SOCS3 and infection: Unlike UVi-MCMV infection of IC-21 cells, which produced no significant up-regulation of SOCS1 or SOCS3 transcripts during the time points observed in these macrophages, UVi-MCMV infection of MEFs caused significant, albeit transient, stimulation of SOCS1 (Fig 5A) and SOCS3 (Fig 5B) mRNA expression at 2 hpi.