Various Inbred Strains Of Mice Research Articles

Haematological Profile of Various Inbred Strains of Mice Maintained at IMTech Centre for Animal Resources and Experimentation (iCARE)

Animal models are frequently employed in scientific studies to collect data from an entire set of experiments. Haematological tests on these laboratory mice are essential for confirming scientific findings because diverse mouse strains have been used to examine various diseases and novel therapeutic methods. This work is aimed to establish haematological values in mouse strains used in biomedical research. Blood samples were taken from the retro-orbital sinus of mice from various strains and haematological parameters including total White Blood Cells (WBC), Red Blood Cells (RBC), Haemoglobin (HGB), Haematocrit (HCT), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH), Mean Corpuscular Haemoglobin Concentration (MCHC), Red Blood Cell Dimension Width ( RDW), platelets, Mean Platelet Volume (MPV) and Platelet Dimension Width (PDW) were assessed. Compared to other strains (BALB/c, M:9.61, F:9.51; C57BL6/N, M:10.13, F:10.73; DBA/2, M:11.96, F:10.88), the mean values of WBCs (*103/μL) in DBA/1 mice were higher (M:14.02; F:14.65) and lower in NOD (M:7.14; F:6.54). The mean RBCs in different strains of mice used in this study ranged from 8.78-11.67*106/μL. Male mean haemoglobin valves in BALB/c, C57BL/6N, DBA/1, DBA/2 and NOD were 14.60, 13.32, 13.00, 14.35 and 13.48 (g/dL), respectively, while in females were 14.3, 14.09, 13.11, 12.65 and 13.24 (g/dL), respectively. The mean platelet counts in NOD mice (M:1826.60 and F:1557.80*103/μL) were significantly higher than other strains. Haematological profiles of the mice used in the study were consistent as reported previously for mice maintained in different animal facilities. The haematological values presented in this study can be used as reference values in biomedical research.

Zygote Microinjection for Creating Gene Cassette Knock-in and Flox Alleles in Mice.

CRISPR-Cas technology has enabled the rapid and effortless generation of genetically modified mice. Specifically, mice and point mutant mice are readily produced by electroporation of CRISPR factors (and single-stranded oligo DNA donors) into the zygote. In contrast, gene cassette (>1 kb) knock-in and floxed mice are mainly generated by microinjection of CRISPR factors and double-stranded DNA donors into zygotes. Genome editing technologies have also increased the flexibility of genetically modified mice production. It is now possible to introduce the intended mutations in the target genomic regions in a number of beneficial inbred mouse strains. Our team has produced over 200 gene cassette knock-in mouse lines, and over 110 floxed mouse lines by zygote microinjection of CRISPR-Cas9 following requests from several countries, including Japan. Some of these genome editing used BALB/c, C3H/HeJ, and C57BL/6N inbred strains, however most used C57BL/6J. Unlike the electroporation method, genome editing by zygote microinjection in various inbred strains of mice is not that easy. However, gene cassette knock-in and floxed mice on single inbred genetic backgrounds are as critical as genetic humanized, fluorescent reporter, and conditional knockout mouse models. Therefore, this article presents the protocol for the zygote microinjection of CRISPR factors and double-stranded DNA donors in C57BL/6J mice for generating gene cassette knock-in and floxed mice. This article exclusively focuses on nuclear injection rather than cytoplasmic injection. In addition to zygote microinjection, we outline the timeline for the production process and peripheral techniques such as induction of superovulation and embryo transfer.

