Behavioral characterization of A/J and C57BL/6J mice using a multidimensional test: association between blood plasma and brain magnesium-ion concentration with anxiety.

Up to 29% of all adults will experience an anxiety-related disorder during their lives. Treatment of these disorders is still difficult and the exact mechanisms and pathways behind anxiety disorders remain to be elucidated. Although evidence exists for genetically based susceptibility of human psychiatric diseases, risk genes have rarely been identified up to now. Inbred mouse strains are, together with the crosses and genetic reference populations derived from them, important tools for the genetic dissection of complex behavioral traits in the mouse. Thus, inbred mouse models of human anxiety may be a potent starting tool to search for candidate genes in mice, which could then via comparative genomics be translated to the human situation. In this paper we investigate whether the A/J and C57BL/6J mouse inbred strains differ in a limited number of motivational systems (anxiety, exploration, memory, locomotion, and social affinity), but especially in anxiety-related behavior from each other. Young adult individuals from both genders of A/J and C57BL/6J strains were behaviorally phenotyped using a multidimensional test: the modified hole board. This paradigm basically is a combination of the traditional hole board and the open field test allowing to test for anxiety-related avoidance behavior, risk assessment, arousal, exploration, memory, locomotor activity, and social affinity, using just one single test. An acute, aversive stimulus (intra-peritoneal injection with saline) was applied to the animals to test for the robustness of their behavioral phenotype. In addition, presumed physiological indicators for anxiety (circulating glucose, cholesterol, and corticosterone, adrenal tyrosine hydroxylase, and blood plasma and brain magnesium) were investigated. It could be concluded that C57BL/6J and A/J mice differ with respect to almost all tested motivational systems. For some measures, including anxiety-related behavioral parameters, there were clear gender effects. The high-anxiety phenotype of A/J mice could be shown to represent a primary and robust characteristic. Further, blood plasma and brain magnesium levels were significantly correlated with several anxiety-related behavioral parameters. These results emphasize the hypothesized, and possibly causal, association between magnesium status and emotionality.

Vanadium pentoxide induces pulmonary inflammation and tumor promotion in a strain-dependent manner.

BACKGROUND: Elevated levels of air pollution are associated with increased risk of lung cancer. Particulate matter (PM) contains transition metals that may potentiate neoplastic development through the induction of oxidative stress and inflammation, a lung cancer risk factor. Vanadium pentoxide (V2O5) is a component of PM derived from fuel combustion as well as a source of occupational exposure in humans. In the current investigation we examined the influence of genetic background on susceptibility to V2O5-induced inflammation and evaluated whether V2O5 functions as a tumor promoter using a 2-stage (initiation-promotion) model of pulmonary neoplasia in mice. RESULTS: A/J, BALB/cJ (BALB), and C57BL/6J (B6) mice were treated either with the initiator 3-methylcholanthrene (MCA; 10 microg/g; i.p.) or corn oil followed by 5 weekly aspirations of V2O5 or PBS and pulmonary tumors were enumerated 20 weeks following MCA treatment. Susceptibility to V2O5-induced pulmonary inflammation was assessed in bronchoalveolar lavage fluid (BALF), and chemokines, transcription factor activity, and MAPK signaling were quantified in lung homogenates. We found that treatment of animals with MCA followed by V2O5 promoted lung tumors in both A/J (10.3 +/- 0.9 tumors/mouse) and BALB (2.2 +/- 0.36) mice significantly above that observed with MCA/PBS or V2O5 alone (P < 0.05). No tumors were observed in the B6 mice in any of the experimental groups. Mice sensitive to tumor promotion by V2O5 were also found to be more susceptible to V2O5-induced pulmonary inflammation and hyperpermeability (A/J>BALB>B6). Differential strain responses in inflammation were positively associated with elevated levels of the chemokines KC and MCP-1, higher NFkappaB and c-Fos binding activity, as well as sustained ERK1/2 activation in lung tissue. CONCLUSIONS: In this study we demonstrate that V2O5, an occupational and environmentally relevant metal oxide, functions as an in vivo lung tumor promoter among different inbred strains of mice. Further, we identified a positive relationship between tumor promotion and susceptibility to V2O5-induced pulmonary inflammation. These findings suggest that repeated exposures to V2O5 containing particles may augment lung carcinogenesis in susceptible individuals through oxidative stress mediated pathways.

