Increased generation of dendritic cells from myeloid progenitors in autoimmune-prone nonobese diabetic mice

Aberrant dendritic cell (DC) development and function may contribute to autoimmune disease susceptibility. To address this hypothesis at the level of myeloid lineage-derived DC we compared the development of DC from bone marrow progenitors in vitro and DC populations in vivo in autoimmune diabetes-prone nonobese diabetic (NOD) mice, recombinant congenic nonobese diabetes-resistant (NOR) mice, and unrelated BALB/c and C57BL/6 (BL/6) mice. In GM-CSF/IL-4-supplemented bone marrow cultures, DC developed in significantly greater numbers from NOD than from NOR, BALB/c, and BL/6 mice. Likewise, DC developed in greater numbers from sorted (lineage(-)IL-7Ralpha(-)SCA-1(-)c-kit(+)) NOD myeloid progenitors in either GM-CSF/IL-4 or GM-CSF/stem cell factor (SCF)/TNF-alpha. [(3)H]TdR incorporation indicated that the increased generation of NOD DC was due to higher levels of myeloid progenitor proliferation. Generation of DC with the early-acting hematopoietic growth factor, flt3 ligand, revealed that while the increased DC-generative capacity of myeloid-committed progenitors was restricted to NOD cells, early lineage-uncommitted progenitors from both NOD and NOR had increased DC-generative capacity relative to BALB/c and BL/6. Consistent with these findings, NOD and NOR mice had increased numbers of DC in blood and thymus and NOD had an increased proportion of the putative myeloid DC (CD11c(+)CD11b(+)) subset within spleen. These findings demonstrate that diabetes-prone NOD mice exhibit a myeloid lineage-specific increase in DC generative capacity relative to diabetes-resistant recombinant congenic NOR mice. We propose that an imbalance favoring development of DC from myeloid-committed progenitors predisposes to autoimmune disease in NOD mice.     

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.     

Genetic segregation of inflammatory lung disease and autoimmune disease severity in SHIP-1-/- mice

Alternatively activated M2 macrophages are implicated as both regulators and agents of lung disease, but their control is poorly understood. SHIP-1 is a 5' inositol phosphatase that negatively regulates the PI3K signaling pathway implicated in inflammation. SHIP-1-deficient mice have defects in hematopoiesis and B cell development, and die prematurely due to consolidation of lungs with M2-skewed macrophages. SHIP-1 is thought to restrain M2 macrophage polarization, with deregulated M2 skewing coinciding with severe lung disease in SHIP-1-deficient mice. To determine the influence of genetic background on the lung phenotype in SHIP-1(-/-) mice, we backcrossed the SHIP-1 null mutation onto C57BL/6 (Th2-resistant) and BALB/c (Th2-prone) backgrounds. Remarkably, we found that inflammatory lung disease was severe in C57.SHIP-1(-/-) mice, but absent in BALB.SHIP-1(-/-) mice. C57.SHIP-1(-/-), but not BALB.SHIP-1(-/-) mice had greatly increased myeloid progenitors, myeloid hyperplasia, markedly enhanced numbers of activated alveolar macrophages, and elevated amounts of Th2 and proinflammatory cytokines in bronchoalveolar lavage fluid and serum, suggesting that deregulated cytokine production induced disease. C57.SHIP-1(-/-) mice also developed severe B cell-dependent autoimmune disease, which was markedly attenuated on the BALB/c background. These data demonstrate that, contrary to current concepts, loss of SHIP-1 alone is not sufficient to cause lung inflammation, with disease only manifest on a permissive genetic background. This finding questions the nature of the lung disease in SHIP-1(-/-) mice, suggesting that its M2 classification is not strictly correct. Future identification of disease-promoting loci might reveal determinants of comorbid lung disease and autoimmunity and uncover potentially useful therapeutic targets.     

