Age-related changes in contact photosensitivity differ among mouse strains

There are differences among mouse strains in the age-related changes in reactivity to the contact photosensitizer tetrachlorosalicylanilide (TCSA). We found a tendency to lower reactions in older mice, with some strains showing declines from an early age (BALB/cJ, MRL/MpJ +/+, MRL/MpJ lpr/lpr and SJL/J). Others had increasing reactions until about 30-50 weeks of age before declining (DBA/1J, C3H/HeJ, and A/J) and one strain (C57BL/6J) had increased reactivity with age. There are also differences in the role of cyclophosphamide-sensitive T-suppressor cells in these age-related changes. In some mouse strains, BALB/cJ, C57BL/6J, A/J, DBA/1J and C3H/HeJ, age-related changes in reactivity to TCSA are independent of changes in cyclophosphamide-sensitive suppressor cells. In other strains, MRL/MpJ +/+, MRL/MpJ lpr/lpr and SJL/J, the development of cyclophosphamide-sensitive suppressor cells is responsible for the initial, though not later, stages of the age-related decline in reactivity.     

Virus-induced diabetes mellitus. X. Attachment of encephalomyocarditis virus and permissiveness of cultured pancreatic beta cells to infection.

Monolayers of pancreatic β-cells from strains of mice susceptible (SJL/J) and resistant (C57BL/6J) to the development of virus-induced diabetes mellitus were inoculated with the M variant of encephalomyocarditis (EMC) virus. Immunofluorescence showed that viral antigens appeared in up to 10 times more β cells from susceptible SJL/J mice than from resistant C57BL/6J mice. Infectious center assays revealed that 10–30 times more SJL/J β cells contained infectious virus than C57BL/6J β cells. Viral attachment experiments showed no difference in the binding of EMC virus when embryonic fibroblasts, pancreatic fibroblasts, and kidney cells from SJL/J and C57BL/6J mice were compared. However, at least twice as much virus attached to the pancreatic β cells from susceptible than from resistant strains of mice. Our data suggest that genetically determined differences in viral receptors on the surface of β cells may be one of the factors controlling susceptibility to EMC-induced diabetes mellitus.     

Up-regulation of MHC class I expression accompanies but is not required for spontaneous myopathy in dysferlin-deficient SJL/J mice

We found that up-regulation of major histocompatibility complex (MHC) class I expression accompanies, but is not required for, appearance of spontaneous myopathy in SJL/J mice. In some neuromuscular diseases, MHC class I expression is markedly up-regulated in muscles, though the consequences of this up-regulation for pathology are not clear. To study MHC class I in myopathy, we compared muscles of SJL/J mice to muscles of SJL/J mice that were also MHC class I-deficient due to targeted mutation in the beta-2-microglobulin gene (SJL/J B2m (-/-) mice). SJL/J mice show spontaneous myopathy and have a mutation in the dysferlin gene, a gene which is also mutated in human limb-girdle muscular dystrophy type 2B (LGMD2B). Muscles of eight-month-old SJL/J mice had higher levels of MHC class I expression than muscles of either C57BL/6J (wild-type) or SJL/J B2m (-/-) mice. In contrast, the percentage of abnormal muscle fibers was similar in SJL/J and SJL/J B2m (-/-) muscles. Invading Mac-1(+) cells were most abundant in SJL/J B2m (-/-) muscles, moderately abundant in SJL/J muscles, and rare in C57BL/6J muscles. Thus, MHC class I was markedly up-regulated in SJL/J muscles, but this high level of MHC class I was not necessary for the appearance of myopathy.     

Age-related polymorphism of thymus subpopulations in inbred mice.

