Although prion proteins are most efficiently propagated through intracerebral inoculation, peripheral administration has caused the diseases kuru, iatrogenic Creutzfeldt-Jakob disease (CJD), bovine spongiform encephalopathy (BSE) and new-variant CJD. The development of neurological disease after peripheral inoculation depends on prion expansion within cells of the lymphoreticular system. Here we investigate the identity of these cells by using a panel of immune-deficient mice inoculated with prions intraperitoneally: we found that defects affecting only T lymphocytes had no apparent effect, but that all mutations that disrupted the differentiation and response of B lymphocytes prevented the development of clinical scrapie. As an absence of B cells and of antibodies correlates with severe defects in follicular dendritic cells, a lack of any of these three components may prevent the development of clinical scrapie. However, we found that scrapie developed after peripheral inoculation in mice expressing immunoglobulins that were exclusively of the M subclass and without detectable specificity for the normal form of the prion PrPC, and in mice which had differentiated B cells but no functional follicular dendritic cells. We conclude that differentiated B cells are crucial for neuroinvasion by scrapie, regardless of the specificity of their receptors.

The adhesive cell surface molecule P 0 is the most abundant glycoprotein in peripheral nerve myelin and fulfills pivotal functions during myelin formation and maintenance. Mutations in the corresponding gene cause hereditary demyelinating neuropathies. In mice heterozygously deficient in P 0 (P 0 ϩ/Ϫ mice), an established animal model for a subtype of hereditary neuropathies, T-lymphocytes are present in the demyelinating nerves. To monitor the possible involvement of the immune system in myelin pathology, we cross-bred P 0 ϩ/Ϫ mice with null mutants for the recombination activating gene 1 (RAG-1) or with mice deficient in the T-cell receptor ␣-subunit. We found that in P 0 ϩ/Ϫ mice myelin degeneration and impairment of nerve conduction properties is less severe when the immune system is deficient. Moreover, isolated T-lymphocytes from P 0 ϩ/Ϫ mice show enhanced reactivity to myelin components of the peripheral nerve, such as P 0 , P 2 , and myelin basic protein. We hypothesize that autoreactive immune cells can significantly foster the demyelinating phenotype of mice with a primarily genetically based peripheral neuropathy.

SummaryAirway access is needed for a number of experimental animal models, and the majority of animal research is based on mouse models. Anatomical conditions in mice are small, and the narrow glottic opening allows intubation only with a subtle technique. We therefore developed a microscopic endotracheal intubation method with a wire guide technique in mice anaesthetized with halothane in oxygen. The mouse is hung perpendicularly with its incisors on a thread fixed on a vertical plate. The tongue is placed with a pair of forceps between the left hand's thumb and forefinger and slightly pulled, while the neck and thorax are positioned using the third and fourth fingers. By doing so, the neck can be slightly stretched, which allows optimal visualization of the larynx and the vocal cords. To ensure a safe intubation, a fine wire guide is placed under vision between the vocal cords and advanced about 5 mm into the trachea. An intravenous 22G Â 1 in. plastic or Teflon catheter is guided over this wire. In a series of 41 mice, between 21 and 38 g, the success rate for the first intubation attempt was .95%. Certainty of the judgement procedure was 100% and success rate was higher using the described method when compared with a transillumination method in a further series. The technique is safe, less invasive than tracheostomy and suitable for controlled ventilation and pulmonary substance application.

Bacteria and viruses may be transmitted to laboratory rodents by contaminated biological materials such as transplantable tumours, cell lines, sera or other biological materials. Biological materials are currently being screened using the mouse or rat antibody production (MAP/RAP) test (serological testing). We decided to test and validate an alternative assay using polymerase chain reaction (PCR/realtime PCR) technology to detect viral contamination directly in biological material. The aim of this study therefore is the validation of our new PCR assays and the comparison of PCR and the MAP test. For 8/14 viruses, conventional PCR was more sensitive and more specific than the MAP test in detecting murine viruses. For 12/14 viruses, the realtime PCR was more sensitive than the MAP test. In 2/14 cases, all three detection methods had the same sensitivity. Furthermore, PCR screening clearly conforms to the principles of the 3Rs as a replacement technique because it eliminates the need for using animals to screen for murine viruses in biological material.

Inherited demyelinating neuropathies are chronically disabling human disorders caused by various genetic defects, including deletions, single site mutations, and duplications in the respective myelin genes. We have shown in a mouse model of one distinct hereditary demyelinating neuropathy (heterozygous PO‐deficiency, PO±) that an additional null mutation in the recombination activating gene‐1 (RAG‐1‐‐) leads to a substantially milder disorder, indicating a disease modifying role of T‐lymphocytes. In the present study, we addressed the role of lymphocytes in the mouse model by reconstituting bone marrow of PO±/RAG‐1‐‐ mice with bone marrow from immunocompetent wild‐type mice. We compared the pathology and nerve conduction in double mutant mice (PO±/RAG‐1‐‐ on a C57BL/6 background) with that in double mutants after receiving a bone marrow transplant. We found that the milder demyelination seen in the lymphocyte‐deficient PO±/RAG‐1‐‐ mutants was reverted to the more severe pathology by reestablishing a competent immune system by bone marrow transfer. These data corroborate the concept that the immune system contributes substantially to the pathologic process in this mouse model and may open new avenues to ameliorate human hereditary neuropathies by exploiting immunosuppressive treatments.