Peripheral Primitive Neuroectodermal Tumour (pPNET) in the cervical spine.

Primary spinal primitive neuroectodermal tumours are rare. We present a 45-year-old man with a peripheral primitive neuroectodermal tumour arising in the cervical spine. We believe this to be the first report of this type of tumour in the cervical spine.

Juvenile pilocytic astrocytoma 'pilomyxoid variant' with spinal metastases.

We report a case of juvenile pilocytic astrocytoma of the hypothalamic/chiasmatic region with cerebrospinal fluid dissemination in a 16-month old girl. The tumour in this case had unusual histological features including the abundance of myxoid background, the absence of Rosenthal fibres and the presence of an angiocentric pattern. These features are consistent with the recently described "variant" named pilomyxoid astrocytoma.

The fate of self-reactive B cells depends primarily on the degree of antigen receptor engagement and availability of T cell help.

Self-reactive B cells from tolerant double-transgenic (Dbl-Tg) mice coexpressing hen egg lysozyme (HEL) and rearranged anti-HEL immunoglobulin genes have a relatively short life span when compared to normal B cells, irrespective of whether they are exposed to antigen in multivalent membrane-bound form (mHEL-Dbl-Tg mice) or soluble form (sHEL-Dbl-Tg mice). The factors responsible for determining the fate of these B cells after encounter with self-antigen were investigated using a cell-tracking technique in which anti-HEL Ig-Tg spleen cells were labeled with the intracellular dye 5-carboxyfluorescein diacetate-succinimidyl ester (CFSE) and injected either into non-Tg recipients or a variety of HEL-Tg hosts. In non-Tg recipients, HEL-binding B cells persisted in the circulation and could be detected in the follicles of the spleen for at least 5 d.