Distribution of amyloid precursor protein and amyloid-beta in ocular hypertensive C57BL/6 mouse eyes

Amyloid precursor protein (APP) and amyloid-beta (Abeta) appear to participate in the pathophysiology of retinal ganglion cell (RGC) death in glaucoma. We, therefore, determined the distribution of APP and Abeta in the retinas of C57BL/6 mice after induction of chronic ocular hypertension.

Junctional adhesion molecule (JAM)-C deficient C57BL/6 mice develop a severe hydrocephalus

The junctional adhesion molecule (JAM)-C is a widely expressed adhesion molecule regulating cell adhesion, cell polarity and inflammation. JAM-C expression and function in the central nervous system (CNS) has been poorly characterized to date. Here we show that JAM-C(-/-) mice backcrossed onto the C57BL/6 genetic background developed a severe hydrocephalus. An in depth immunohistochemical study revealed specific immunostaining for JAM-C in vascular endothelial cells in the CNS parenchyma, the meninges and in the choroid plexus of healthy C57BL/6 mice. Additional JAM-C immunostaining was detected on ependymal cells lining the ventricles and on choroid plexus epithelial cells. Despite the presence of hemorrhages in the brains of JAM-C(-/-) mice, our study demonstrates that development of the hydrocephalus was not due to a vascular function of JAM-C as endothelial re-expression of JAM-C failed to rescue the hydrocephalus phenotype of JAM-C(-/-) C57BL/6 mice. Evaluation of cerebrospinal fluid (CSF) circulation within the ventricular system of JAM-C(-/-) mice excluded occlusion of the cerebral aqueduct as the cause of hydrocephalus development but showed the acquisition of a block or reduction of CSF drainage from the lateral to the 3(rd) ventricle in JAM-C(-/-) C57BL/6 mice. Taken together, our study suggests that JAM-C(-/-) C57BL/6 mice model the important role for JAM-C in brain development and CSF homeostasis as recently observed in humans with a loss-of-function mutation in JAM-C.

Intraperitoneal Echinococcus multilocularis infection in C57BL/6 mice affects CD40 and B7 costimulator expression on peritoneal macrophages and impairs peritoneal T cell activation

One of the most important immunopathological consequence of intraperitoneal alveolar echinococcosis (AE) in the mouse is suppression of T cell-mediated immune responses. We investigated whether and how intraperitoneal macrophages (MØs) are, respectively, implicated as antigen-presenting cells (APCs). In a first step we showed that peritoneal MØs from infected mice (AE-MØs) exhibited a reduced ability to present a conventional antigen (chicken ovalbumin, C-Ova) to specific responder lymph node T cells. In a subsequent step, AE-MØs as well as naïve MØs (positive control) proved their ability to uptake and process C-Ova fluorescein isthiocyanate (FITC). Furthermore, in comparison with naïve MØs, the surface expression of Ia molecules was up-regulated on AE-MØs at the early stage of infection, suggesting that AE-MØs provide the first signal via the antigen-Ia complex. To study the accessory activity of MØs, AE-MØs obtained at the early and late stages of infection were found to decrease Con A-induced proliferation of peritoneal naïve T cells as well as of AE-sensitized peritoneal T cells, in contrast to stimulation with naïve MØs. The status of accessory molecules was assessed by analysing the expression level of costimulatory molecules on AE-MØs, with naïve MØs as controls. It was found that B7-1 (CD80) and B7-2 (CD86) expression remained unchanged, whereas CD40 was down-regulated and CD54 (= ICAM-1) was slightly up-regulated. In a leucocyte reaction of AE-MØs with naïve or AE-T cells, both types of T cells increased their proliferative response when CD28 - the ligand of B7 receptors - was exposed to anti-CD28 in cultures. Conversely to naïve MØs, pulsing of AE-MØs with agonistic anti-CD40 did not even partially restore their costimulatory activity and failed to increase naïve or AE-T cell proliferation. Neutralizing anti-B7-1, in combination with anti-B7-2, reduced naïve and AE-T cell proliferation, whereas anti-CD40 treatment of naïve MØs increased their proliferative response to Con A. These results point at the key role of B7 receptors as accessory molecules and the necessity of the integrity of CD40-expression by naïve MØs to improve their accessory activity. Taken together, the obstructed presenting-activity of AE-MØs appeared to trigger an unresponsiveness of T cells, contributing to the suppression of their clonal expansion during the chronic phase of AE-infection.