Distinct subsets of dendritic cells regulate the pattern of acute xenograft rejection and susceptibility to cyclosporine therapy

We determined whether distinct subclasses of dendritic cells (DC) could polarize cytokine production and regulate the pattern of xenograft rejection. C57BL/6 recipients, transplanted with Lewis rat hearts, exhibited a predominantly CD11c(+)CD8alpha(+) splenic DC population and an intragraft cytokine profile characteristic of a Th1-dominant response. In contrast, BALB/c recipients of Lewis rat heart xenografts displayed a predominantly CD11c(+)CD8alpha(-) splenic DC population and IL-4 intragraft expression characteristic of a Th2 response. In addition, the CD11c(+)IL-12(+) splenic DC population in C57BL/6 recipients was significantly higher than that in BALB/c recipients. Adoptive transfer of syngeneic CD8alpha(-) bone marrow-derived DC shifted a Th1-dominant, slow cell-mediated rejection to a Th2-dominant, aggressive acute vascular rejection (AVR) in C57BL/6 mice. This was associated with a cytokine shift from Th1 to Th2 in these mice. In contrast, transfer of CD8alpha(+) bone marrow-derived DC shifted AVR to cell-mediated rejection in BALB/c mice and significantly prolonged graft survival time from 6.0 +/- 0.6 days to 14.2 +/- 0.8 days. CD8alpha(+) DC transfer rendered BALB/c mice susceptible to cyclosporine therapy, thereby facilitating long-term graft survival. Furthermore, CD8alpha(+) DC transfer in IL-12-deficient mice reconstituted IL-12 expression, induced Th1 response, and attenuated AVR. Our data suggest that the pattern of acute xenogeneic rejection can be regulated by distinct DC subsets.     

Host genetic background affects regulatory T-cell activity that influences the magnitude of cellular immune response against Mycobacterium tuberculosis

Using two mouse strains with different abilities to generate interferon (IFN)-γ production after Mycobacterium tuberculosis infection, we tested the hypothesis that the frequency and activity of regulatory T (Treg) cells are influenced by genetic background. Our results demonstrated that the suppressive activity of spleen Treg cells from infected or uninfected BALB/c mice was enhanced, inhibiting IFN-γ and interleukin (IL)-2 production. Infected C57BL/6 mice exhibited a decrease in the frequency of lung Treg cells and an increased ratio CD4(+):CD4(+)Foxp3(+) cells compared with infected BALB/c mice and uninfected C57BL/6 mice. Moreover, infected C57BL/6 mice also had a decrease in the immunosuppressive capacity of spleen Treg cells, higher lung IFN-γ and IL-17 production, and restricted the infection better than BALB/c mice. Adoptive transfer of BALB/c Treg cells into BALB/c mice induced an increase in bacterial colony-forming unit (CFU) counts. Furthermore, BALB/c mice treated with anti-CD25 antibody exhibited lung CFU counts significantly lower than mice treated with irrelevant antibody. Our results show that in BALB/c mice, the Treg cells have a stronger influence than that in C57BL/6 mice. These data suggest that BALB/c and C57BL/6 mice may use some different mechanisms to control M. tuberculosis infection. Therefore, the role of Treg cells should be explored during the development of immune modulators, both from the perspective of the pathogen and the host.     

Hematologic disease induced in BALB/c mice by a bcr-abl retrovirus is influenced by the infection conditions.

Irradiated mice reconstituted with bone marrow cells infected with a retrovirus carrying the bcr-abl oncogene of human chronic myeloid leukemia are subject to a range of neoplastic hematopoietic diseases, both myeloid and lymphoid. Comparison of DBA/2 and C57BL/6 mice has revealed a marked strain difference in susceptibility to the various tumor types. The present study, performed with BALB/c mice, indicates that the kinetics and nature of the induced disease can be modulated by the infection procedure, as well as the genetic background, and that retroviral regulatory sequences may influence the outcome. A distinctive clonal myeloproliferative disorder, somewhat akin to chronic myeloid leukemia but with prominent erythroid and mast cell components, as well as granulocytic excess, was characterized.     

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.     

Studies of CD4- CD8- alpha beta bone marrow T cells with suppressor activity.

