**Conflict of interest**

Canadian Blood Services is pursuing patents related to the production and utilization of the described acellular immunomodulatory agents. Canadian Blood Services, a not-for-profit organization responsible for collecting, manufacturing and distributing blood and blood products to all Canadians (except Quebec), is the assignee for relevant patents. MDS, DW and WMT are inventors on these patents. XY has no conflicts of interest beyond being paid by Canadian Blood Services.

*Cells of the Immune System*