There are striking age-related changes in the demography of thymus lymphocytes, i.e. in thymus-cell subpopulations of BALB/c and SJL mice; these changes occur in the proportion of cells, identified by various markers, and by the membrane density of these markers. The thymuses of both strains undergo an age-related increase in the proportion of CD4+ CD8- cells and decrease in CD4+ CD8+ cells. Age-related changes in cells that are Pgp-1+ also show marked strain differences: Pgp-1+ cells increase in SJL, but not in BALB/c thymuses. In both strains, cells with high density of Pgp-1 appear in later life, though this is more marked in the thymus of SJL, which also shows a higher relative density at an advanced age, than do BALB/c mice. Furthermore, the per cent of cells with high density of Pgp-1 is larger in thymuses of SJL than in BALB/c mice. The percentage of CD45+ thymocytes remains unchanged, as animals age. Thymocyte-membrane densities of CD-45 undergo age-related increases in both SJL and BALB/c. The per cent of cells with high density of CD-45 is similar in both strains. Individual variations in relative size of subpopulations in SJL mice of the same age are greater in old than in young mice; this increase in heterogeneity is manifested by increase in standard deviation. Corresponding significant changes have not been observed in BALB/c or C57BL/6 mice. Thus, we have detected an intrastrain variation which may reflect age-related effects of the impact of stochastic events.     

Quantitative, not qualitative, differences in CD8(+) T cell responses to Theiler's murine encephalomyelitis virus between resistant C57BL/6 and susceptible SJL/J mice

Theiler's murine encephalomyelitis virus (TMEV) infection of the CNS induces an immune-mediated demyelinating disease in susceptible mouse strains and serves as a relevant infection model for human multiple sclerosis. However, it is not yet clear what immunological parameters determine the susceptibility of SJL/J mice compared to resistant mice. We have here compared the TMEV-specific CD8(+) T cell responses in highly susceptible SJL/J mice with those of highly resistant C57BL/6 mice. Our results clearly indicate that the levels of initial responses of infiltrating CD8(+) T cells to viral capsid proteins are higher in resistant C57BL/6 mice compared to susceptible SJL/J mice. However, the level of virus-specific CD8(+) T cells was much more rapidly reduced in resistant C57BL/6, resulting in a higher CD8(+) T cell level in SJL/J mice later in viral infection. The activation states, cytokine production, as well as the cytolytic function of the CD8(+) T cells were similar to each other in these mice. These results suggest that an initial induction of a vigorous CD8(+) T cell response to TMEV is critically important for the resistance to virally induced demyelinating disease.     

Age-Dependent Changes in Isotype Expression and Down-Regulation of C57BL/6 Mice

Age-related changes in antibody response and tolerance inducibility are polymorphic; in this paper isotype changes in ageing C57BL/6 mice are examined. Female C57BL/6 mice of various ages were immunized with either heat-aggregated RGG (a-RGG) or phosphorylcholine conjugate of RGG (PC-RGG); other animals of the same ages were given aggregate free RGG, followed by injections with either aggregated RGG or haptenated RGG. Sera from these four groups were analysed for antibody isotype. The data presented here indicate that age-related changes in isotype predominance and magnitude are different for different determinants. The capacity to be down-regulated appeared to undergo different age-related changes with different isotypes: there is split tolerance in isotypes. Age-dependent changes in T- and B-cell tolerance could be deduced by comparing responses of animals to hapten and to carrier determinants. In 5-week-old animals tolerance to hapten was more profound than tolerance to carrier. It was concluded that T-cell regulation dominated the response at this age. With advancing age, i.e. by 95 weeks, tolerance is observed in response to hapten but not in response to carrier determinants. We concluded that suppressor cells were induced by aggregate free RGG and affected the response of 'naive' but not of 'experienced' B cells.     

Lymphokine-activated killer (LAK) cells: I. Age-dependent decline of LAK cell-mediated cytotoxicity

Experiments were designed to assess age-related changes in generation of lymphokine-activated killer (LAK) cells and to test whether these changes can be modified by diets differing in the proportion of polyunsaturated to saturated fatty acids (P/S). Ficoll-Hypaque-isolated spleen lymphocytes of rodent chow-fed, 6-85-week-old C57BL/6 (H-2b), 8-81-week-old C57BL/10 (H-2b) and 6-62-week-old SJL (H-2s) mice were cultured in IL-2-containing medium and examined in 51Cr cytotoxicity assay. Similarly, Ficoll-Hypaque-isolated spleen lymphocytes of 6-36-week-old SJL mice fed diets which differed in the ratio of polyunsaturated/saturated fatty acids were cultured in IL-2-containing medium and assayed for cytotoxicity. Age-related decline of LAK cell-mediated cytolysis was observed in mice of both H-2b and H-2s haplotype. The age-related decline of LAK cell-mediated cytolysis was the consequence of age-related decrease in the rate of LAK cell precursor maturation. SJL mice fed from birth with diets differing in P/S did not differ in LAK cell-mediated cytolysis.     