The predominant T cell subset in the bone marrow of specific pathogen-free C57BL/Ka and BALB/c mice expressed the alpha beta+ TCR CD4- CD8- surface phenotype. Purified C57BL/Ka alpha beta+ TCR CD4- CD8- marrow cells obtained by cell sorting suppressed the MLR of C57BL/Ka responder and BALB/c stimulator spleen cells. Although the percentage of typical T cells in the spleen was markedly reduced in adult nude mice or normal neonatal mice as compared to the normal adult, the percentage of alpha beta+ TCR CD4- CD8- cells in the spleen and marrow was not. The percentage of "self-reactive" V beta 5+ T cells in the BALB/c spleen was markedly reduced as compared to that in the C57BL/Ka spleen. However, the percentages in the bone marrow were similar. The results indicate that the predominant subset of marrow T cells in these pathogen-free mice differ with regard to surface marker phenotype, function, dependence on the adult thymus, and deletion of certain self-reactive V beta receptors as compared to typical spleen T cells. The marrow T cells appear to develop directly from marrow precursors without rearranged beta chain genes during a 48 hour in vitro culture.     

A lupus-suppressor BALB/c locus restricts IgG2 autoantibodies without altering intrinsic B cell-tolerance mechanisms

FcgammaR2B-deficient mice develop autoantibodies and glomerulonephritis with a pathology closely resembling human lupus when on the C57BL/6 (B6) background. The same mutation on the BALB/c background does not lead to spontaneous disease, suggesting differences in lupus susceptibility between the BALB/c and B6 strains. An F2 genetic analysis from a B6/BALB cross identified regions from the B6 chromosomes 12 and 17 with positive linkage for IgG autoantibodies. We have generated a congenic strain that contains the suppressor allele from the BALB/c chromosome 12 centromeric region (sbb2(a)) in an otherwise B6.FcgammaR2B(-/-) background. None of the B6.FcgammaR2B(-/-)sbb2(a/a) mice tested have developed IgG autoantibodies in the serum or autoimmune pathology. Mixed bone marrow reconstitution experiments indicate that sbb2(a) is expressed in non-B bone marrow-derived cells and acts in trans. sbb2(a) does not alter L chain editing frequencies of DNA Abs in the 3H9H/56R H chain transgenic mice, but the level of IgG2a anti-DNA Abs in the serum is reduced. Thus, sbb2(a) provides an example of a non-MHC lupus-suppressor locus that protects from disease by restricting the production of pathogenic IgG isotypes even in backgrounds with inefficient Ab editing checkpoints.     

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.     

Three methods for producing fertile hemopoietic chimeras in mice

Three methods for producing semiallogeneic (F1----parental) hemopoietic chimeras with retained or regained fertility are detailed here. Prenatal (PN) chimeras were produced by injecting F1 ([BALB/c female x C3H/HeJ male] or [CBA/J female x C57BL/6 male]) fetal liver (days 13-18) or adult bone marrow cells (10(6)-10(7) cells/20 microliters/embryo) into the yolk-sac cavities of days 13-17 gestation BALB/c or CBA/J embryos, respectively, and allowing them to be born naturally. Neonatal (NN) chimeras were made by introducing F1 bone marrow cells (1-2 x 10(7) cells/0.25 ml) into newborn (less than 24 hr old) female mice through the anterior facial vein. Female mice were raised to maturity in both cases. Ovary-transplanted (OT) chimeras were made by first irradiating (9.5 Gy) and repopulating young female adult mice with 10(7) F1 bone marrow cells, followed by bilateral orthotopic transplantation of syngeneic ovarian tissue six weeks later. Females reconstituted with the above three methods were mated with normal syngeneic males and sacrificed at 11-16 days of pregnancy to evaluate hemopoietic chimerism. This was determined in all cases by a radioautographic evaluation of the extent of donor H-2 phenotype marker expression on splenic small lymphocytes, after an indirect labelling of single-cell suspensions with monospecific antibody and [125I]protein-A. Results indicate that hemopoietic chimerism was best in the PN group (0.3-78.1%, mean = 27.1); intermediate in the OT group (5.8-38.2%, mean = 18.1); and low in the NN group (0-14%, with one exception, which was 83.6%). Observed fertility was best for BALB/c host PN chimeras.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development of donor-derived thymic lymphomas after allogeneic bone marrow transplantation in AKR/J mice