Fine mapping and identification of candidate pulmonary adenoma susceptibility 1 genes using advanced intercross lines.

In the present study, we used newly developed F(11) generation mouse advanced intercross lines (AIL) to fine map Pas1-3 quantitative trait loci (QTL). The (A/J x C57BL/6) F(11) AIL mouse population was created by crossing lung tumor-resistant C57BL/6 mice with lung tumor-susceptible A/J mice. By selectively genotyping 30% of the population, we have confirmed the Pas1 QTL and narrowed it to an interval of approximately 1.0 cM or 1.3 Mb in the vicinity of the Kras2 gene. The Pas2 QTL was detected by both ANOVA and regression analysis but not by MapMaker EXP/QTL software. In addition, an interaction between the Pas1 and Pas2 QTLs was revealed. However, the Pas3 QTL was not confirmed in this study. It was either lost during the development of the AIL or too weak to be detected using AIL. The Pas1 locus is now sufficiently fine-mapped that candidate gene(s) for the Pas1 locus can be characterized by positional cloning. In this study, all 27 of the known or predicted genes located in the Pas1 candidate region were characterized as possible candidate Pas genes. Six genes were selected for additional analyses because of their relevant function in tumorigenesis or allelic changes between A/J and C57BL/6 mice. The Lrmp gene bears amino acid polymorphisms among various mouse strains that are highly correlated with the Pas1 allele status. The Pas1c1 gene (RIKEN Ak016641), encoding an intermediate filament tail domain-containing protein, produces alternatively spliced transcripts across inbred strains of mice, and its splicing pattern cosegregates with the Pas1 allele. The genetic and expression data support these two genes as strong candidates for the Pas1 locus. Of the other four genes (Eca39, RIKEN Ak015530, mHoj-1, and Krag), no functional polymorphisms or differential gene expression were found in Eca39, mHoj-1, and Krag between lung tumor-susceptible and -resistant strains. The Ak015530 carries an amino acid polymorphism, but this polymorphism does not cosegregate with mouse lung tumor susceptibility. Thus, these 4 genes are less likely candidates for the Pas1 locus.

The genotype of mice influences the autoimmune response to spliceosome proteins induced by cytomegalovirus gB immunization.

In previous studies we have established a link between cytomegalovirus (CMV) infection and an autoimmune response to the U1-70 k protein of the spliceosome in man. This autoimmune response, generally referred to as the anti-RNP (ribonucleoprotein) antibodies, is observed in about 30% of patients with systemic lupus erythematosus (SLE). We have also found that the CMV glycoprotein B (CMV gB) when expressed in a adenovirus vector (Ad) could induce a significant anti-U1-70 k antibody response in several strains of mice, such as C3H, MRL and BALB/c. In the present study we examined the autoimmune response induced by immunization with Ad-gB in A/J and C57BL/6 (B6) mice and determined whether there was any autoimmune phenotype similar to that observed in patients with SLE. Thus groups of A/J and B6 mice were immunized with Ad/gB or with Ad alone and then observed for possible skin or kidney disease. In addition the autoantibody response to the spliceosome was measured, and the target antigens identified by immunoblot techniques. All of the A/J mice mounted a very high IgG response primarily to the U1-70 k protein of the spliceosome, with evidence of a rapid spreading of the autoantibody response to other components of the complex. In contrast, B6 mice mounted only a very low titre autoantibody response and failed to show signs or symptoms of autoimmunity. The A/J but not the B6 mice were found to have deposits of IgG in their kidneys, which were consistent with abnormal levels of blood urea nitrogen in the A/J but not B6 mice. This study demonstrates the importance of the genetic background in the susceptibility to autoimmunity.

Comparative analysis of mycobacterial infections in susceptible I/St and resistant A/Sn inbred mice.

