Characterization of early transient accumulation of PrPSc in immune cells

•PrPSc transiently accumulates in macrophages during the first 8–12h post-exposure.•The accumulated PrPSc in macrophages is not a de novo product of the cell PrPC.•Cholesterol, cell degradation power and PrPC, are potential factors affecting it.•Macrophages may act as reservoirs for PrPSc if they could not clear it completely.•They are potential risk factors for PrPSc accumulation and intercellular spread. PrPSc is known to elicit no specific immune response and the immune cells are suspected to support its accumulation. In the present study, we investigated the response of some immune cell types to PrPSc to characterize an observed early transient accumulation of PrPSc. After cells were treated with PrPSc-brain homogenate, PrPSc was transiently accumulated for the first 8–12h post-exposure then completely cleared by the 5th day of the experiment. The accumulated PrPSc was not a de novo product of the cell PrPC. Further investigation of this phenomenon revealed some potential factors influencing it. These factors included cholesterol homeostasis, temperature, the degradation power of the cell and the availability of sufficient PrPC. Our in vitro results suggest that immune cells, especially macrophages are potential risk factors for the accumulation and intercellular spread of PrPSc if the complete clearance of PrPSc were not fulfilled.