GPR18 and susceptibility to pneumonia measurement: Nevertheless, several of them, SELL, GZMB, and CCR7 (at 3 dpi), and HAVCR2 (TIM-3), TNFRSF9 (CD137), and GPR18 (at 6 dpi) were promptly upregulated for the virulent Lena strain, probably associated with the marked clinical signs, the earlier and stronger peak of replication, and severe pneumonia.