Role of the Fas/FasL system in a model of RSV infection in mechanically ventilated mice

Infection with respiratory syncytial virus (RSV) in children can progress to respiratory distress and acute lung injury necessitating mechanical ventilation (MV). MV enhances apoptosis and inflammation in mice infected with pneumonia virus of mice (PVM), a mouse pneumovirus that has been used as a model for severe RSV infection in mice. We hypothesized that the Fas/Fas ligand (FasL) system, a dual proapoptotic/proinflammatory system involved in other forms of lung injury, is required for enhanced lung injury in mechanically ventilated mice infected with PVM. C57BL/6 mice and Fas-deficient ("lpr") mice were inoculated intratracheally with PVM. Seven or eight days after PVM inoculation, the mice were subjected to 4 h of MV (tidal volume 10 ml/kg, fraction of inspired O(2) = 0.21, and positive end-expiratory pressure = 3 cm H(2)O). Seven days after PVM inoculation, exposure to MV resulted in less severe injury in lpr mice than in C57BL/6 mice, as evidenced by decreased numbers of polymorphonuclear neutrophils in the bronchoalveolar lavage (BAL), and lower concentrations of the proinflammatory chemokines KC, macrophage inflammatory protein (MIP)-1α, and MIP-2 in the lungs. However, when PVM infection was allowed to progress one additional day, all of the lpr mice (7/7) died unexpectedly between 0.5 and 3.5 h after the onset of ventilation compared with three of the seven ventilated C57BL/6 mice. Parameters of lung injury were similar in nonventilated mice, as was the viral content in the lungs and other organs. Thus, the Fas/FasL system was partly required for the lung inflammatory response in ventilated mice infected with PVM, but attenuation of lung inflammation did not prevent subsequent mortality.     

Genetic resistance to lethal Sendai virus pneumonia: virus replication and interferon production in C57BL/6J and DBA/2J mice

Resistant C57BL/6J and susceptible DBA/2J mice were exposed to aerosols of Sendai virus and killed at intervals to 12 days. Lungs were removed and assayed for infectious virus and interferon. Mean virus titers were 6 to 400 times higher in DBA/2J mice than in C57BL/6J mice 3 to 10 days after exposure. Mean interferon titers were 10 to 140 times higher in DBA/2J mice than in C57BL/6J mice 4 to 7 days after exposure. These results suggest that genetic resistance to the lethal effects of Sendai virus is expressed through control of viral replication within the first 72 hours of infection and that early expression of inherited resistance is not regulated by interferon.     

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.     

Respiratory syncytial virus infection in C57BL/6 mice: clearance of virus from the lungs with virus-specific cytotoxic T cells.

We describe respiratory syncytial virus (RSV)-specific cytotoxic T-cell (CTL) lines and clones developed from the spleens of C57BL/6 and BALB/c mice. Line 7 and clones derived from it were H-2Kb restricted, whereas line 12 had both Kb and Db components. Both lines, and all the clones except one, could lyse targets infected with either strain A or strain B RSV. Line 7 or 7-11E1 cells (8 x 10(6) to 10 x 10(6) given intravenously cleared RSV from the lungs of infected mice. There was no morbidity or mortality in any of the infected mice whether or not they received T cells. The C57BL/6 mouse is a useful model system in which to study the role of the CTL response in protective immunity to RSV. CTL lines and clones can mediate clearance of RSV from the lungs of normal mice without producing any associated morbidity.     