SETTING: The availability and appropriate use of animal models is of significant importance for a better and more detailed understanding of the genetic, immunological and pathological mechanisms underlying the development of mycobacterial disease in humans. OBJECTIVE: To define a mouse model for tuberculosis severity that can be easily adapted to genetic and immunological analysis of host response to Mycobacterium tuberculosis infection. DESIGN: We describe here two inbred strains of mice, I/St and A/Sn (both Nramp1'), that differ vastly in commonly used parameters of susceptibility to infection with virulent and attenuated strains of M. tuberculosis. RESULTS: Following infection with a high dose of virulent H37Rv. M. tuberculosis and compared to their resistant A/Sn counterparts, I/St mice displayed more than a 2-fold shorter mean survival time and a more rapid onset and progression of severe body weight loss (cachexia). Moreover, I/St mice supported 20-100-fold higher multiplication of M. tuberculosis following challenge with H37Rv over a large range of infectious inocula. The high susceptibility of I/St mice was also reflected by more severe lung histopathology as evidenced by larger and more numerous lung granuloma and macrophage dominated cellular infiltrates. Finally, we determined that I/St are also unable to control infection with attenuated H37Ra M. tuberculosis and two strains of M. bovis (BCG and Ravenel) indicating hyper-susceptibility of the I/St mouse strain to mycobacterial infections. CONCLUSIONS: The results of our experiments suggest that comparative analysis of resistant A/Sn and susceptible I/St mice provides an ideal way to study host dependent aspects of tuberculosis susceptibility under the controlled conditions provided by an animal model.

Increased glycogen synthase kinase-3 activity in diabetes- and obesity-prone C57BL/6J mice.

Although the precise mechanisms contributing to insulin resistance and type 2 diabetes are unknown, it is believed that defects in downstream components of the insulin signaling pathway may be involved. In this work, we hypothesize that a serine/threonine kinase, glycogen synthase kinase-3 (GSK-3), may be pertinent in this regard. To test this hypothesis, we examined GSK-3 activity in two inbred mouse strains known to be susceptible (C57BL/6J) or resistant (A/J) to diet-induced obesity and diabetes. Examination of GSK-3 in fat, liver, and muscle tissues of C57BL/6J mice revealed that GSK-3 activity increased twofold in the epididymal fat tissue and remained unchanged in muscle and liver of mice fed a high-fat diet, compared with their low-fat diet-fed counterparts. In contrast, GSK-3 activity did not change in the epididymal fat tissue of A/J mice, regardless of the type of diet they were fed. In addition, both basal and diet-induced GSK-3 activity was higher (2.3- and 3.2-fold, respectively) in the adipose tissue of C57BL/6J mice compared with that in A/J mice. Taken together, our studies suggest an unsuspected link between increased GSK-3 activity and development of insulin resistance and type 2 diabetes in fat tissue of C57BL/6J mice, and implicate GSK-3 as a potential factor contributing to susceptibility of C57BL/6J mice to diet-induced diabetes.

The role of motor activity in diet-induced obesity in C57BL/6J mice.

Previous research in our laboratory has demonstrated that the C57BL/6J (B/6J) mouse has a predisposition to develop severe obesity if placed on a high-fat diet. In the present study we assessed the role of physical activity in this phenomenon. Obesity-prone B/6J and obesity-resistant A/J mice were placed on one of four diets; high fat/high sucrose, high fat/low sucrose, low fat/high sucrose, and low fat/low sucrose. After 4 months, all animals on the high-fat diets had gained more weight than animals on the low-fat diets, and this phenomenon was greatly exaggerated in B/6J mice. Despite the fact that B/6J mice gained more weight than A/J mice on high-fat diets without consuming more calories, spontaneous motor activity was elevated in B/6J mice compared to A/J mice. There was no effect of the diets on activity either within or across strains. These data suggest that predisposition to diet-induced obesity is not explainable by reduced levels of physical activity.

Genetic basis of hypo-responsiveness of A/J mice to interleukin-3.

