Taken together with data showing that FRCs respond to host-derived factors during viral infections,37,52 human FRCs respond to TLR ligands,78 and MRC and FDC function is regulated by TLR signaling,33,34 our current results further bring FRCs to the forefront of immune regulation, highlighting their role as sentinels of infection and their activation status as a critical component in immunity that should be considered when designing novel immune-mediated interventions. Here, CD200 is linked to viral infectious disease.