The transplantation of bone marrow cells from BALB/c (but not C57BL/6 and C3H/HeN) mice was observed to lead to the development of thymic lymphomas (leukemias) in AKR/J mice. Two leukemic cell lines, CAK1.3 and CAK4.4, were established from the primary culture of two thymic lymphoma, and surface phenotypes of these cell lines found to be H-2d and Thy-1.2+, indicating that these lymphoma cells are derived from BALB/c donor bone marrow cells. Further analyses of surface markers revealed that CAK1.3 is L3T4+ Lyt2+ IL2R-, whereas CAK4.4 is L3T4- Lyt2- IL2R+. Both CAK1.3 and CAK4.4 were transplantable into BALB/c but not AKR/J mice, further indicating that these cells are of BALB/c bone marrow donor origin. The cells were found to produce XC+-ecotropic viruses, but xenotropic and mink cell focus-forming viruses were undetectable. Inasmuch as thymic lymphomas are derived from bone marrow cells of leukemia-resistant BALB/c strain of mice under the allogeneic environment of leukemia-prone AKR/J mice, this animal model may serve as a useful tool not only for the analysis of leukemic relapse after bone marrow transplantation but also for elucidation of the mechanism of leukemogenesis.     

Adaptive differentiation of H-2- and Igh-restricted B lymphocyte in tetraparental bone marrow chimera

Immunization of BALB/c mice with MOPC-104E myeloma protein induced idiotype-specific enhancing B cells that acted on anti-dextran antibody producing B cells. The enhancing cells have the surface phenotype of B cells. With the use of several H-2 or Igh congenic mice, it was found that the cooperation among B cells was controlled by both the major histocompatibility complex (MHC) and Igh. The capability to generate enhancing B cell activity was analyzed by using tetraparental bone marrow chimeras. (C57BL/6 X BALB/c)F1 mice, for example, were lethally irradiated and were reconstituted with C57BL/6 and BALB/c bone marrow cells. Nine to 12 wk after the reconstitution, the chimeras were immunized with the myeloma protein and were tested for their enhancing B cell activity. After the removal of C57BL/6 origin cells by treatment with anti-H-2b + complement, residual cells exhibited enhancing B cell activity on BALB.B, as well as BALB/c antidextran antibody response. This indicates that the generation of H-2-restricted, idiotype-specific enhancing B cell activity differentiated adaptively so as to recognize foreign MHC as self under chimeric conditions. On the other hand, splenic B cells treated with anti-H-2d + complement did not enhance the responses of BALB/c or BALB.B. Even in a chimeric environment, the B cells of C57BL/6 origin could not obtain the ability to generate enhancing B cell activity upon immunization of the idiotype. The results described here, taken in conjunction with our previous studies, suggest that the Ig heavy chain gene(s) predominantly control the Igh restriction properties of enhancing B cells, and the capability of MHC recognition by B cells is selected under chimeric conditions.     

Helicobacter pylori infection in wild-type and cytokine-deficient C57BL/6 and BALB/c mouse mutants

Helicobacter pylori causes gastroduodenal ulcer disease in humans. T lymphocytes and their cytokines are thought to play a substantial role in the control of H. pylori infection. To determine the importance of T helper (Th) cytokines and background genes we investigated the natural course of H. pylori infection in BALB/c and C57BL/6 wild-type or mutant mice deficient for either interleukin (IL)-4 or interferon (IFN)-gamma. H. pylori SPM 326 persisted for at least six months in C57BL/6 but was cleared by BALB/c wild-type mice nine weeks postinfection. H. pylori was recovered more frequently from IFN-gamma(-/-) BALB/c and IFN-gamma( -/-) C57BL/6 mice than from the respective wild-type animals. In contrast, IL-4 deficiency had no detectable effect on H. pylori recovery rates from either strain of mice. Our data suggest a protective role of IFN-gamma by mediating inflammation in murine H. pylori infection. In addition, our data emphasize that background genes which differ between BALB/c and C57BL/6 mice regulate the clearance of H. pylori.     