The induction of immune complex deposits in mice by peroral and parenteral administration of mercuric chloride: strain dependent susceptibility.

Female Balb/c and SJL mice exposed to HgCl2 by subcutaneous injection or via drinking water for up to 6 months showed immunostimulation with increased concentrations of immunoglobulins (Ig) in the serum. The Ig isotype pattern was dependent both on the strain and the use of immunopotentiation by addition of Freund's complete adjuvant (FCA). Balb/c mice showed a T cell dependent pattern, whereas the SJL mice developed an increase also in T cell independent isotypes. This latter pattern shifted to show T cell dependency after an initial addition of FCA. FCA also converted the lack of stimulation in C57BL/6J mice to a low response with a T cell dependent isotype pattern. No correlation emerged between the body burden of mercury, as assessed by the concentration in the kidneys, and the degree of immunostimulation by mercury. Mice showing a stimulation of the immune system developed mesangial immune complex (IC) glomerulonephritis and, later on, IC deposits in renal, splenic, and hepatic vessel walls with an isotype pattern corresponding to that seen in the serum.     

Specific anosmia in the laboratory mouse

As an approach to a general theory of olfaction, different specific anosmia phenotypes characterized by different profiles of odorant sensitivities have been proposed for humans. In the present experiments, male inbred mice were tested for relative odorant sensitivity using a conditioned aversion technique and odors classified as primary or complex for humans. C57BL/6J and C57BL/10J mice appeared to be less sensitive to the primary odorant isovaleric acid than were males of seven other inbred strains (A/J, AKR/J, BALB/cJ, C3HeB/FeJ, DBA/2J, SJL/J, and SWR/J). In comparisons of C57BL/6J and AKR/J strains, the relative insensitivity of C57 to isovaleric acid did not generalize to the musklike primary odor of pentadecalactone or to the complex odor of amyl acetate. The C57BL/6J genotype may provide an animal model of a specific anosmia as characterized among humans.Supported in part by U.S. Public Health Service Grants MH-11218, NS-08814, and MH-05116 and by an award from the Florida State University Committee on Faculty Research Support. Portions of the data were presented at the meeting of the Behavioral Genetics Association, Austin, Texas, March 1975.     

IgG subclass responses to Theiler's murine encephalomyelitis virus infection and immunization suggest a dominant role for Th1 cells in susceptible mouse strains.

Inbred mouse strains differ in susceptibility to Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease. A strong correlation between disease susceptibility and delayed-type hypersensitivity (DTH) has been previously demonstrated, but no strong correlation between disease susceptibility and total anti-TMEV ELISA titres was shown. Since both DTH and IgG2a antibody production are regulated by CD4+ Th1 cells, we investigated three strains of mice to determine whether antivirus IgG2a antibody levels, like DTH in previous studies, correlated with disease susceptibility. Susceptible SJL/J, intermediately susceptible C3H/HeJ, and resistant C57BL/6 mice were infected intracerebrally (i.c.) with the BeAn strain of TMEV and monitored for clinical signs of demyelination and for levels of TMEV-specific antibody of different IgG subclasses using a particle concentration fluorescence immunoassay (PCFIA). Resistant C57BL/6 mice were found to have significantly lower concentrations of total anti-TMEV antibody than susceptible SJL/J mice and intermediately susceptible C3H/HeJ mice show variable antibody responses. A predominance of anti-TMEV IgG2a (Th1 regulated) antibody was seen in susceptible and intermediately susceptible mice, whereas resistant mice displayed a predominant anti-TMEV IgG1 (Th2 regulated) response accompanied by a marked deficiency of IgG2a. In contrast, immunization of C57BL/6 mice with UV-inactivated TMEV in adjuvant revealed that this strain was not defective either in its ability to generate high levels of anti-TMEV antibody or in its ability to produce IgG2a antibody. These results suggest that the antivirus IgG subclass profile is dependent upon the immunization route, virus viability and/or the use of adjuvant and that the levels of antivirus subclasses may be predictive of disease susceptibility.     