E- and P-selectin are not required for the development of experimental autoimmune encephalomyelitis in C57BL/6 and SJL mice

In multiple sclerosis and in its animal model experimental autoimmune encephalomyelitis (EAE), inflammatory cells migrate across the endothelial blood-brain barrier (BBB) and gain access to the CNS. It is well-established that alpha4 integrins are actively involved in leukocyte recruitment across the BBB during EAE. In contrast, the role of endothelial E- and P-selectin in this process has been a controversial issue. In this study, we demonstrate that P-selectin protein can be detected in meningeal blood vessel endothelial cells in healthy SJL and C57BL/6 mice and on rare parenchymal CNS blood vessels in C57BL/6, but not SJL, mice. During EAE, expression of P-selectin but not E-selectin was found up-regulated on inflamed CNS microvessels surrounded by inflammatory infiltrates irrespective of their meningeal or parenchymal localization with a more prominent immunostaining detected in C57BL/6 as compared with SJL mice. P-selectin immunostaining could be localized to CNS endothelial cells and to CD41-positive platelets adhering to the vessel wall. Despite the presence of P-selectin in wild-type mice, E/P-selectin-deficient SJL and C57BL/6 mice developed clinical EAE indistinguishable from wild-type mice. Absence of E- and P-selectin did neither influence the activation of myelin-specific T cells nor the composition of the cellular infiltrates in the CNS during EAE. Finally, endothelial-specific tetracycline-inducible expression of E-selectin at the BBB in transgenic C57BL/6 mice did not alter the development of EAE. Thus, E- and P-selectin are not required for leukocyte recruitment across the BBB and the development of EAE in C57BL/6 and in SJL mice.

L-Selectin-deficient SJL and C57BL/6 mice are not resistant to experimental autoimmune encephalomyelitis

L-selectin has been suggested to play a role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Here we demonstrate that L-selectin(-/-) SJL mice are susceptible to proteolipid protein (PLP)-induced EAE because the compromised antigen-specific T cell proliferation in peripheral lymph nodes is fully compensated by the T cell response raised in their spleen. Transfer of PLP-specific T cells into syngeneic recipients induced EAE independent of the presence or absence of L-selectin on PLP-specific T cells or in the recipient. Leukocyte infiltration into the central nervous system parenchyma was detectable independent of the mode of disease induction and the presence or absence of L-selectin. In addition, we found L-selectin(-/-) C57BL/6 mice to be susceptible to myelin oligodendrocyte glycoprotein-induced EAE. Taken together, we demonstrate that in SJL and C57BL/6 mice L-selectin is not required for EAE pathogenesis. The apparent discrepancy of our present observation to previous findings, demonstrating a role of L-selectin in EAE pathogenesis in C57BL/6 mice or myelin-basic protein (MBP)-specific TCR-transgenic B10.PL mice, may be attributed to background genes rather than L-selectin and to a unique role of L-selectin in EAE pathogenesis in MBP-TCR-transgenic mice.

