Figure 2.

Secondary lymphoid organs allow controlled OV replication (exemplified by spleen)

Unique properties of MMMs determine their permissiveness to OVs: due to anatomical location, these cells accommodate high concentration of systemically injected OVs; (2) Usp18 upregulation blocks type I IFN-mediated response in MMMs. Transient viral replication in CD169+ cells is crucial for eliciting rapid antiviral responses by (1) secreting type I IFN and other cytokines; (2) recruiting inflammatory cells; (3) priming T and B cell responses; and (4) multiplying antigen for activation of neighboring dendritic cells. Moreover, MMMs can transfer cell-surface-associated infectious virions to B cells and DCs, contributing to the infection of these cells. Virus replication in DCs further increases type I IFN production in the lymphoid tissues and improves the efficiency of antigen presentation. Additionally, B cells may transfer OVs directly to follicular DCs, enabling boost response in immunized hosts.