Systemic responses during local viral infections: type I IFNs sound the alarm.

Type I IFNs are well known for their role in controlling virus replication and spread. Type I IFNs produced by the infected tissue also signal beyond the boundaries of the infection to regulate different elements of the anti-viral immune response. Recent reports show that type I IFNs directly condition naive monocytes residing in the distal bone marrow (BM) and induce the expression of effector molecules in memory T cells, before their recruitment to the infected site. In addition, hematopoietic stem cells (HSCs) were shown to enter the cell cycle in response to systemically distributed type I IFNs. These discoveries expand our understanding of the pleiotropic effects of type I IFNs during infection and highlight the critical role of systemic signals in the development of an effective response to a localized viral infection.