A mouse model for Niemann-Pick disease. Influence of genetic background on disease expression in spm/spm mice

Sphingomyelinosis (spm), an autosomal recessive mutation in mice originally occurred in the C57BL/KsJ inbred strain. Spm/spm mice of this genetic background show striking hepatosplenomegaly with a marked accumulation of sphingomyelin and cholesterol due to a deficiency of sphingomyelinase. However, in spm/spm mice of C57BL/6J and DBA/2J backgrounds, hepatosplenomegaly was not pronounced in spite of marked elevation of hepatic lipid concentrations. The lifespan of C57BL/6J-spm/spm and DBA/2J-spm/spm mice was shorter than that of C57BL/KsJ-spm/spm mice. This appeared to be associated with the comparatively rapid rise in hepatic lipid concentrations, which in turn might be related to the absence of hepatomegaly. Histological study revealed the formation of massive foam cell clusters in the livers and spleens of C57BL/KsJ-spm/spm mice, whereas in the case of C57BL/6J-spm/spm and DBA/2J-spm/spm mice, diffusely scattered foam cells were found. These findings suggest that the functions of reticuloendothelial system (RES) play a crucial role in the development of hepatosplenomegaly in response to lipid accumulation.     

Involvement of toll-like receptor 4 in innate immunity to respiratory syncytial virus

The mammalian Toll-like receptor 4, TLR4, is an important component in the innate immune response to gram-negative bacterial infection. The role of TLR4 in antiviral immunity has been largely unexplored. In this study, the in vivo immune responses to respiratory syncytial virus (RSV) and influenza virus infection were examined in TLR4-deficient (C57BL/10ScNCr) and TLR4-expressing (C57BL/10Sn) mice. TLR4-deficient mice challenged with RSV, but not influenza virus, exhibited impaired natural killer (NK) cell and CD14(+) cell pulmonary trafficking, deficient NK cell function, impaired interleukin-12 expression, and impaired virus clearance compared to mice expressing TLR4. These findings suggest that Toll signaling pathways have an important role in innate immunity to RSV.     

Acute colitis induced by dextran sulfate sodium progresses to chronicity in C57BL/6 but not in BALB/c mice: correlation between symptoms and inflammation

Exposure to dextran sulfate sodium (DSS) induces acute colitis, which is normally resolved after DSS removal. To study chronicity, mice are typically subjected to three to five cycles of weekly DSS exposures, each followed by a 1- to 2-wk rest period. Here, we describe a novel and convenient way of inducing chronic, progressive colitis by a single exposure to DSS. C57BL/6 mice exposed to DSS for 5 days developed acute colitis that progressed to severe chronic inflammation. The plasma haptoglobin levels remained high during the chronic phase, showing that the inflammation was active. Surprisingly, the mice regained their original weight along with the progression of colitis, and the only apparent symptom was loose feces. Histopathological changes 4 wk after DSS removal were dense infiltrates of mononuclear cells, irregular epithelial structure, and persistent deposits of collagen. A progressive production of the cytokines IL-1beta, IL-12 p70, and IL-17 correlated with the extensive cellular infiltration, whereas high IFN-gamma production was mainly found late in the chronic phase. Similar to C57BL/6 mice, BALB/c mice exposed to 5 days of DSS developed acute colitis as previously described. The acute colitis was accompanied by elevated plasma levels of haptoglobin and increased colonic levels of IL-1alpha/beta, IL-6, IL-18, and granulocyte colony-stimulating factor. However, soon after DSS removal, BALB/c mice recovered and were symptom free within 2 wk and completely recovered 4 wk after DSS removal in terms of histopathology, haptoglobin levels, and local cytokine production. In summary, these data stress the effect of genetic background on the outcome of DSS provocation. We believe that the present protocol to induce chronic colitis in C57BL/6 mice offers a robust model for validating future therapies for treatment of inflammatory bowel disease.     

Major histocompatibility complex-dependent cytotoxic T lymphocyte repertoire and functional avidity contribute to strain-specific disease susceptibility after murine respiratory syncytial virus infection