Differential Effects on Survival, Humoral Immune Responses and Brain Lesions in Inbred BALB/C, CBA/CA, and C57BL/6 Mice Experimentally Infected with Neospora caninum Tachyzoites

C57BL/6, BALB/c, and CBA/Ca mouse strains with different MHC-I haplotypes were compared with respect to susceptibility to Neospora caninum infection. Groups of 5 mice received , , or tachyzoites of the NC-Liverpool isolate by intraperitoneal injection and were observed for disease symptoms. Humoral responses, splenocyte interferon-γ (IFN-γ) production, cerebral parasite loads, and histopathology were evaluated at human end points or the latest at 34 days postinfection (PI). The mortality rates in C57BL/6 mice were the highest, and relatively high levels of IgG1 antibodies were detected in those mice surviving till 34 days PI. In lymphocyte proliferation assays, spleen cells from C57BL6 mice stimulated with N. caninum antigen extract exhibited large variations in IFN-γ production. In BALB/c mice mortality was 0% at the lowest and 100% at the highest infection dose. Serologically they responded with high levels of both IgG2a and IgG1 subclasses, and lymphocyte proliferation assays of surviving mice yielded lower IFN-γ levels. CBA/Ca mice were the most resistant, with no animal succumbing to infection at a dose of and tachyzoites, but 100% mortality at tachyzoites. High IgG2a levels as well as increased IFN-γ in lymphocyte proliferation assays were measured in CBA/Ca mice infected with tachyzoites.

Maternal separation followed by isolation-housing differentially affects prepulse inhibition of the acoustic startle response in C57BL/6 mice

Exposure to chronic stress is associated with an increased incidence of neuropsychiatric dysfunction. The current study evaluated two competing hypotheses, the cumulative stress and the match/mismatch hypothesis of neuropsychiatric dysfunction, using two paradigms relating to exposure to “stress”: pre-weaning maternal separation and post-weaning isolation-housing. C57BL/6 offspring were reared under four conditions: typical animal facility rearing (AFR, control), early handling (EH, daily 15 min separation from dam), maternal separation (MS, daily 4 hr separation from dam), and maternal and peer separation (MPS, daily 4 hr separation from dam and from littermates). After weaning, mice were either housed socially (2–3/cage) or in isolation (1/cage) and then tested for prepulse inhibition in adulthood. Isolation-housed MPS subjects displayed greater deficits in prepulse inhibition relative to socially-housed MPS subjects while socially-housed AFR subjects displayed greater deficits in prepulse inhibition relative to isolation-housed AFR subjects. The results indicate that these treatment conditions represent a potentially valuable model for evaluating the match/mismatch hypothesis in regards to neuropsychiatric dysfunction.

Effect of Cage-Induced Stereotypies on Measures of Affective State and Recurrent Perseveration in CD-1 and C57BL/6 Mice.

Stereotypies are abnormal repetitive behaviour patterns that are highly prevalent in laboratory mice and are thought to reflect impaired welfare. Thus, they are associated with impaired behavioural inhibition and may also reflect negative affective states. However, in mice the relationship between stereotypies and behavioural inhibition is inconclusive, and reliable measures of affective valence are lacking. Here we used an exploration based task to assess cognitive bias as a measure of affective valence and a two-choice guessing task to assess recurrent perseveration as a measure of impaired behavioural inhibition to test mice with different forms and expression levels of stereotypic behaviour. We trained 44 CD- 1 and 40 C57BL/6 female mice to discriminate between positively and negatively cued arms in a radial maze and tested their responses to previously inaccessible ambiguous arms. In CD-1 mice (i) mice with higher stereotypy levels displayed a negative cognitive bias and this was influenced by the form of stereotypy performed, (ii) negative cognitive bias was evident in back-flipping mice, and (iii) no such effect was found in mice displaying bar-mouthing or cage-top twirling. In C57BL/6 mice neither route-tracing nor bar-mouthing was associated with cognitive bias, indicating that in this strain these stereotypies may not reflect negative affective states. Conversely, while we found no relation of stereotypy to recurrent perseveration in CD-1 mice, C57BL/6 mice with higher levels of route-tracing, but not bar-mouthing made more repetitive responses in the guessing task. Our findings confirm previous research indicating that the implications of stereotypies for animal welfare may strongly depend on the species and strain of animal as well as on the form and expression level of the stereotypy. Furthermore, they indicate that variation in stereotypic behaviour may represent an important source of variation in many animal experiments.