Differential effects of age on motor performance in two mouse strains

The performance of male A/J and C57BL/6J mice from three age groups (4, 18, and 24 months) was observed in a battery of tests designed to assess age-related impairments in motor abilities. A/J mice were superior to C57BL/6J mice in tasks requiring upper body strength, such as tests of grip strength and tightrope performance. C57BL/6J mice were superior performers in tasks requiring balance and coordination, such as movement on stationary and rotating rods. In addition, the C57BL/6J strain generally exhibited greater locomotor activity, such as measured in open field and wheel-running tests. Significant age-related deficits were observed among A/J mice in tests of grip strength, balance rod, rotorod, and wheel activity; and among C57BL/6J mice, in balance rod, tightrope, exploratory activity, and wheel activity tests. Except for scores of exploratory activity (free versus forced exploration), the test measures tended to be uncorrelated; however, the degree and magnitude of intercorrelation among test scores increased with age. The results underscore the need to consider genotype in the assessment of age-related motor impairments in animal models.     

Enhanced innate immune responsiveness to pulmonary Cryptococcus neoformans infection is associated with resistance to progressive infection

Genetically regulated mechanisms of host defense against Cryptococcus neoformans infection are not well understood. In this study, pulmonary infection with the moderately virulent C. neoformans strain 24067 was used to compare the host resistance phenotype of C57BL/6J with that of inbred mouse strain SJL/J. At 7 days or later after infection, C57BL/6J mice exhibited a significantly greater fungal burden in the lungs than SJL/J mice. Characterization of the pulmonary innate immune response at 3 h after cryptococcal infection revealed that resistant SJL/J mice exhibited significantly higher neutrophilia, with elevated levels of inflammatory cytokine tumor necrosis factor alpha (TNF-α) and keratinocyte-derived chemokine (KC)/CXCL1 in the airways, as well as increased whole-lung mRNA expression of chemokines KC/CXCL1, MIP-1α/CCL3, MIP-1β/CCL4, MIP-2/CXCL2, and MCP-1/CCL2 and cytokines interleukin 1β (IL-1β) and IL-1Ra. At 7 and 14 days after infection, SJL/J mice maintained significantly higher levels of TNF-α and KC/CXCL1 in the airways and exhibited a Th1 response characterized by elevated levels of lung gamma interferon (IFN-γ) and IL-12/IL-23p40, while C57BL/6J mice exhibited Th2 immunity as defined by eosinophilia and IL-4 production. Alveolar and resident peritoneal macrophages from SJL/J mice also secreted significantly greater amounts of TNF-α and KC/CXCL1 following in vitro stimulation with C. neoformans. Intracellular signaling analysis demonstrated that TNF-α and KC/CXCL1 production was regulated by NF-κB and phosphatidylinositol 3 kinase in both strains; however, SJL/J macrophages exhibited heightened and prolonged activation in response to C. neoformans infection compared to that of C57BL/6J. Taken together, these data demonstrate that an enhanced innate immune response against pulmonary C. neoformans infection in SJL/J mice is associated with natural resistance to progressive infection.     

Antibody responses in resistant and susceptible inbred mice infected with Trypanosoma congolense.

Antibody responses were evaluated in inbred mice previously shown to be susceptible (A/J) or resistant (C57BL/6J and B6AF1 hybrid) to infections with relatively avirulent Trypanosoma congolense. Titres and the isotype distribution antibodies specific for the trypanosome variant surface glycoprotein (VSG) were determined by indirect immunofluorescence in sera of mice after primary infections with Trypanosoma congolense and after challenge infections with the same variant following drug cure. The results of these investigations showed that, during active infection, resistant mice made relatively strong VSG-specific IgM antibodies. This isotype also predominated in challenge infections with the homologous variant following drug cure. In contrast, A/J mice made little or no VSG-specific antibody on first exposure to T. congolense. However, these animals were able to produce substantial amounts of protective VSG-specific IgG antibody after multiple-challenge infections with the homologous variant. Substantial titres of VSG-specific antibodies in resistant mice did not influence the numbers of trypanosomes in the first parasitaemic peak as initial parastiaemias were similar in both C57BL/6J and A/J mice. However, C57BL/6J mice cleared parasites in this peak, whereas A/J mice did not. Mice of both strains immunized by infection cure were equally effective in clearing parasites when challenged with homologous trypanosomes. It is clear from the results of this study that antibody is not the sole factor contributing to murine resistance to African trypanosomes.     

