the anamnestic response of susceptible and resistant mouse strains, major histocompatibility complex-matched memory-immune C3.SW-H2(b)/SnJ and C57BL/6 mice both demonstrated better control of bacterial replication following reinfection with M. tuberculosis than control mice. Nevertheless, this memory response did not appear to have any long-term protective effect for either mouse strain. A greater understanding of the immunological factors that govern the maintenance of immunological memory following exposure to M. tuberculosis will be required to develop an effective vaccine.

Genetic control of experimental spondylarthropathy

To characterize experimentally induced spondylarthropathy (SpA) in arthritis-susceptible inbred mice and in their F(1) and F(2) hybrid generations of susceptible and resistant mouse strains. SpA was induced in susceptible BALB/c and C3H/HeJCr (C3H) strains of mice, and in their F(1) and F(2) generations derived from intercrosses with arthritis- and/or spondylitis-resistant DBA/2 and DBA/1 parent strains, by systemic immunization with cartilage proteoglycan (PG) aggrecan. The incidence and severity of PG-induced spondylitis (PGIS) were scored histologically, and these scores for spine involvement were correlated with serum antibody and cytokine levels and with in vitro T cell responses to cartilage PG. PGIS was induced by systemic immunization with cartilage PG in adjuvant, and approximately 60-70% of susceptible mouse strains and their F(2) hybrids developed spondylitis either with or without arthritis. Adjuvants, particularly those activating the innate immune system and enforcing the Th1 dominance, had significant effects on the outcome and progression of SpA. The DBA/1 strain appeared to carry genes protecting this strain and its F(1) and F(2) hybrids from spondylitis, whereas the DBA/2 strain, although resistant to PGIS, harbored genes permitting PGIS in its hybrid generations. Arthritis- and/or spondylitis-susceptible BALB/c and C3H parent strains and their F(2) hybrids exhibited the highest incidence and severity of spondylitis. PGIS, a murine model of autoimmune spondylitis, shows similarities to ankylosing spondylitis. Segregation of susceptibility to PG-induced arthritis (PGIA) from that to PGIS in different genetic crosses suggests that PGIA and PGIS are separate diseases. Therefore, this model allows for the elucidation of genetic components involved in the etiology of SpA, independent of those controlling the susceptibility to PGIA.

Proteomic Identification of Potential Susceptibility Factors in Drug-Induced Liver Disease

Drug-induced liver disease (DILD) causes significant morbidity and mortality and impairs new drug development. Currently, no known criteria can predict whether a drug will cause DILD or what risk factors make an individual susceptible. Although it has been shown in mouse studies that the disruption of key regulatory factors, such as cyclooxygenase-2 (COX-2), interleukin (IL)-6, and IL-10, increased susceptibility to DILD caused by acetaminophen (APAP), no single factor seems to be absolute. As an approach to better understand the multifactorial basis of DILD, we compared the hepatic proteome of mice that are resistant (SJL) and susceptible (C57Bl/6) to APAP-induced liver disease (AILD), using solution-based isotope-coded affinity tag (ICAT) liquid chromatography mass spectrometry. Several novel factors were identified that were more highly expressed in the livers of SJL mice, including those involved in stress response, cell proliferation and tissue regeneration, and protein modification, implicating these proteins as potential hepatoprotective factors. There was also a selective loss of several mitochondrial proteins from the livers of the susceptible C57Bl/6 mice, suggesting that the loss of functional mitochondria may indeed play a role in AILD. These findings indicate that comparative hepatic proteomic analyses of susceptible and resistant mouse strains may provide a global approach for identifying potential risk factors and mechanistic pathways responsible for DILD.

Early development of primary biliary cirrhosis in female C57BL/6 mice because of poly I:C administration

Primary biliary cirrhosis (PBC) is one of the organ-specific autoimmune diseases characterized by destruction of the biliary epithelial cells, cholestasis, liver cirrhosis, and liver failure. With the postulation that induction of the autoimmune process might induce PBC-like cholangitis, here we used polyinosinic polycytidylic acid (poly I:C), an inducer of type-1 interferon (IFN), to generate an autoimmune cholangitis animal model. Female C57BL/6 mice were injected with 5 mg/kg of poly I:C twice a week for 28 consecutive weeks. Liver specimens were collected to evaluate the degree of cell infiltration. Autoantibodies, including antimitochondrial antibody (AMA), were assayed by immunofluorescence, enzyme-linked immunosorbent assay (ELISA) and immunoblotting. IFN-alpha was estimated in the sera by an ELISA method. Poly I:C injection induced IFN-alpha. Mononuclear cells were detected at the portal areas 8 weeks after the start of poly I:C injection, which progressed up to 16 weeks. Autoantibodies, including AMA, were detected in the sera from all poly I:C-injected mice. In conclusion, we show an early development of a PBC-like cholangitis in a genetically susceptible mouse strain because of poly I:C administration. This model would be helpful to study PBC immunopathogenesis and to evaluate the effectiveness of newly developed therapeutic regimens for PBC.