Zygote Microinjection for Creating Gene Cassette Knock-in and Flox Alleles in Mice

CRISPR-Cas technology has enabled the rapid and effortless generation of genetically modified mice. Specifically, mice and point mutant mice are readily produced by electroporation of CRISPR factors (and single-stranded oligo DNA donors) into the zygote. In contrast, gene cassette (>1 kb) knock-in and floxed mice are mainly generated by microinjection of CRISPR factors and double-stranded DNA donors into zygotes. Genome editing technologies have also increased the flexibility of genetically modified mice production. It is now possible to introduce the intended mutations in the target genomic regions in a number of beneficial inbred mouse strains. Our team has produced over 200 gene cassette knock-in mouse lines, and over 110 floxed mouse lines by zygote microinjection of CRISPR-Cas9 following requests from several countries, including Japan. Some of these genome editing used BALB/c, C3H/HeJ, and C57BL/6N inbred strains, however most used C57BL/6J. Unlike the electroporation method, genome editing by zygote microinjection in various inbred strains of mice is not that easy. However, gene cassette knock-in and floxed mice on single inbred genetic backgrounds are as critical as genetic humanized, fluorescent reporter, and conditional knockout mouse models. Therefore, this article presents the protocol for the zygote microinjection of CRISPR factors and double-stranded DNA donors in C57BL/6J mice for generating gene cassette knock-in and floxed mice. This article exclusively focuses on nuclear injection rather than cytoplasmic injection. In addition to zygote microinjection, we outline the timeline for the production process and peripheral techniques such as induction of superovulation and embryo transfer.

Assessment of Genetic Purity of Inbred Strains of Mice using Microsatellite Markers

Monitoring of genetic make-up of inbred strains of mice is one of the most essential and basic requirements to assure the continued purity and homogeneity of the strains. It further helps in maintaining phenotypic characteristics of mice strain, which in turn, ensures the reproducibility of research outcomes between the group of mice and over time. In the present study, the phenotypic and genotypic characteristics of various inbred strains of mice maintained in our Animal Facility were assessed to ascertain their purity. The mice exhibited strain-specific phenotypic characters and skin coat colours in accordance with the published profile of the specific strains. The average litter size of C57BL/6 and BALB/c mice, the most commonly used strains of mice, was calculated over different generations and found to be 5 to 6.6 and 4 to 6, respectively. For checking the genetic purity of mice, more than 1700 tissue samples (ear punched tissue) were collected from various strains of mice. Genomic DNA was isolated from the tissue samples and subjected to PCR-based microsatellite analysis. Amplified PCR products of genomic DNA of tested mice showed identical amplicon base-pair length as per the published profile in the MGI database, indicating the purity and uniformity of the mice.

Intimal hyperplasia in murine models.

The most commonly used procedures to induce arterial injury in mice are carotid artery ligation with cessation of blood flow and mechanically-induced denudation of endothelium in the carotid or the femoral arteries. Both procedures result in neointimal hyperplasia after two to three weeks. A survey of various inbred strains of mice shows that strain-specific differences in susceptibility to injury-induced neointimal hyperplasia are different than those for susceptibility to diet-induced atherosclerosis, with strains identified as susceptible to both neointimal hyperplasia and atherosclerosis, resistant to both, susceptible to atherosclerosis but resistant to neointimal hyperplasia, or resistant to atherosclerosis but susceptible to neointimal hyperplasia. Inflammatory cells such as T and B lymphocytes, which are contributory to atherosclerosis, are protective against injury-induced neointimal hyperplasia. In contrast, the infiltration of monocytes into the site of injury and their differentiation to macrophages favor neointimal hyperplasia similar to their pathogenic role in atherosclerosis. The regulatory role of lymphocytes and macrophages in neointimal hyperplasia is related to the production of cytokines such as interferon-gamma and tumor necrosis factor-alpha, respectively. Interestingly, inducible nitric oxide synthase (iNOS) activity appears to inhibit neointimal hyperplasia in the endothelial denudation model but contributes to neointimal hyperplasia when arterial injury is induced by periadventitial cuff placement. The difference appears to be due to the time required for endothelial recovery and the participation of inflammatory cells. Thus, although arterial injury-induced neointimal hyperplasia results in similar vascular occlusion as progressive atherosclerosis, the pathology and mechanism of the two disease processes are quite different.

