TNF and infection: Given the microglial activation induced by the virus and the temporal progression of the PNN development it is tempting to speculate that activated microglia, TNF, and/or other inflammatory cytokines produced by the glia are critical to the reduced formation of PNNs during the infection, however, our attempts to demonstrate this by using mice lacking TNF or by reducing microglia in the CNS resulted in more severe disease, so it has not been possible to directly demonstrate their role in the delay of PNN formation during infection.