Cytolethal Distending Toxin Is Essential forHelicobacter hepaticusColonization in Outbred Swiss Webster Mice

Helicobacter hepaticus, which induces chronic hepatitis and typhlocolitis in susceptible mouse strains, produces a cytolethal distending toxin (CDT) consisting of CdtA, CdtB, and CdtC. A cdtB-deficient H. hepaticus isogenic mutant (HhcdtBm7) was generated and characterized for colonization parameters in four intestinal regions (jejunum, ileum, cecum, and colon) of outbred Swiss Webster (SW) mice. Inactivation of the cdtB gene abolished the ability of HhcdtBm7 to colonize female mice at both 8 and 16 weeks postinfection (wpi), whereas HhcdtBm7 colonized all of four intestinal regions of three of five males at 8 wpi and then was eliminated by 16 wpi. Wild-type (WT) H. hepaticus was detected in the corresponding intestinal regions of both male and female mice at 8 and 16 wpi; however, colonization levels of WT H. hepaticus in the cecum and colon of male mice were approximately 1,000-fold higher than in females (P < 0.0079) at 16 wpi. Infection with WT H. hepaticus, but not HhcdtBm7, at 8 wpi was associated with significantly increased mRNA level of ileal and cecal gamma interferon (IFN-gamma) in females (P < 0.016 and 0.031 between WT H. hepaticus-infected and sham-dosed females, respectively). In contrast, the mRNA levels of IFN-gamma were significantly higher in the colon (P < 0.0079) and trended to be higher in the cecum (P < 0.15) in the HhcdtBm7-colonized male mice versus the sham-dosed controls at 8 wpi. In addition, mRNA levels of ileal IFN-gamma were significantly higher in the control females than males at 8 wpi (P < 0.016). There were significantly higher Th1-associated immunoglobulin G2a (IgG2a), Th2-associated IgG1 and mucosal IgA (P < 0.002, 0.002, 0.002, respectively) responses in the mice infected with WT H. hepaticus when compared to HhcdtBm7 at 16 wpi. Colonic interleukin-10 (IL-10) expressions at 16 wpi were significantly lower in both female and male mice colonized by WT H. hepaticus or in males transiently colonized through 8 wpi by HhcdtBm7 versus control mice (P < 0.0159). These lines of evidence indicate that (i) H. hepaticus CDT plays a crucial role in the persistent colonization of H. hepaticus in SW mice; (ii) SW female mice are more resistant to H. hepaticus colonization than male mice; (iii) there was persistent colonization of WT H. hepaticus in cecum, colon, and jejunum but only transient colonization of H. hepaticus in the ileum of female mice; (iv) H. hepaticus colonization was associated with down-regulation of colonic IL-10 production.

Candidate Gene for Tuberculosis Resistance

A gene that, when mutated, appears to confer mice with susceptibility to tuberculosis has been identified and is likely to function in signaling between nuclear receptors, interferon, and pathogens. Pan et al. studied the sst1 locus (super-susceptibility to tuberculosis) in mice. Mice with mutations that caused susceptibility showed increased proliferation of Mycobacterium tuberculosis in the lungs after infection compared with that in control animals. In susceptible animals, macrophages underwent necrosis after infection, whereas those from resistant animals underwent apoptosis. The authors identified a gene, Ipr1 (intracellular pathogen resistance 1), that was expressed in resistant cells in response to infection with M. tuberculosis but not expressed in the susceptible strain. Restoration of a full-length copy of Ipr1 into the susceptible mouse strain decreased bacterial proliferation in the lungs and caused cultured macrophages to undergo apoptosis, rather than necrosis, after infection. Growth of M. tuberculosis or of another pathogen, L. monocytogenes , was suppressed in macrophages with the restored Ipr1 gene. Thus, the Ipr1 protein may help trigger innate immune responses to multiple intracellular pathogens. Exactly how it does so remains unclear, but the predicted protein product contains a domain structure indicative of a role in signaling. It contains protein-protein interaction domains, a chromatin-binding (SAND) domain, a nuclear localization signal, and a nuclear receptor-binding motif. The expression of Ipr1 , and that of its human homolog ( SP110 ), is regulated by interferons, and the SP110 protein appears to directly interact with viral proteins. Thus, the authors propose that Ipr1 may integrate signals in response to pathogens or viruses that alter gene expression and promote apoptosis of host cells. Many humans are resistant to tuberculosis, but more than two million individuals die of the disease each year. H. Pan, B.-S. Yan, M. Rojas, Y. V. Shebzukhov, H. Zhou, L. Kobzik, D. E. Higgins, M. J. Daly, B. R. Bloom, I. Kramnik, Ipr1 gene mediates innate immunity to tuberculosis. Nature 434 , 767-772 (2005). [PubMed]