Susceptibility to respiratory syncytial virus (RSV) infection in mice is genetically determined. While RSV causes little pathology in C57BL/6 mice, pulmonary inflammation and weight loss occur in BALB/c mice. Using major histocompatibility complex (MHC)-congenic mice, we observed that the H-2(d) allele can partially transfer disease susceptibility to C57BL/6 mice. This was not explained by altered viral elimination or differences in the magnitude of the overall virus-specific cytotoxic T lymphocyte (CTL) response. However, H-2(d) mice showed a more focused response, with 70% of virus-specific CTL representing Vβ8.2(+) CTL directed against the immunodominant epitope M2-1 82, while in H-2(b) mice only 20% of antiviral CTL were Vβ9(+) CTL specific for the immunodominant epitope M187. The immunodominant H-2(d)-restricted CTL lysed target cells less efficiently than the immunodominant H-2(b) CTL, probably contributing to prolonged CTL stimulation and cytokine-mediated immunopathology. Accordingly, reduction of dominance of the M2-1 82-specific CTL population by introduction of an M187 response in the F1 generation of a C57BL/6N × C57BL/6-H-2(d) mating (C57BL/6-H-2(dxb) mice) attenuated disease. Moreover, disease in H-2(d) mice was less pronounced after infection with an RSV mutant failing to activate M2-1 82-specific CTL or after depletion of Vβ8.2(+) cells. These data illustrate how the MHC-determined diversity and functional avidity of CTL responses contribute to disease susceptibility after viral infection.     

Strain difference in expression of the adult-type polycystic kidney disease gene, pcy, in the mouse

DBA/2FG-pcy and C57BL/6FG-pcy congenic strains were established by transferring the polycystic kidney disease gene, pcy, to DBA/2 and C57BL/6 mice. We carried out pathological and hematological examinations of these strains at 4, 8, 16 and 30 weeks of age. In DBA/2FG-pcy mice more than 8 weeks of age, macroscopic renal cysts were observed on the surface of both kidneys. Their kidneys weight was significantly greater than in DBA/2 mice at all ages examined. Microscopic renal cysts were evenly distributed at 4, 8 and 16 weeks of age. At 30 weeks of age, the kidneys were filled with numerous polycysts. In C57BL/6FG-pcy mice, no macroscopic renal cysts were found until the animals were 30 weeks old, and the weight of their kidneys was greater than in B6 mice of the same age. From 8 weeks of age on, a limited number of microscopic renal cysts was observed, and many renal cysts were found adjacent to the enlarged Bowman's capsules. With age, the red blood cell count and hematocrit level decreased while the platelet count increased in both strains, with greater changes occurring in DBA/2FG-pcy mice than in C57 BL/6FG-pcy mice. These findings demonstrate that polycystic kidney disease exhibits strain differences in animals with a DBA/2 and C57BL/6 background. Our results suggest that phenotypic expression of the pcy gene in the mouse depends on genetic background, and that variations in the severity of human polycystic kidney disease may be explained, at least in part, by individual differences in genetic background.     

Tolerance to noninherited maternal MHC antigens in mice

The phenomenon of tolerance to noninherited maternal Ags (NIMA) is poorly understood. To analyze the NIMA effect C57BL/6 (H-2(b/b)) males were mated with B6D2F(1) (H-2(b/d)) females, whereby 50% of the offspring are H-2(b/b) mice that have been exposed to maternal H-2(d) alloantigens. Controls were H-2(b/b) offspring of C57BL/6 mothers, either inbred C57BL/6 mice or F(1) backcross mice from breedings with H-2(b/d) fathers. We found that 57% of the H-2(b/b) offspring of semiallogeneic (H-2(b/d)) mothers accepted fully allogeneic DBA/2 (H-2(d/d)) heart grafts for >180 days, while similar transplants were all rejected by day 11 in controls (p < 0.0004). Foster nursing studies showed that both oral and in utero exposure to NIMA are required for this tolerogenic effect. An effect of NIMA was also found to extend the survival of skin grafts from a semiallogeneic donor (p < 0.02). Pretransplant analysis of splenocytes showed a 40-90% reduction of IL-2-, IL-5-, and IFN-gamma-producing T cells responding to H-2(d)-expressing APC in NIMA(d)-exposed vs control mice. Injection of pregnant BALB/c-dm2 (H-2L(d)-negative) female mice i.v. with H-2L(d)(61-80) peptide profoundly suppressed the offspring's indirect pathway alloreactive CD4(+) T cell response to H-2L(d). These results suggest that the natural exposure of the fetus and newborn to maternal cells and/or soluble MHC Ags suppresses NIMA-allospecific T cells of the offspring, predisposing to organ transplant tolerance in adult mice.     