Hematopoietic progenitor cells of the A/J strain of mice show a pronounced defect in the ability to form colonies or proliferate in response to interleukin-3 (IL-3). Comparison of immunoblots of A/J mast cells and of mast cells from the C57BL/6 strain that respond normally to IL-3 showed that, in both strains, a 125-kD band of the expected size was recognized by an antibody against the beta chain of the IL-3 receptor, the AIC2A molecule. However, in the C57BL/6 cells, there was an additional 110-kD species not seen in cells of the A/J strain. Analyses using bone marrow-derived mast cells from a panel of A/J x C57BL/6 and A/J x C57BL/6 recombinant inbred (RI) mice showed that the hypo-responsiveness to IL-3 is governed by a single gene. However, the absence of this 110-kD species in the A/J strain did not co-map with IL-3 hypo-responsiveness but did indeed map to the AIC2A genetic locus. These data show that this trait in the A/J strain was due to a polymorphism of the AIC2A gene unrelated to IL-3 hypo-responsiveness. Typing of the RI strains for the markers D14Mit98, D14Mitl4, and D14Mit133 mapped the locus determining hypo-responsiveness to IL-3 to the subtelomeric region of chromosome 14, the region that also bears the gene encoding the alpha chain of the IL-3 receptor (lL-3Ralpha). Immunofluorescence analyses indicated that IL-3Ralpha protein was undetectable on fresh bone marrow cells from A/J mice, although clearly detectable on cells from the responder C57BL/6 strain. However, IL-3Ralpha was readily detectable at normal levels on A/J mast cells generated by culture of A/J bone marrow cells in a combination of IL-3 and steel factor. Moreover, IL-3Ralpha on these A/J mast cells appears to be functional in that IL-3 stimulation of these cells results in tyrosine phosphorylation events characteristic of IL-3 signaling, including tyrosine phosphorylation of the beta chain of the IL-3 receptor, Jak-2 kinase, and SHPTP2. Collectively, these data indicate that the hypo-responsiveness of A/J mice to IL-3 is due to a defect in the gene encoding IL-3Ralpha and that, although this defect gives rise to reduced expression of alpha chain on primary bone marrow cells, this defect is not absolute and that, under certain circumstances, A/J cells can express functional receptors.

Molecular genetic characterization of the senescence-accelerated mouse (SAM) strains.

Senescence-Accelerated Mouse (SAM) is a murine model of accelerated senescence, which consists of the senescence-prone P series and the senescence-resistant R series of strains. In order to characterize these SAM strains molecular genetically, we have performed a series of Southern hybridization experiments using oligonucleotide probes designed to recognize the endogenous mouse retrovirus sequences. The repertoires of endogenous retroviruses in different SAM strains indicated that each SAM strain is distinct. Comparisons of the SAM strains with the parental AKR/J strain revealed significant differences between them, suggesting the involvement of other strains in the course of the development of SAM. While some of the endogenous retroviruses were found in all of the SAM strains, others were found to be distributed uniquely, indicating their potential usefulness as genetic markers in the analysis of strain-specific phenotypes, and possibly of the phenomenon of accelerated senescence itself.

Ontogeny of tolerogen-responsive lymphocytes following neonatal inoculation of class II disparate semiallogeneic cells.

Spleens of adult mice of the A strain background that were rendered tolerant as neonates of class II alloantigens only (A.TH tolerant of A.TL, A.TL tolerant of A.TH) contain large numbers of tolerogen-responsive T cells, many of which secrete IL-4, but not IL-2. Since these spleens also contain suppressor cells that can adoptively transfer skin allograft acceptance in vivo and can prevent generation of class II-specific cytotoxic T cells in vitro, it is important to determine the origins during postnatal development of these cells. Class II disparate, semiallogeneic haematopoietic cells were injected into newborn A.TH and A.TL mice. Periodically thereafter (1 to 60 days post-injection, but prior to challenge with a tolerogen-bearing skin graft), thymocytes and splenocytes from these mice were examined in vitro for tolerogen-specific reactivity in mixed lymphocyte reactions during which proliferation and IL-2 and IL-4 production were assayed. Within 24 hours of neonatal injection, the thymus and spleens of injected mice were profoundly depleted of tolerogen-responsive T cells. However, there was no commensurate loss of I-E-related V beta 5+ cells in the thymus of A.TH mice that received neonatal inoculations of I-E-bearing A.TL cells. During the ensuing weeks, tolerogen-responsive proliferative and IL-4-secreting T cells were detected in thymus and spleen. However, not until after the mice were more than 60 days of age were tolerogen-responsive cells able to secrete IL-2. Since physical clonal deletion of tolerogen-related V beta 5+ cells is a characteristic of neither neonatal nor adult A.TH and A.TL mice that received injections of semiallogeneic cells at birth, and since tolerogen-responsive IL-4 producing cells exist in adult mice that have permanently accepted (A.TH x A.TL)F1 skin grafts, our results imply that the tolerogen-responsive T cells detected in adult tolerant mice are descendants of the novel IL-4-producing T cells that arise in the thymus almost immediately after the tolerance conferring inoculum of semiallogeneic cells. The possible mechanisms responsible for generation of IL-4-producing, tolerogen-responsive T cells and the role of these cells in maintenance of tolerance of class II alloantigens are discussed.