Lethal and severe coronary arteritis in DBA/2 mice induced by fungal pathogen, CAWS, Candida albicans water-soluble fraction

CAWS is a microbial pathogen-associated molecular patterns (PAMPs) produced by Candida albicans. CAWS is a mannoprotein–beta-glucan complex and secreted into the culture supernatant. CAWS has various biological effects, causing acute shock and disrupting vascular permeability. Intraperitoneal administration of CAWS induces coronary arteritis in various strains of inbred mice. The CAWS-induced coronary arteritis is strain-dependent and most severe in DBA/2 mice with a significant number of these animals expiring with cardiomegaly during the observation period. In vivo and in vitro, splenocytes of DBA/2 mice produced various cytokines, such as IL-6, TNF-α, and IFN-γ in response to CAWS. GM-CSF was also produced in response to CAWS. The production of cytokines was significantly enhanced in the presence of recombinant GM-CSF. In contrast, anti-GM-CSF significantly reduced the production of TNF-α and IFN-γ. Augmented production of cytokines in response to CAWS would be a key to the severity of coronary arteritis.

Sleep During Concanavalin-A-Induced Hepatitis and Peritonitis in Inbred Mice

To assess the suitability of concanavalin-A-induced hepatitis as a model for investigating the relationships between hepatic disease and alterations in somnolence. We characterized the sleep patterns of various strains of inbred mice undergoing ConA-induced inflammation. Southern Illinois University School of Medicine, Springfield, IL. Intravenous or intraperitoneal administration of concanavalin-A. Inbred mice. Intravenous and intraperitoneal administration of concanavalin-A both elicited strain-dependent changes in slow-wave sleep. ConA treatment also reduced spontaneous locomotor activity. ConA-induced changes in slow-wave sleep varied with dose, route of administration, and circadian period of administration. As compared with the other strains, C57BL/6J mice had lower serum concentrations of interferon-gamma at 8 hours after ConA administration. These data provide the first demonstration that sleep enhancement and reduced locomotor activity accompany hepatic inflammation in mice.

Brugia malayi: establishment in inbred and outbred strains of mice

Immunocompetent mouse model for human filarial parasite Brugia malayi is urgently required in view of the paucity of commercial reagents for other susceptible rodent viz. mastomys and gerbil. Genes within the major histocompatibility complex have been reported to influence the susceptibility of mouse to helminth parasites. Attempts have therefore been made in the present investigation to experimentally infect various inbred strains of mice viz. NZB/BINJ, BALB/c, AKR, C 3H, and SJL/J with H-2 haplotype (H-2: d, d, k, k, s, respectively) and outbred strains of mice viz. Parks and Swiss. Findings indicate that susceptibility of mice to B. malayi is strain associated. This is the first report on the successful completion of full developmental cycle of subperiodic B. malayi in NZB/BINJ, an immunocompetent mouse strain. In some of the other strains, partial development or low degree of establishment of worms was observed. Index descriptors and abbreviations: Brugia malayi; nematoda; lymphatic filaria; susceptibility; inbred mice; outbred mice; immunocompetent; L4; preadult.

Mouse genetic models for prepulse inhibition: an early review.

Prepulse inhibition (PPI) is the phenomenon in which a weak prepulse stimulus attenuates the response to a subsequent startling stimulus. Patients with schizophrenia and some other neuropsychiatric disorders have impaired PPI. Impaired PPI in these patient populations is thought to reflect dysfunctional sensorimotor gating mechanisms. Recently, various inbred mouse strains and genetically modified mouse lines have been examined to investigate the potential genetic basis of sensorimotor gating. This review provides a synopsis of the use of mouse models to explore genetic and neurochemical influences on PPI. Studies describing the PPI responses of various inbred strains of mice, mice with genetic mutations, and mice treated with various drugs prior to July 2001 are reviewed. The continuous nature of the distribution of PPI responses among inbred strains of mice indicates that PPI is a polygenic trait. Findings from spontaneous and gene-targeted mutants suggest that mutant mice are important tools for dissecting and studying the role of single genes and their products, and chromosomal regions in regulating PPI. Pharmacological studies of PPI have typically confirmed effects in mice that are similar to those reported previously in rats, with some important exceptions. The use of mice to study PPI is increasing at a dramatic rate and is helping to increase our understanding of the biological basis for sensorimotor gating.

