prions

[Martin Cann]

In article <316B77D5.7FEC at pen.gulbenkian.pt>, jcosta at pen.gulbenkian.pt wrote:

> It seems well established that prions "replicate" in the spleen and =
> 
> other lymphoid organs before reaching the central nervous system. If
> we accept the prion model, this should mean that the PrP gene is normal-
> ly expressed in those organs. However, I don=B4t remember having ever read
> any paper on the expression of PrP genes in other tissues than the =
> 
> nervous tissues. Does someone know such studies?
> 
> Another finding that seems to me difficult to reconcile with the prion
> model is the neuronal pathway of spread of infectivity from the spleen
> to the central nervous system. Any ideas about this?

I can't think of any studies that show that the agent actually replicates
in the spleen on its way to the CNS.  Some of the old Scrapie pathology
papers by Dickinson, Kimberlin and the crew probably cover this ground. 
The mode of transmission to the CNS, as I recall from some of this work,
is that the agent uses the Splanchnic Nerve Expressway.  As you probably
know, however, cutting the splanchnic nerve or splenectomy will only
increase the incubation period of the disease and will not affect the
overall disease process and pathology.

For this kind of info the best papers are from the extensive work of the
above authors, and others, from NPU Edinburgh, during the seventies and
eighties.

Martin