Critical Role of Macrophage Migration Inhibitory Factor Activity in Experimental Autoimmune Diabetes

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that plays a pivotal role in several immunoinflammatory and autoimmune diseases. In this study we examined the role of MIF in the development of immunoinflammatory diabetes induced in susceptible strains of mice by multiple low doses of streptozotocin. We found that MIF protein was significantly elevated in islet cells during the development of diabetes, and that targeting MIF activity with either neutralizing antibody or the pharmacological inhibitor (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester, markedly reduced clinical and histopathological features of the disease, such as hyperglycemia and insulitis. Lymphocytes from mice treated with the MIF inhibitors exhibited reduction of both islet antigen-specific proliferative responses and adhesive cell-cell interactions. Neutralization of MIF also down-regulated the ex vivo secretion of the proinflammatory mediators, TNF-alpha, interferon-gamma, and nitric oxide, while augmenting that of the antiinflammatory cytokine, IL-10. This study provides the first in vivo evidence for a critical role for MIF in the immune-mediated beta-cell destruction in an animal model of human type 1 diabetes mellitus and identifies a new therapeutic strategy for the prevention and treatment of this disease in humans that is based on the selective inhibition of MIF activity.

COX-2 inhibitors and genetic background reduce mammary tumorigenesis in cyclooxygenase-2 transgenic mice

Cyclooxygenase-2 (COX-2) overexpression is a widely recognized feature of human breast cancer and inhibitors of the enzyme have antitumor effects in a subset of tumor settings. Previously, we demonstrated that direct overexpression of COX-2 under control of the mammary-specific MMTV promoter/enhancer, was itself oncogenic and lead to the induction of mammary tumors in multiparous, outbred CD1 mice. In the present study, we provide evidence that COX-2 dependent tumor progression can also be studied in FVB/N, an inbred strain widely used for analysis of breast cancer progression. In these mice, the human COX-2 transgene was strongly induced during pregnancy/lactation and mammary tumors developed after multiple pregnancies. However, crossing the COX-2 FVB/N mice with the C57BL6 strain resulted in loss of the mammary tumorigenic phenotype despite the fact that the human COX-2 gene was induced. Treatment of the COX-2 transgenic mice in the FVB/N strain with celecoxib (1600 ppm), a COX-2 selective inhibitor, resulted significant reduction in tumor size and multiplicity when compared to transgenic mice fed with control chow. SC-560 (20 ppm), a COX-1 selective inhibitor did not have significant effect on tumorigenesis. These studies suggest that FVB/N is a susceptible mouse strain well suited to the study of COX-2 mediated tumor progression and may provide a tool for the identification of interacting genes and therapeutic treatments for this clinically important target.

Producción de anticuerpos IgG1 anti-glucuronoxilomanana en ratones resistentes a la criptococosis

Cryptococcus neoformans is a widely disseminated fungus shown to be responsible for infections in individuals with impaired cell mediated immunity, such as patients with human immunodeficiency virus (HIV). Cryptococcus neoformans has a polysaccharide capsule composed of glucuronoxylomannan (GXM), which acts as a major virulence factor and is considered to be a thymus independent type-2 antigen (TI-2). In the current study, the production kinetics were evaluated for IgG subclasses specific for GXM, and assessed with the cross reactive antibodies to Streptococcus pneumoniae polysaccharide. In addition, spleen B cell subpopulations were quantified in murine models of cryptococcosis with different susceptibilities to the infection. Antibodies were detected by ELISA at different time intervals after C. neoformans infection in moderately resistant (Balb/c), highly resistant (CBA/j) and susceptible (C57BL/6) mouse strains. B cells subpopulations were determined by flow cytometry analysis. Early production of IgG1, described as protector antibodies, coincided with a decrease of the number of C. neoformans colony forming units in the lungs. Polysaccharide cross-reactive antibodies were detected in each of the three mouse strains. Antibody titers were highest in the susceptible strain (C57BL/6), a strain which also showed the highest proportion of splenic CD5+ B lymphocytes. In contrast, CBA/J mice showed the highest levels of CD43+ B. These findings suggest that IgG1 antibodies specific for GXM, are implicated in host protection against C. neoformans infection and may be regulated by CD43+ cells. They also suggest that cross reactivity antibodies are not important in the protection against C. neoformans infection.