IL-4 is required to prevent filarial nematode development in resistant but not susceptible strains of mice

The murine Litomosoides sigmodontis model of filarial infection provides the opportunity to elucidate the immunological mechanisms that determine whether these nematode parasites can establish a successful infection or are rejected by the mammalian host. BALB/c mice are fully susceptible to L. sigmodontis infection and can develop patent infection, with the microfilarial stage circulating in the bloodstream. In contrast, mice on the C57BL background are largely resistant to the infection and never produce a patent infection. In this study, we used IL-4 deficient mice on the C57BL/6 background to address the role of IL-4 in the development of L. sigmodontis parasites in a resistant host. Two months after infection, adult worm recovery and the percentage of microfilaraemic mice in infected IL-4 deficient mice were comparable with those of the susceptible BALB/c mice while, as expected, healthy adults were not recovered from wild type C57BL/6 mice. The cytokine and antibody responses reveal that despite similar parasitology the two susceptible strains (BALB/c and IL-4 deficient C57BL/6) have markedly different immune responses: wild type BALB/c mice exhibit a strong Th2 immune response and the IL-4 deficient C57BL/6 mice exhibit a Th1 response. We also excluded a role for antibodies in resistance through infection of B-cell deficient C57BL/6 mice. Our data suggest that the mechanisms that determine parasite clearance in a resistant/non-permissive host are Th2 dependent but that in a susceptible/permissive host, the parasite can develop in the face of a Th2 dominated response.     

Cutting edge: Fc receptor type I for IgG on macrophages and complement mediate the inflammatory response in immune complex peritonitis

The contributions of Fc receptors (FcRs) for IgG (FcgammaRs) and complement to immune complex (IC)-mediated peritonitis were evaluated in BALB/c-, C57BL/6-, FcRgamma chain-, and FcR type III for IgG (FcgammaRIII)-deficient mice, backcrossed to the C57BL/6 background. In BALB/c mice, but not in C57BL/6 mice, neutrophil migration was markedly attenuated after complement depletion. In mice lacking FcRgamma chain, neutrophil migration was abolished, whereas it was unaffected in FcgammaRIII-deficient mice. Huge amounts of TNF-alpha (TNF) were found in the peritoneal exudate of BALB/c and C57BL/6 mice but were absent in mice lacking FcRgamma chain or FcgammaRIII. Surprisingly, a functional inhibition of TNF in BALB/c and C57BL/6 mice had no effect on neutrophil infiltration. These data provide evidence that in IC peritonitis, the activation of FcR type I for IgG on peritoneal macrophages and the activation of the complement cascade, but not the interaction of ICs with FcgammaRIII and the subsequent release of TNF, initiate the inflammatory response in BALB/c and C57BL/6 mice.     

Inhibition of murine AIDS (MAIDS), development by the transplantation of bone marrow cells carrying the Fv-4 resistance gene to MAIDS virus-infected mice.

To examine whether the resistance allele of the Fv-4 gene (the Fv-4r gene) is a dominant inhibitory-product-encoding gene which an be used to prevent the development of murine AIDS (MAIDS), bone marrow cells from BALB/c-Fv-4wr mice were transplanted into BALB/c mice and C57BL/6 mice infected with MAIDS virus. Almost all of the virus-infected BALB/c and C57BL/6 mice developed MAIDS within 4 months and died 2 or 3 months later. However, when the virus-infected mice were subjected to cobalt irradiation and then given an intravenous injection of 10(7) BALB/c-Fv-4wr mouse bone marrow cells, the recipient mice survived much longer than the untreated mice, which suggests that the Fv-4 gene is a dominant inhibitory gene that is potentially useful in gene therapy of MAIDS.     

Polymorphisms in IL-4R alpha correlate with airways hyperreactivity, eosinophilia, and Ym protein expression in allergic IL-13-/- mice