Major histocompatibility complex class II-regulated immunity to murine leukemia virus protects against early T- but not late B-cell lymphomas

We studied the relative importance of class I and class II major histocompatibility complex (MHC) immunoregulation in the control of T- and B-cell lymphomas induced by murine leukemia virus. Previously, we have described a mink cell focus-inducing (MCF) murine leukemia virus, MCF 1233, which induces not only lymphoblastic T-cell lymphomas but also follicle center cell or lymphoblastic B-cell lymphomas. We now report that the outcome of neonatal infection with MCF 1233 in H-2-congenic C57BL/10 and C57BL/6 mice is decisively influenced by the H-2 I-A locus. A total of 64% of H-2 I-Ak, d mice [B10.BR, B10.D2, B10.A(2R), B10.A(4R), and B10.MBR] developed T-cell lymphomas after MCF 1233 infection (mean latency, 37 weeks). In contrast, H-2 I-Ab [B10, B10.A(5R), B6], H-2 I-Ab/k [(B10.A x B10)F1 and (B10 x B10.A)F1], and H-2 I-Abm12 (bm12) mice were resistant against T-cell lymphomagenesis, but 65% of these H-2 I-Ab, b/k, bm12 animals developed B-cell lymphomas (mean latency, 71 weeks). Animals of T-cell lymphoma-susceptible strains that escaped from T-cell lymphomagenesis developed B-cell lymphomas with similar frequency as animals of T-cell lymphoma-resistant strains, but with a shorter latency. H-2 class II-determined regulation of antiviral immunity was reflected in the presence of high titers of antiviral envelope antibodies in T-cell lymphoma-resistant B-cell lymphoma-susceptible H-2 I-Ab, b/k, bm12 mice, whereas in T-cell lymphoma-susceptible H-2 I-Ak,d mice no antiviral antibodies were found. At week 4 after neonatal MCF 1233 infection, a high percentage of thymocytes were virally infected in both T-cell lymphoma-susceptible and -resistant mice. However, T-cell lymphoma-resistant animals cleared the thymic infection between weeks 4 and 10 of age, coinciding with a sharp rise in serum levels of antiviral antibodies. We conclude that the pleiotropic effects of MCF 1233 infection in H-2-congenic mice result from MHC class II I-A-determined T-cell response differences.     

Resistance to tolerance induction in B cells of autoimmune mice—Abnormal expansion of low affinity IgG-producing B-cell population

Several strains of mice are known to develop spontaneous autoimmune diseases like lupus erythematosus and they show various immunological abnormalities as well. Despite different genetic backgrounds, they manifest various immunological abnormalities in common, e.g., polyclonal B-cell activation (PBA) and resistance to tolerance induction. To elucidate mechanisms of the development of autoimmunity, tolerance inducibility was examined in autoimmune and normal mice using trinitrophenylated carboxymethyl cellulose (TNP-CMC) as tolerogen which is known to induce TNP-specific B-cell tolerance without the participation of T cells. NZB and MRL/Mp-lpr/lpr mice were used as autoimmune mice and C57BL/6, BALB/c, and MRL/Mp-+/+ mice as nonautoimmune mice. When TNP-CMC-injected mice were challenged with T-independent antigens, all of the mice tested were shown to be tolerant. In contrast, when TNP-CMC-injected mice were challenged with T-dependent antigen and secondary IgG responses were assessed, autoimmune mice showed rather hyperreactivity, while nonautoimmune mice showed hyporesponsiveness. Cyclophosphamide improved this defective tolerance inducibility. By the solid-phase radioimmunoassay it was revealed that average affinity of serum anti-TNP antibodies produced in TNP-CMC-injected mice was low. Such low affinity antibodies were produced in large amount in autoimmune mice. Hence, it was suggested that B-cell clones destined to produce low affinity IgG antibodies were responsible for the resistance to tolerance induction and such clones were expanding in autoimmune mice.     