Genetic influences on secondary degeneration and wound healing following spinal cord injury in various strains of mice.

Various inbred strains of mice exhibit dramatic differences in sensitivity to excitotoxic cell death induced by systemic injections of kainic acid (KA). The present study evaluates whether the same strains are also differentially sensitive to secondary degeneration after spinal cord injury, in which excitotoxic cell death is thought to play a pathogenic role. Spinal cord crush injuries were produced at T9 in two inbred strains that are resistant to KA-induced excitotoxic cell death (C57Bl/6 and Balb/c) and four strains that are sensitive (CD-1, FVB/N, 129T2 Sv/EMS, and C57Bl/10). The spinal cord was prepared for light microscopy at intervals from 1 to 56 days postinjury, and the area of damaged tissue (termed lesion size) and amount of cavitation were determined by quantitative image analysis. Lesion size increased between 1 and 7 days in all strains and then decreased steadily in a wound-healing process that occurs uniquely in mice. The extent of cavitation also gradually decreased from 7 to 56 days in all strains. Although lesion area and cavitation decreased in all strains, there were significant differences in lesion size and cavitation across strains. Specifically, lesion areas in the KA-sensitive strains FVB/N, 129T2 Sv/EMS, and CD-1 were significantly larger at 56 days postinjury than in the KA-resistant strains C57Bl/6 and Balb/c. We conclude that the genetic differences that confer resistance and sensitivity to KA-induced neurotoxicity also modify the secondary degenerative processes that occur after spinal cord injury, so that resistance to excitotoxic injury leads to smaller overall lesions and a more effective wound-healing response.

Effect of calorie restriction on mortality kinetics in inbred strains of mice following 7,12-dimethylbenz[a]anthracene treatment.

Calorie restriction (CR) has long been known to increase longevity and to delay the onset and to decrease the incidence of many age-related disease processes. The mechanism(s) by which these outcomes are attained is unidentified. This experiment was designed to examine whether differences existed in the extent to which various inbred strains of mice respond to CR. This work explored whether carcinogen-treated animals could be used to facilitate this aim by decreasing the time needed to observe differences in mortality kinetics between CR mice and ad libitum (AL) fed controls. Female mice from each of eight strains (A/J, BALB/c, C3H, C57BL/6, DBA/2J, FVB/J, NMRI, and 129/J) were given a single oral dose (65 mg/kg) of the carcinogen 7,12-dimethylbenz[a]anthracene and subsequently fed AL or calorically restricted. Following carcinogen treatment, the spectrum of lesions observed demonstrated genotypic variability, thereby complicating comparison among the inbred strains examined. However, in terms of the magnitude of alteration in mortality kinetics observed, a statistical analysis revealed that differences exist among the various strains of mice in their response.

Association of a determinant on mouse chromosome 18 with experimental severe Plasmodium berghei malaria.

Experimental severe malaria (ESM; also known as experimental cerebral malaria) is an acute lethal syndrome caused by infection with Plasmodium berghei ANKA and associated with coma and other neurological manifestations in mice. Various inbred strains of mice exhibit differences in susceptibility to the development of ESM. For example, C57BL/6 mice are highly susceptible and DBA/2 mice are relatively resistant. We report here the results of a genomewide scan for host genomic regions that control resistance to ESM in DBA/2 mice using an F(2) intercross population of susceptible and resistant strains. A region of mid-chromosome 18 was found to be a major determinant of resistance to ESM.