Strain polymorphism in progression of aging: changes in CD4, CD8 bearing subpopulations

Polymorphism of age-related changes in CD4 (L3T4) and CD8 (Lyt-2) determinants of spleen and thymus cells was assessed by fluorescence-activated flow cytometry. Cells from mice ranging from 5 weeks to greater than 2 years of age were examined. There is little age-related change in the proportion of CD4+ CD8- splenocytes in A, C57BL/6, DBA/1, DBA/2, and SJL mice (slopes 0.04, 0.06, 0.08, 0.17 and 0.17, respectively, when age in weeks was plotted against % of positive cells). Changes in the composition of the thymus are much more profound: CD4+ CD8+ cells of SJL mice decrease from 70% to less than 10% as the animals age from 5 to 69 weeks (slope -1.03), and in DBA/2 mice from 5 to 110 weeks (slope -0.88). While this decrease in CD4+ CD8+ cells occurs, there is a compensatory increase in CD4+ CD8- and CD4- CD8+ cells; this is a shift in the relative proportion of subpopulations rather than an increase in absolute cell numbers of a particular subpopulation. In contrast to the age-related changes of SJL and DBA/2 mice, there is relatively little change in the proportion of CD4+ CD8+ thymus cells in mice of strains C57BL/6, DBA/1 and A (slopes -0.03, -0.14 and -0.15, respectively).     

Antibody responses induced by immunization of inbred mice susceptible and resistant to African trypanosomes.

We tested the ability of inbred mice that were either susceptible (strain A/J) or resistant (strain C57BL/6 and A/J X C57BL/6 hybrids) to African trypanosomes to produce specific antibodies to trypanosome antigens in the absence of living parasites. This experiment was carried out to eliminate the influence of trypanosome growth or metabolism on immune responsiveness. Mice were immunized with keyhole limpet hemocyanin or solubilized Trypanosoma brucei gambiense, and serum antibodies were measured in solid-phase radioimmunometric assays after primary and challenge injections. Both susceptible and resistant mice showed increases in keyhole limpet hemocyanin-specific or trypanosome-specific immunoglobulin M and immunoglobulin G after immunization. When immunized with trypanosome antigens, resistant mice made qualitatively and quantitatively superior specific immunoglobulin M responses, particularly to the trypanosome major variable surface glycoprotein. Susceptible A/J mice produced good specific antibody responses, although these were predominantly of the immunoglobulin G isotypes. These results show that A/J and C57BL/6 mice respond differentially in terms of immunoglobulin isotype and repertoire in response to injected antigens. The possibility that this differential antibody response influences susceptibility to African trypanosomes is discussed.     

Genetic control of susceptibility to Porphyromonas gingivalis-induced alveolar bone loss in mice

Periodontal disease affects a large percentage of the human population. Resorption of the alveolar bone of the jaw is a pivotal sequela of periodontal disease, because this bone is the attachment site for the periodontal ligaments that anchor the teeth. Using a murine model in which alveolar bone loss is induced by oral infection with Porphyromonas gingivalis, a gram-negative bacterium associated with human adult periodontal disease, we provide evidence suggesting that susceptibility to such bone loss is a genetically determined trait. AKR/J, DBA/2J, and BALB/cByJ or BALB/cJ mice were highly susceptible, while A/J, A/HeJ, 129/J, SJL/J, and C57BL/6J mice were much more resistant. When susceptible BALB/cJ and BALB/cByJ mice were crossed to resistant strains, two patterns were observed. (BALBc/ByJ x C57BL/6J)F(1) offspring were susceptible, suggesting C57BL/6J has recessive resistance alleles, while (BALB/cJ x A/J)F(1) mice were all resistant, suggesting that A/J mice have dominant resistance alleles. These results suggest a tractable genetic basis for P. gingivalis-induced alveolar bone loss and open the possibility of exploiting the mouse model to identify loci important for host susceptibility and resistance to periodontal disease.     