Schistosoma mansoni: induction of severe glomerulonephritis in female BXSB mice following chronic infection

C57BL/6 (B6) and female BXSB mice were infected with 10 cercariae of Schistosoma mansoni per head in order to examine whether chronic parasite infection induced glomerulonephritis (GN) with polyclonal B-cell activation. Six months after the infection, mice were sacrificed and various immunological and histopathological examinations were performed. The following results were obtained. (1) Severe GN was induced in parasite-infected female BXSB mice. The renal changes were similar to those of male BXSB mice which spontaneously develop lupus-like GN. No substantial renal changes were observed in infected B6 mice. (2) Massive IgG and C3 deposits were found in capillary loops and also at the mesangial area of infected BXSB mice. No significant IC deposits were found in the kidney of infected B6 mice. (3) A high level of IC was detected in sera of some parasite-infected female BXSB mice, though no significant difference in the level of IC was found between infected and control mice. (4) Numbers of spleen IgG-producing cells were significantly increased in infected B6 mice. Infected female BXSB mice with splenomegaly showed higher numbers of IgGPC than uninfected mice, but there was no difference between the groups. These results suggest that genetic backgrounds played an important role in the development of lupus-like GN following the chronic infection of parasite-causing polyclonal B-cell activation.     

Streptobacillus moniliformis epizootic in barrier-maintained C57BL/6J mice and susceptibility to infection of different strains of mice

We report a Streptobacillus moniliformis epizootic in barrier-maintained SPF mice. Although various inbred and F1 hybrid strains of mice have been kept in this animal facility, only C57BL/6J Han [corrected] mice showed clinical signs of disease. During the course of the epizootic, 825 breeding animals (approximately 36% of the breeders) died or had to be killed because of severe clinical signs. Although sequential treatment with ampicillin and chlortetracycline gave good therapeutic results, the animal facility was vacated in order to exclude any risk of cross-contamination of the other rodent colonies in our institute. The source and route of transmission of S. moniliformis could not be elucidated. To investigate strain dependent differences experimental infection of different strains of mice with our S. moniliformis isolate was performed. After oral infection only C57BL/6J showed the typical signs of a cervical lymphadenitis and gave an immunological response. BALB/cJ, C3H/He, DBA/2J, CB6F1 and B6D2F1 mice were not affected except in two cases of DBA/2J and B6D2F1 mice where seroconversion was observed. After intravenous infection of C57BL/6J, DBA/2J [corrected] and BALB/cJ all animals showed positive titers in the indirect immunofluorescence test (IIF). One hundred percent of the C57BL/6J, forty percent of the DBA/2J, and none of the BALB/cJ mice developed severe symptoms. The results demonstrate that the susceptibility to streptobacillosis is predominantly influenced by genetic factors.     

Macroparasites at peripheral sites of infection are major and dynamic modifiers of systemic antimicrobial pattern recognition responses

Immune defences and the maintenance of immunological homeostasis in the face of pathogenic and commensal microbial exposures are channelled by innate antimicrobial pattern recognition receptors (PRRs) such as toll‐like receptors (TLRs). Whilst PRR‐mediated response programmes are the result of long‐term host‐pathogen or host–commensal co‐evolutionary dynamics involving microbes, an additional possibility is that macroparasitic co‐infections may be a significant modifier of such interactions. We demonstrate experimentally that macroparasites (the model gastrointestinal nematode, Heligmosomoides) at peripheral sites of infection cause substantial alteration of the expression and function of TLRs at a systemic level (in cultured splenocytes), predominantly up‐regulating TLR2, TLR4 and TLR9‐mediated cytokine responses at times of high standing worm burdens. We consistently observed such effects in BALB/c and C57BL/6 mice under single‐pulse and trickle exposures to Heligmosomoides larvae and in SWR and CBA mice under single‐pulse exposures. A complementary long‐term survey of TLR2‐mediated tumour necrosis factor‐alpha responses in wild wood mice (Apodemus sylvaticus) was consistent with substantial effects of macroparasites under some environmental conditions. A general pattern, though, was for the associations of macroparasites with TLR function to be temporally dynamic and context‐dependent: varying with different conditions of infection exposure in the field and laboratory and with host genetic strain in the laboratory. These results are compelling evidence that macroparasites are a major and dynamic modifier of systemic innate antimicrobial responsiveness in naturally occurring mammals and thus likely to be an important influence on the interaction between microbial exposures and the immune system.     