The development of airways hyperreactivity in allergic IL-13(-/-) mice is controversial and appears to correlate with the number of times that the original 129 x C57BL/6 founder strain has been crossed to the BALB/c background. In this investigation, we compared allergic responses in founder IL-13(-/-) mice crossed for either 5 (N5) or 10 (N10) generations to BALB/c mice. Whereas allergic N5 IL-13(-/-) mice developed airways hyperreactivity, tissue eosinophilia, elevated IgE, and pulmonary expression of Ym proteins, these processes were attenuated in N5 IL-13(-/-) mice treated with an IL-4-neutralizing Ab, and in N10 IL-13(-/-) mice. These data showed that IL-4 was more effective in regulating allergic responses in N5 IL-13(-/-) mice than in N10 IL-13(-/-) mice. To elucidate the mechanism associated with these observations, we show by restriction and sequence analysis that N5 IL-13(-/-) mice express the C57BL/6 form of IL-4Ralpha and N10 IL-13(-/-) mice express the BALB/c form. Despite the near identical predicted molecular mass of these isoforms, IL-4Ralpha from N5 IL-13(-/-) mice migrates with a slower electrophoretic mobility than IL-4Ralpha from N10 IL-13(-/-) mice, suggesting more extensive posttranslational modification of the N5 form. The Thre(49)Ile polymorphism in the extracellular domain of BALB/c IL-4Ralpha has been demonstrated to disrupt N-linked glycosylation of Asn(47) and increase the dissociation rate of the IL-4Ralpha/IL-4 interaction. Collectively, these data show that polymorphisms in IL-4Ralpha, which have been shown to affect the interaction with IL-4, correlate with the ability of IL-4 to regulate allergic responses in IL-13(-/-) mice.     

Enalapril protects mice from pulmonary hypertension by inhibiting TNF-mediated activation of NF-kappaB and AP-1

The present study was undertaken to investigate the effects of treatment with the angiotensin-converting enzyme (ACE) inhibitor enalapril in a mouse model of pulmonary hypertension induced by bleomycin. Bleomycin-induced lung injury in mice is mediated by enhanced tumor necrosis factor-alpha (TNF) expression in the lung, which determines the murine strain sensitivity to bleomycin, and murine strains are sensitive (C57BL/6) or resistant (BALB/c). Bleomycin induced significant pulmonary hypertension in C57BL/6, but not in BALB/c, mice; average pulmonary arterial pressure (PAP) was 26.4 +/- 2.5 mmHg (P < 0.05) vs. 15.2 +/- 3 mmHg, respectively. Bleomycin treatment induced activation of nuclear factor (NF)-kappaB and activator protein (AP)-1 and enhanced collagen and TNF mRNA expression in the lung of C57BL/6 but not in BALB/c mice. Double TNF receptor-deficient mice (in a C57BL/6 background) that do not activate NF-kappaB or AP-1 in response to bleomycin did not develop bleomycin-induced pulmonary hypertension (PAP 14 +/- 3 mmHg). Treatment of C57BL/6 mice with enalapril significantly (P < 0.05) inhibited the development of pulmonary hypertension after bleomycin exposure. Enalapril treatment inhibited NF-kappaB and AP-1 activation, the enhanced TNF and collagen mRNA expression, and the deposition of collagen in bleomycin-exposed C57BL/6 mice. These results suggest that ACE inhibitor treatment decreases lung injury and the development of pulmonary hypertension in bleomycin-treated mice.     

NZB mice exhibit a primary T cell defect in fetal thymic organ culture

Defects in T cell development have been suggested to be a factor in the development of systemic autoimmunity in NZB mice. However, the suggestion of a primary T cell defect has often been by extrapolation, and few direct observations of T cell precursors in NZB mice have been performed. Moreover, the capacity of NZB bone marrow T cell precursors to colonize the thymus and the ability of the NZB thymic microenvironment to support T lymphopoiesis have not been analyzed. To address this important issue, we employed the fetal thymic organ culture system to examine NZB T cell development. Our data demonstrated that NZB bone marrow cells were less efficient at colonizing fetal thymic lobes than those of control BALB/c or C57BL/6 mice. In addition, NZB bone marrow cells did not differentiate into mature T cells as efficiently as bone marrow cells from BALB/c or C57BL/6 mice. Further analysis revealed that this defect resulted from an intrinsic deficiency in the NZB Lin-Sca-1+c-kit+ bone marrow stem cell pool to differentiate into T cells in fetal thymic organ culture. Taken together, the data document heretofore unappreciated deficiencies in T cell development that may contribute to the development of the autoimmune phenotype in NZB mice.