Differential Susceptibility of Inbred Mouse Strains to Helicobacter pylori Infection

Background: Host factors play an important part in the pathogenesis of Helicobacter pylori -associated disease. The aim of this study was to screen various inbred strains of mice for genetic differences in susceptibility to H. pylori infection. Methods: Mice of strains BALB/cJ, C.B-17- Prkdc scid , C3H/HeJ, C3H/HeN, C57BL/6J, C57BL/6J- Il10 tm1Cgn , DBA/2J, and FVB/N were inoculated intragastrically with H. pylori SS1. At 1, 4 and 6 months after inoculation, mice were necropsied, and bacterial cultures and histologic studies of the stomachs were performed. Results : Significant differences in the level of colonization by H. pylori were observed among inbred strains at each time of infection. These differences were most distinct at 4 months after inoculation with highest levels in strains C3H/HeJ and C3H/HeN and lowest in strains FVB/N, C57BL/6J and C57BL/6J- Il10 tm1Cgn. Infected mice revealed a mild increase in inflammatory cells compared with controls at 1 and 4 months, but not at 6 months after inoculation. The host strain effect on gastric disease was fairly mild, with two exceptions. Firstly, infected Il10 tm1Cgn mice developed a severe, hyperplastic gastritis, indicating that interleukin-10 is an important regulator of the inflammatory response to H. pylori. Secondly, infected C3H/HeN mice had a propensity to develop lymphoid aggregates in the gastric mucosa. Conclusions: The strain differences described here will be useful for the design of genetic mapping studies in mice to elucidate the genes controlling gastric infection by H. pylori. Our results further show that genetically altered mice are a valuable tool for identifying candidate genes possibly contributing to susceptibility to H. pylori infection.

Identifying genetic influences on sleep: an approach to discovering the mechanisms of sleep regulation.

Comparisons of sleep patterns of various inbred strains of mice have revealed differences in daily amounts of slow-wave sleep and rapid-eye movement sleep, in circadian patterns of sleep, and in some parameters of the electroencephalograms both in healthy mice and in mice undergoing microbial infections. Technical considerations will probably be an important variable in achieving consensus between different independent studies that use a genetic approach to identify sleep-regulatory genes or mechanisms. However, despite such differences, current data suggest that both normal sleep and various sleep disorders either have a genetic basis or are influenced by genetically determined physiologic or environmental predispositions. Excessive sleepiness, abnormal sleep patterns, nonrestorative sleep, and fatigue are becoming increasingly pervasive in modern society. Identifying genes that influence vigilance may ultimately contribute to a better understanding of the processes that control normal sleep and contribute to sleep disorders and may eventually promote the development of interventions to prevent or alleviate these disabling medical conditions.

Strain-Dependent Vascular Remodeling Phenotypes in Inbred Mice

We have recently established a mouse model of arterial remodeling in which flow in the left common carotid artery of FVB mice was interrupted by ligation of the vessel near the carotid bifurcation, resulting in a dramatic reduction of the lumen as a consequence of a reduction in vessel diameter and intimal lesion formation. In the present study we applied this model to various inbred strains of mice. Wide variations in the remodeling response with regard to reduction in vessel diameter, intimal lesion formation, lumen area, and medial hypertrophy were found. On carotid artery ligation SJL/J mice revealed the most extensive inward remodeling leading to an approximate 78% decrease in lumen area while lumen narrowing in FVB/NJ mice was largely due to extensive neointima formation as a result of smooth muscle cell (SMC) proliferation. Significant positive remodeling in the contralateral right carotid artery with a >20% increase in lumen area was observed in SM/J and A/J mice. An in vitro comparison of growth properties of SMC isolated from FVB/NJ mice and a strain that exhibited very little SMC proliferation (C3H/HeJ) demonstrated accelerated growth of SMC from FVB/NJ following serum stimulation. In vivo, SMC proliferation in the FVB/NJ strain was preceded by a 37% loss of medial SMC occurring within the 2 days after ligation, however, cell death was not detectable in C3H/HeJ mice. These findings suggest that the mechanisms leading to lumen narrowing in the vascular remodeling process are genetically controlled.

A quantitative genetic analysis of slow-wave sleep and rapid-eye movement sleep in CXB recombinant inbred mice.