Strain background alters mammary gland lesion phenotype in transforming growth factor-alpha transgenic mice

Whey acidic protein (WAP)-transforming growth factor (TGF)-alpha transgenic mice acquire both cancerous and noncancerous mammary lesions. For this study, we evaluated the effect of mouse strain background on the incidence, latency, and histotype of two noncancerous lesions, hyperplastic alveolar nodules (analogous to typical hyperplasias in women), and macrocysts. These lesions display characteristics of fibrocystic changes observed in breasts of women, and in both mice and humans are associated with an uncertain risk of progression to neoplasia. Virgin transgenic mice of the (C57BL/6J;SJL)F2 background developed very few hyperplastic alveolar nodules and no macrocysts. In contrast, when the WAP-TGF-alpha transgene was carried on the FVB/N strain, congenic virgin transgenic mice acquired both lesion types with approximately 100% penetrance. In the (FVB;C57BL/6J)F1 background, hyperplastic alveolar nodule incidence was reduced to approximately the nontransgenic mouse level, and macrocyst latency was increased dramatically. Crossing into C57BL/6 resulted in elimination of the macrocyst phenotype. Finally, FVB strain transgenic mammary epithelium transplanted into nontransgenic recipients of the FVB/N or (FVB;C57BL/6J)F1 backgrounds displayed macrocyst latency characteristic of the recipient, and not donor, mouse strain. Quantitative real-time polymerase chain reaction analysis demonstrated that, despite the difference in macrocyst incidence between (FVB;C57BL/6J)F1 and C57BL/6 virgin transgenic mice (81% versus 0%), the level of TGF-alpha expression was not different. FVB strain transgenic mice expressed only twofold more TGF-alpha than the other backgrounds. These findings indicate that C57BL/6J modifier alleles inhibit mammary lesion incidence and macrocyst latency in a semidominant manner, and that suppression of lesion development can involve host factors that are independent of mammary epithelial genotype.     

Genetics and senescence. I. Age-related changes in activity and exploration in three inbred strains of mice

Exploratory, locomotor and ambulatory activities were measured in nine independent groups of three inbred strains of mice (BALB/cBy, C57BL/6J and DBA/2J), at three different ages (150 days, 400 days and 750 days). The results show that for two of the three variables, the age-related changes present different patterns as a function of strain. The genetic and/or environmental correlates of the reactivity to aging may thus depend on the behavioral trait under study.     

Strain distribution of mice in discriminated Y-maze avoidance learning: genetic and procedural differences

The current study was conducted to characterize discriminated avoidance learning in mice by using a Y-maze task. In Experiment 1, the task parameters were manipulated, including the amount of time spent in the start arm, the amount of time to make the avoidance response, and the intertrial interval (ITI) using C57 x SJL F1 hybrid mice. Avoidance performance was significantly improved with longer times to avoid the shock and longer ITIs. In Experiment 2, mice from 4 inbred strains (BALB/cByJ, DBA/2J, C57BL/6J, and SJL/J), an F1 hybrid (C57 x SJL), and 1 outbred strain (CD1) were tested with various ITIs. Strain differences were observed in avoidance learning, with BALB, DBA, C57 x SJL and CD1 mice showing significantly better avoidance learning than C57 mice, which were better than SJL mice. These data demonstrate that Y-maze performance is significantly influenced by the genetic background of the mouse and the parameters of the task.     

Variations in age-related decline in striatal D2-dopamine receptors in a variety of mouse strains

To determine the importance of inheritance on the age-associated decline in D2-dopamine receptor number, the binding of [3H]spiperone to mouse striatal membranes was measured in animals ranging from 7 to 104 weeks of age from 5 murine strains (C57BL/6J, C3/HeJ, A/J, SJL/J and DBA/1J). In young mice, receptor number (Bmax) was influenced by genetic background such that C57BL/6J less than SJL/J less than A/J = DBA/1J = C3H/HeJ. A 50-60% decline in Bmax with age was found in all strains except for C57BL/6J. Bmax in the C57BL/6J mice were lower than in the other strains of young animals (7-15 weeks) but remained relatively constant throughout life (measured up to 104 weeks of age). Furthermore, the maximal decline in receptor number was observed relatively early in life (16-30 weeks) and remained constant thereafter. Neither age nor genetic background influenced ligand affinity (Kd). Thus the results of this study suggest that the maximal decline in Bmax for the dopamine receptor occurs before the second half of life and that the magnitude of this decline is polymorphic.