The AXB and BXA set of recombinant inbred mouse strains.

The recombinant inbred (RI) set of strains, AXB and BXA, derived from C57BL/6J and A/J, originally constructed and maintained at the University of California/San Diego, have been imported into The Jackson Laboratory and are now in the 29th to 59th generation of brother-sister matings. Genetic quality control testing with 45 proviral and 11 biochemical markers previously typed in this RI set indicated that five strains had been genetically contaminated sometime in the past, so these strains have been discarded. The correct and complete strain distribution patterns for 56 genetic markers are reported for the remaining RI strain set, which consists of 31 living strains and 8 extinct strains for which DNA is available. Two additional strains, AXB 12 and BXA 17, are living and may be added to the set pending further tests of genetic purity. The progenitors of this RI set differ in susceptibility to 27 infectious diseases as well as atherosclerosis, obesity, diabetes, cancer, cleft palate, and hydrocephalus. Thus, the AXB and BXA set of RI strains will be useful in the genetic analysis of several complex diseases.

Genotype influences the development of tolerance to nicotine in the mouse.

Previous studies have demonstrated that chronic infusion of DBA/2 inbred mice with nicotine results in a dose- and time-dependent tolerance to many of the effects elicited by a challenge dose of nicotine. This tolerance was paralleled by increases in the number of brain nicotinic receptors measured with L-[3H]nicotine and alpha-[125I]bungarotoxin binding, suggesting that receptor up-regulation may underlie tolerance to nicotine. The studies reported here assessed the development of tolerance to nicotine in five inbred mouse strains that differ markedly in sensitivity to acute doses of nicotine. Mice were infused with nicotine doses ranging between 0 and 6 mg/kg/hr for 10 days and were tested for sensitivity to nicotine using several tests 2 hr after infusion was stopped. Some mouse strains, such as the C57BL/6, developed tolerance to nicotine, as measured by shifts to the right of dose-response curves, at the lowest infusion doses, whereas other strains, such as the C3H/2 and BUB, did not develop measurable tolerance until the highest infusion doses were used. A correlation between sensitivity to acute nicotine treatment and the threshold for tolerance development was observed, suggesting that tolerance develops only after a physiological effect is elicited. All of the mouse strains exhibited a dose-dependent increase in nicotine binding in all brain regions; no marked strain differences were seen in up-regulation of this binding site. Chronic nicotine infusion also evoked increases in alpha-bungarotoxin binding, but higher doses were required to elicit this effect. Changes in this binding site were observed after treatment with nicotine doses that elicited tolerance in those mouse strains that are more resistant to an acute dose of nicotine. These results indicate that the relationship between tolerance development and brain nicotinic receptor up-regulation may not be simple.

Intracellular destruction of salmonellae in genetically resistant mice.

Virulent Salmonella typhimurium, 2000 LD50, were injected intraperitoneally into inbred male A/J mice, genetically resistant to salmonella infection. Peritoneal exudate cells were harvested between 5 and 54 h after infection and examined by electronmicroscopy. Polymorphs were seen ingesting as well as digesting the pathogens as early as 5 h after infection. Macrophages were equally active in destroying the phagocytosed organisms throughout this period. In the meantime, the proliferation of salmonellae appeared to occur extracellularly in the peritoneal cavity as evidenced by their division.

Genetic differences in plasma corticosterone levels in response to nicotine injection.