Various inbred strains of mice show different daily amounts of slow-wave sleep (SWS) and rapid-eye movement sleep (REMS), suggesting the possibility of genetic influences on sleep propensity. Previous work by others studying the spontaneous sleep patterns of seven strains of CXB recombinant inbred (RI) mice suggested several candidate quantitative trait loci (QTLs) associated with variation in REMS. Extending this approach, we evaluated the sleep patterns of 13 CXB RI strains and conducted linkage analyses based on 223 discrete informative loci. The probability density distribution of light phase REMS for the CXB RI strains showed deflections that correspond approximately to the parental phenotypes. This type of pattern is consistent with the presence of a low number of major effect quantitative trait loci. Regions of chromosomes 4, 16, and 17 showed provisional linkage to strain variation in REMS. The distribution of loci further suggested that dark phase and light phase REMS may be regulated by different genetic factors. Probabilities of linkage were not sufficient for declaration of a quantitative trait locus for REMS but were sufficient to warrant further analysis either with additional RI strains or with F2 panels.

Differential reactivity of brain microvascular endothelial cells to TNF reflects the genetic susceptibility to cerebral malaria.

Upon infection with Plasmodium berghei ANKA (PbA), various inbred strains of mice exhibit different susceptibility to the development of cerebral malaria (CM). Tumor necrosis factor-alpha (TNF) and interferon-gamma (IFN-gamma) have been shown to be crucial mediators in the pathogenesis of this neurovascular complication. Brain microvascular endothelial cells (MVEC) represent an important target of both cytokines. In the present study, we show that brain MVEC purified from CM-susceptible (CM-S) CBA/J mice and CM-resistant (CM-R) BALB/c mice exhibit a different sensitivity to TNF. CBA/J brain MVEC displayed a higher capacity to produce IL-6 and to up-regulate intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in response to TNF than BALB/c brain MVEC. In contrast, no difference was found in the induction of E-selectin after TNF challenge. CM-S brain MVEC were also significantly more sensitive to TNF-induced lysis. This differential reactivity to TNF was further substantiated by comparing TNF receptor expression on CM-S and CM-R brain MVEC. Although the constitutive expression of TNF receptors was comparable on cells from the two origins, TNF induced an up-regulation of both p55 and p75 TNF receptors in CM-S, but not in CM-R brain MVEC. A similar regulation was found at the level of TNF receptor mRNA, but not for receptor shedding. Although a protein kinase C inhibitor blocked the response to TNF in both the brain MVEC, an inhibitor of protein kinase A selectively abolished the response to TNF in CM-R, but not CM-S brain MVEC, suggesting a differential protein kinase involvement in TNF-induced activation of CM-S and CM-R brain MVEC. These results indicate that brain MVEC purified from CM-S and CM-R mice exhibit distinctive sensitivity to TNF This difference may be partly due to a differential regulation of TNF receptors and via distinct protein kinase pathways.

Differential susceptibility of inbred mouse strains to dextran sulfate sodium-induced colitis.

