Bovine prion (PrP) and Doppel (Dpl) proteins expression after in vitro leukocyte activation or Dpl/PrP blocking

It has been postulated that Doppel (DpI) and Prion (PrP) proteins have yet undetermined interactions, since DpI is overexpressed in transgenic PrP-deficient mice. In this study we investigated the expression levels of DpI and PrP on lymphocytes, monocytes and neutrophils (PMNs) isolated from bovine blood and incubated (2 and 18 h) with TNF alpha, IL-1, IL-2, IL-8, C5a, IFN gamma, anti-PrP, and anti-DpI antibodies by flow cytometry. The isolation procedures yielded cell populations with high purity, viability and recovery rates. After 2 h incubation, expression of PrP or DpI was altered only in PMNs. These cells overexpressed PrP when incubated with TNF alpha and IFN gamma, and both PrP and DpI when incubated with C5a; incubation with TNF alpha, IL-8 and IFN gamma led to down-regulation of DpI. Lymphocytes incubated for 18 h with IL-2 and with IFN gamma overexpressed DpI. Incubation with the anti-PrP antibody induced down-regulation of DpI in PMNs after 2 h and overexpression of DpI in lymphocytes after 18 h. The differences recorded after 2 h were likely due to redistribution of pre-existing PrP or DpI molecules, while those seen at 18 h were most probably due to increased protein synthesis. The variations seen using the different activators depend on different receptors and/or signaling pathways. These results demonstrate that is possible to alter the expression of DpI and PrP in blood cells in vitro by incubation with either cytokines or anti-PrP antibodies. This opens an interesting opportunity to study the biology of these proteins using in vitro systems.