Changes in plasma corticosterone (CCS) levels following intraperitoneal injections of nicotine were measured in four inbred mouse strains: DBA/2Ibg, C57BL/6Ibg, C3H/2Ibg, and A/J. In all four strains, nicotine produced a dose-dependent (0.5-2.0 mg/kg nicotine) increase in plasma CCS levels which peaked 10-30 min after injection. Saline increased plasma CCS levels in C57BL, A, and C3H, but not in DBA mice. After correcting for plasma CCS levels produced by saline injection, the nicotine-induced rise in plasma CCS was significantly lower for the C57BL strain than for the other three strains tested. These mouse strains also varied in their responses to saline injection with the rank order: C57BL greater than A = C3H greater than DBA. However, the two most divergent strains (C57BL and DBA) did not differ in the effects of a cold water stress. The response to nicotine was completely inhibited by mecamylamine in two strains tested (C3H and C57BL) whereas the response to saline injection was unaffected, suggesting that only the response to nicotine was mediated by nicotinic receptors. It is clear that elevations in plasma CCS induced either by saline injection or by nicotine are influenced by genetic factors.

Influence of genotype on nicotine-induced increases of plasma corticosterone in mice as a result of acute nicotine pretreatment.

Acute exposure to nicotine produces an elevation of plasma corticosterone levels in rodents. The consequences of repeated exposure to nicotine administered intraperitoneally (IP) were examined in three inbred strains of mice, DBA/2Ibg, C3H/2Ibg and A/J. These strains of mice have been shown previously to differ in a variety of behavioral and physiological responses to acute nicotine exposure. Mice were administered saline or 1.00 mg/kg nicotine IP, followed 30 min later by a range of nicotine doses (0.25-1.00 mg/kg). Strain differences were observed for the dose-response to the second injection; however, no effect of acute nicotine pretreatment was demonstrated. The observed lack of desensitization was consistent across genotype. An intragastric administration of a pretreatment dose of nicotine (4.00 mg/kg) also failed to produce desensitization to a subsequent IP nicotine injection in any strain. Increasing the time interval between injections to 45 min did not alter the CCS response. However, at 90 min between injections, a supersensitive CCS response was measured in all strains.

On the active site of liver acetyl-CoA. Arylamine N-acetyltransferase from rapid acetylator rabbits (III/J).

A covalent, catalytic intermediate of cytosolic liver acetyl coenzyme A: arylamine N-acetyltransferase (EC 2.3.1.5) from rapid acetylator rabbits (III/J) was isolated and chemically characterized. The active site was further studied using two covalent inhibitors, [2-3H]iodoacetic acid and bromoacetanilide. Inhibition experiments with [2-3H]iodoacetic acid at pH 6.9 showed that the incorporation of 0.7 mol of [2-3H]iodoacetic acid/mol of N-acetyltransferase led to rapid, irreversible loss of enzyme activity. Preincubation of the enzyme with acetyl coenzyme A (acetyl-CoA) completely protected against inactivation by [2-3H]iodoacetic acid. After incubating the N-acetyltransferase with [2-3H]acetyl-CoA in the absence of an acceptor amine, an acetyl-cysteinyl-enzyme intermediate was isolated and characterized. Preincubation of N-acetyltransferase with iodoacetic acid prevented the incorporation of the [2-3H]acetyl group into the enzyme. The product analog, bromoacetanilide, caused a rapid irreversible loss of N-acetyltransferase activity. The reaction was pseudo first-order and saturated at high bromoacetanilide concentrations (KI = 0.67 mM; k3 = 1 min-1). Preincubation of the enzyme with acetyl-CoA prevented inactivation by the inhibitor. The acceptor amine 4-ethylaniline did not prevent inhibition. Incorporation of the inhibitor was directly proportional to the loss of activity showing a 1:1 stoichiometry of enzyme to inhibitor. The target amino acid was identified as cysteine by amino acid analysis of inhibitor-treated enzyme.

Genetic regulation of lipopolysaccharide-induced interleukin 1 production by murine peritoneal macrophages.