Dextran sulfate sodium (DSS)-induced murine colitis represents an experimental model for human inflammatory bowel disease. The aim of this study was to screen various inbred strains of mice for genetically determined differences in susceptibility to DSS-induced colitis. Mice of strains C3H/HeJ, C3H/HeJBir, C57BL/6J, DBA/2J, NOD/LtJ, NOD/LtSz-Prkdc(scid)/Prkdc(scid), 129/SvPas, NON/LtJ, and NON.NOD-H2g7 were fed 3.5% DSS in drinking water for 5 days and necropsied 16 days later. Ceca and colons were scored for histological lesions based on severity, ulceration, hyperplasia, and area involved. Image analysis was used to quantitate the proportion of cecum ulcerated. Histological examination revealed significant differences among inbred strains for all parameters scored. In both cecum and colon, C3H/HeJ and a recently selected substrain, C3H/HeJBir, were highly DSS susceptible. NOD/LtJ, an autoimmune-prone strain, and NOD/LtSz-Prkdc(scid)/Prkdc(scid), a stock with multiple defects in innate and adoptive immunity, were also highly DSS susceptible. NON/LtJ, a strain closely related to NOD, was quite DSS resistant. The major histocompatibility (MHC) haplotype of NOD mice (H2g7), a major component of the NOD autoimmune susceptibility, was not crucial in determining DSS susceptibility, since NON mice congenic for this MHC haplotype retained resistance. C57BL/6J, 129/SvPas, and DBA/2J mice showed various degrees of susceptibility, depending upon the anatomical site. A greater male susceptibility to DSS-induced colonic but not cecal lesions was observed. In summary, this study demonstrates major differences in genetic susceptibility to DSS-induced colitis among inbred strains of mice. Knowledge of these strain differences in genetic responsiveness to acute inflammatory stress in the large intestine will permit design of genetic crosses to elucidate the genes involved.

A Model of Peptide-Induced Lupus Autoimmune B Cell Epitope Spreading Is Strain Specific and Is Not H-2 Restricted in Mice

Abstract Anti-Sm is a common and specific autoantibody found in systemic lupus erythematosus. The peptide PPPGMRPP from Sm B/B′ is an early target of the autoimmune response in some anti-Sm-positive human patients. After immunization with this peptide on a MAP backbone, rabbits develop anti-Sm autoantibodies with B cell epitope spreading of the autoimmune response as well as other features of lupus autoimmunity. Various strains of inbred mice have been immunized with peptide PPPGMRPP or PSQQVMTP (nonantigenic region of Sm B/B′) in Freund’s adjuvant or with no peptide. All peptide-immunized mouse strains eventually develop high titers of specific anti-peptide of immunization Abs. Mice immunized with Freund’s adjuvant alone have no measurable Ab binding to the PPPGMRPP peptide. With time, nearly half the mouse strains tested develop Abs that react with additional regions of Sm B/B′ and Sm D. All the regions bound by mouse serum are major epitopes of the human systemic lupus erythematosus anti-Sm response. These same strains also develop significant anti-Sm and anti-nuclear ribonucleoprotein titers. In addition, some of these strains demonstrate positive anti-nuclear Abs and anti-dsDNA Abs. Experiments with congenic H-2 mice demonstrate that the H-2 region does not play a role in spreading the immune response from the peptide of immunization to other epitopes of the spliceosome. These results present a new murine model of B cell epitope spreading and lupus autoimmunity induced by peptide immunization that is strain specific and not apparently dependent upon the loci at H-2.

Genetic control of immune response to a synthetic fimbrial antigen of Actinobacillus actinomycetemcomitans.

The incidence of infection by Actinobacillus actinomycetemcomitans, one of the important pathogens in human periodontal diseases, has been reported to be associated with racial background and genetic factors. We attempted to determine the genetic regulation of immune responses to A. actinomycetemcomitans fimbriae, an attachment factor, using various inbred strains of mice. For this purpose, we synthesized an oligopeptide antigen using the amino acid sequence of the fimbriae and conjugated this antigen to branched lysine polymer resin beads. After immunization with the synthetic A. actinomycetemcomitans fimbrial antigen, serum antibody levels and the delayed-type hypersensitivity (DTH) reaction to the antigen were measured by enzyme-linked immunosorbent assay (ELISA) and footpad swelling responses, respectively. The strains of mice found to be high-IgG responders to the antigen were B10.HTT, B10.RIII, B10.A (5R) and B10.S (9R). These results indicate that mice with E(beta s):E(alpha k), E(beta r):E(alpha r) and E(beta b):E(alpha k) respond strongly to the synthetic peptide. All of the high-IgG responders showed a high DTH response. A cell transfer experiment confirmed that CD4 T cells mediated with DTH response to the synthetic peptide. Thus, the results of this study demonstrate that the immune responses to A. actinomycetemcomitans fimbriae are genetically controlled.