Role of mink cell focus-inducing virus in leukemias induced by Friend ecotropic virus

Recombinant viruses have been implicated in the pathogenesis of murine leukemias induced by a variety of long-latency retroviruses. Neonatal mice of several strains were inoculated with Friend ecotropic virus (F-Eco) and analyzed for the presence of mink cell focus-inducing (MCF) virus or DNA restriction enzyme fragments which were specific for Friend MCF virus (F-MCF). MCF virus was detected within 2 weeks of inoculation in NFS /N mice and at about 2 months after inoculation in BALB/c mice. Both of these strains developed erythroblastosis after inoculation with F-Eco. In contrast, MCF virus was not detected in F-Eco-inoculated C57BL mice. These mice were resistant to erythroblastosis but developed lymphoma or myelogenous leukemia or both at about 5 months after inoculation. Thus, although MCF viruses were associated with F-Eco erythroblastosis in NFS /N and BALB/c mice, they were not necessary for F-Eco-induced lymphoid or myeloid leukemias in C57BL mice. To investigate the association between resistance to erythroblastosis and absence of MCF virus, C57BL mice were inoculated with pseudotypic mixtures of F-Eco plus F-MCF; MCF virus replicated well in these mice, but the mice remained resistant to erythroblastosis. Furthermore, in genetic crosses between C57BL and NFS /N or BALB/c, some mice inherited resistance to F-Eco erythroblastosis without inheriting the C57BL resistance to the generation of MCF viruses. These results indicate that C57BL mice carry a gene for resistance to F-Eco erythroblastosis which is distinct from the C57BL genes which interfere with the generation of MCF viruses.     

Characterization of single nucleotide polymorphisms for a forward genetics approach using genetic crosses in C57BL/6 and BALB/c substrains of mice

Forward genetics is a powerful approach based on chromosomal mapping of phenotypes and has successfully led to the discovery of many mouse mutations in genes responsible for various phenotypes. Although crossing between genetically remote strains can produce F₂ and backcross mice for chromosomal mapping, the phenotypes are often affected by background effects from the partner strains in genetic crosses. Genetic crosses between substrains might be useful in genetic mapping to avoid genetic background effects. In this study, we investigated single nucleotide polymorphisms (SNPs) available for genetic mapping using substrains of C57BL/6 and BALB/c mice. In C57BL/6 mice, 114 SNP markers were developed and assigned to locations on all chromosomes for full utilization for genetic mapping using genetic crosses between the C57BL/6J and C57BL/6N substrains. Moreover, genetic differences were identified in the 114 SNP markers among the seven C57BL/6 substrains from five production breeders. In addition, 106 SNPs were detected on all chromosomes of BALB/cAJcl and BALB/cByJJcl substrains. These SNPs could be used for genotyping in BALB/cJ, BALB/cAJcl, BALB/cAnNCrlCrlj, and BALB/cCrSlc mice, and they are particularly useful for genetic mapping using crosses between BALB/cByJJcl and other BALB/c substrains. The SNPs characterized in this study can be utilized for genetic mapping to identify the causative mutations of the phenotypes induced by N-ethyl-N-nitrosourea mutagenesis and the SNPs responsible for phenotypic differences between the substrains of C57BL/6 and BALB/c mice.     