The production of IL 1 by LPS-stimulated peritoneal macrophages from inbred mouse strains was studied. Macrophages from A/J (A) mice were deficient in IL 1 production, when compared with high IL 1-producing strains, including C57BL/6J (B). The difference between A and B macrophages was maintained over a wide LPS concentration range and throughout a 72-hr incubation period. Because of these differences, it was possible to investigate the mechanisms regulating IL 1 production by applying techniques of genetic analysis by using recombinant inbred (RI) strains derived from the A and B progenitors. A strain distribution pattern (SDP) of IL 1 production (low/high response) was obtained with the use of 15 AXB/BXA RI strains. This suggested the presence of a major gene locus controlling the production of IL 1 in response to LPS stimulation, with allelic differences presumably resulting in deficient or efficient IL 1 production. In addition, there appeared to be one or more other loci involved in determining the magnitude of the IL 1 response to LPS in the responder mice. The IL 1 response did not appear to be linked to the major histocompatibility complex, since B10.A mice (which share the same H-2a haplotype as A/J) were efficient IL 1 producers. There did not appear to be any correlation between the degree of IL 1 production and the magnitude of the peritoneal macrophage inflammatory response, or between IL 1 production and LPS responsiveness (as determined by splenocyte proliferation). SDP analysis also indicated that the IL 1 response was not linked to macrophage tumoricidal activity. A comparison of the SDP for IL 1 production with a library of SDP for other known genetic waits suggested linkage with at least four loci on chromosome 1.

Elevated myc expression and c-myc amplification in spontaneously occurring B lymphoid cell lines.

Recently, a minor subpopulation of murine B lymphocytes, Ly-1+ B cells, has been distinguished by its unique ontogeny, tissue distribution, and prominence in certain autoimmune and neoplastic B cell diseases. We have previously described a simple murine spleen culture system that results in the spontaneous and exclusive outgrowth of long-term Ly-1+ B cell lines (B Ly-1 cells). Here, we report that the immortal growth property of B Ly-1 cells correlates with a 10-45-fold elevation of steady-state myc RNA and 2-10-fold amplification of the c-myc locus. While c-myc amplification has been observed in malignant cell lines derived from several tissues of origin, its occurrence in lymphoid cells has not been previously reported. The consistent c-myc amplification in B Ly-1 cells may reflect a unique state of this locus in the Ly-1+ B lymphocyte lineage, and contribute to the spontaneous immortalization of this B cell population in vitro, and its apparent predilection for malignant transformation in vivo.

Previous immunization of mice with herpes simplex virus type-1 strain MP protects against secondary corneal infection.

Herpes simplex virus (HSV)-induced ocular disease is occurring in epidemic proportions throughout the world, and is the number one cause of unilateral corneal blindness in all developed countries. We have found, in a mouse model of herpes simplex keratitis (HSK), that products encoded by the Igh-1 locus on chromosome 12 exert a profound influence on the immune/inflammatory response in the cornea after HSV inoculation in the cornea. Thus, mice with Igh-1c or Igh-1d phenotype routinely develop extreme keratopathy and loss of corneal clarity after HSV encounter in the eye, while congenic strains expressing other Igh-1 phenotypes develop substantially less keratopathy. We examined the effect of previous subcutaneous immunization with the mutant, less virulent, MP strain of HSV on the development of keratitis and encephalitis after secondary corneal inoculation with strains MP, mP, F, and KOS. A/J mice (Igh-1c), 5-6 weeks old, were injected sc with live HSV-1 strain MP. Controls were injected with culture media without virus. Three weeks later both immunized and control nonimmunized animals were challenged in the cornea with HSV-1, strains MP, mP, F, and KOS. The animals were clinically scored for keratitis and encephalitis at regular intervals for 21 days following corneal challenge. None of the immunized animals challenged in the cornea with strain MP, 5 X 10(4) plaque-forming units (PFU), developed clinical signs of encephalitis compared to 86% of unimmunized controls. Of the immunized animals challenged in the cornea with strain MP, 5 X 10(4) PFU, only 18% developed a mild keratitis, while 96% of unimmunized controls developed severe keratitis. Mice immunized subcutaneously with MP and subsequently challenged corneally with other HSV-1 strains (mP, F, or KOS) were also protected from development of severe keratopathy.