To confirm that cells of haematopoetic origin contribute to the excessive IFN-α in vivo in 6:2 Tky/05 virus infected mice, we FACS purified CD45-positive cells from lungs harvested 2 days post infection and performed qRT-PCR for viral RNAs and for IFN-α and IL-6 mRNAs. The gene discussed is PTPRC; the disease is infection.