C57BL/6J-bgJ (beige) mice: differential sensitivity in the tail flick test to centrally administered mu- and delta-opioid receptor agonists

The antinociceptive effects of two mu-opioid receptor agonists, morphine and [D-Ala2, MePhe4, Gly-ol5]enkephalin (DAGO), and a selective delta-receptor agonist, [D-Pen2, L-Pen5]enkephalin (DPLPE), were determined in C57BL/6J-bgJ (beige) and control mice (CRS-CDl and C57BL/6By) using a standard tail-flick assay. The antinociceptive response of C57BL/6J-bgJ mice to intracerebro-ventricularly administered morphine and DAGO was significantly reduced compared to controls, but there was no difference in the antinociceptive response to DPLPE. These results suggest that there is a genetic deficit of mu-opioid receptor number or a genetically-induced alteration in receptor function in regions of C57BL/6J-bgJ brains involved in antinociception, that delta-opioid receptors can mediate antinociception in mice, and that the C57BL/6J-bgJ strain may offer a practical new animal model for studying the function of opioid receptor subtypes.     

Intranasal Administration of Antibody-Bound Respiratory Syncytial Virus Particles Efficiently Primes Virus-Specific Immune Responses in Mice

Infants are protected from a severe respiratory syncytial virus (RSV) infection in the first months of life by maternal antibodies or by prophylactically administered neutralizing antibodies. Efforts are under way to produce RSV-specific antibodies with increased neutralizing capacity compared to the currently licensed palivizumab. While clearly beneficial during primary infections, preexisting antibodies might affect the onset of adaptive immune responses and the ability to resist subsequent RSV infections. Therefore, we addressed the question of how virus neutralizing antibodies influence the priming of subsequent adaptive immune responses. To test a possible role of the neonatal Fc receptor (FcRn) in this process, we compared the responses in C57BL/6 wild-type (WT) and FcRn^−/− mice. We observed substantial virus-specific T-cell priming and B-cell responses in mice primed with RSV IgG immune complexes resulting in predominantly Th1-type CD4⁺ T-cell and IgG2c antibody responses upon live-virus challenge. RSV-specific CD8⁺ T cells were primed as well. Activation of these adaptive immune responses was independent of FcRn. Thus, neutralizing antibodies that localize to the airways and prevent infection-related routes of antigen processing can still facilitate antigen presentation of neutralized virus particles and initiate adaptive immune responses against RSV.     

Characterization of effector cells of graft vs leukemia following allogeneic bone marrow transplantation in mice inoculated with murine B-cell leukemia

Summary It is now widely accepted that immunocompetent lymphocytes in allogeneic bone marrow grafts exert an antileukemic effect that contributes to the cure of leukemia. Graft vs leukemia (GVL) effects independent of graft vs host disease were investigated in allogeneic bone marrow chimeras tolerant of host and donor alloantigens. The role of Thy1.2, L3T4 and Lyt2 T lymphocytes as effector cells of GVL were investigated in (BALB/c × C57BL/6)F1 mice inoculated with murine B-cell leukemia and subsequently conditioned with total lymphoid irradiation and cyclophosphamide (200 mg/kg). Mice were reconstituted with C57BL/6 bone marrow cells depleted of well-defined T-cell subsets or enriched for stem cells by the soybean agglutination method. Detection of residual tumor cells, an indicator for efficacy of GVL, was carried out by adoptive transfer of peripheral blood or spleen cells obtained from treated chimeras into secondary naive BALB/c recipients at different time intervals following bone marrow transplantation. Treatment of the primary marrow inoculum with monoclonal anti-Thy 1.2 or anti-Lyt2 abolished the GVL effects and all secondary BALB/c recipients developed leukemia within 60 days. On the other hand, the treatment with monoclonal anti-L3T4 did not influence the effect of GVL and all treated recipients remained without leukemia. The data suggest that T cells may mediate GVL effects in the absence of graft vs host disease and in circumstances where tolerance to conventional alloantigens is elicited. Effector cells of GVL across the major histocompatibility complex (MHC) in the murine B-cell leukemia tumor model system appear to be Thy 1.2⁺ Lyt2⁺ L3T4—. Induction of GVL effects by allogeneic cells tolerant of host MHC suggests that these effects may be independent of graft vs host disease.